Possible nova in Centaurus, PNV J13544700-​5909080, 03 Dec 2013

[Rob_K]

This PNV is up on TOCP, object confirmed with recent visual obs giving a naked-eye object at around mag 5. Discovered by John Seach, NSW, Australia.
http://www.cbat.eps.harvard.edu/unconf/followups/J13544700-5909080.html

I managed a rough spectrum last night under poor conditions of low altitude, thin (and thick!) cloud and a howling gale. Star Analyser grating and Canon 650D at 200mm.

Also crop from 200mm widefield image, same conditions.

Cheers -

[Suzy]

Hi Rob, great to see that image!
I'd like to use it on the heads up for the IIS fb page if you don't mind?

I've just come across a finder chart for anyone who's interested in going after it. Looks an easy catch :D.

http://varsao.com.ar/Nova_Cen_2013.htm

[Rob_K]

You're welcome Suzy, although the image is a very poor one. There is a better one posted in the other thread. :thumbsup:

Cheers -

[malclocke]

Nice work Rob, especially given the altitude and conditions.

Can I ask if you were preregistered for CBAT? I sent my spectrum but it hasn't shown up.

[Rob_K]

Thanks Malc. Yes, I'm registered. It's a simple matter to apply (follow instructions on TOCP main page) and they email you a username & password. They can take a while to reply as it's not an automated process.

Cheers -

[malclocke]

Hi Rob,

In case you haven't seen it, both of our spectra are cited in the IAU CBET #3732. I'm not subscribed but someone from Canterbury University astronomy department let me know.

It's my first telegram so I'm pretty stoked :)

Sun is setting here now, patchy cloud. Fingers crossed I'll get another shot tonight.

[Rob_K]

Thanks for that Malc, and congratulations on the mention! Pity CBETs aren't freely available, would love to get a copy.

Looking good here although the wind's pretty fierce.

Cheers -

[Andrew Pearce]

Hi All

This is probably the brightest southern nova since Nova Velorum in 1999. This morning I made it mag 4.6 at Dec 3.842UT and a recent observation from Argentina has it now at mag 4.3. So we'll know soon on this side of the globe as to whether it has continued to brighten.

Cheers
Andrew

[Rob_K]

This morning I made it out to be V=4.5, naked-eye observation (04.74 Dec 2013 UT). Attached is another spectrum, amazing the difference a clear sky & a bit of altitude make!

I'll attach some pics to the other thread.

Cheers -

[Suzy]

Ah! Thanks Rob- I missed the other thread. I've found it and posted your image you have there. It's a fantastic guide!

[Jon]

Good stuff, Rob and Malc.

I haven't even seen the little blighter yet - wall to wall cloud in Canberra. But I have my SA 100 poised and ready, and am desperately hoping that the guys in Holland making the L200 spectrographs get them rolling out before too long - I have one in order.

The French spectroscopy crowd must be gnashing their teeth.

[malclocke]

Well, the cloud has arrived here tonight so hopefully it has left you behind.

I'm about to pull the trigger on buying an L200 too, although as this is the second once in a lifetime nova in the past few months I'm expecting a drought after mine arrives :)

[Rob_K]

Another clear night here and there appear to be significant changes in the spectrum of the nova. Terry Bohlsen, where are you?! Rather than the emission lines that have been showing at H-alpha & H-beta, absorption lines are evident. I re-shot it several times with the same result - calibration is not perfect but close enough. SA100 grating with Canon 650D & 200mm lens, stack of 15 subs.

Cheers -

[Merlin66]

Managed to get a few spectra tonight - still to process, but you can see a P Cygni profile at Ha.
12A/pixel with the Baader grating+Genesis.

[Merlin66]

What a difference a day makes....
The emission around Ha and Hb have lost their P Cygni profile and become truncated in the blue.....
12a/pix

[h0ughy]

do you think it is brighter?

[Merlin66]

David,
Yes I do.
Never measured yesterday, but the spectrum in the same exposure, 30s is much brighter this morning........

[h0ughy]

this is what i got this morning (http://www.iceinspace.com.au/forum/showpost.php?p=1039942&postcount=49)

[Rob_K]

Yep, I found the same Ken. In general, within the resolution available to me, from 3-6 Dec the Ha & Hb emissions flattened gradually while the adjacent absorption lines deepened, peaking 6 Dec with a flat Hb and a fairly flat, slightly broader Ha line. On the 7th the P Cygni profile is gone and the hydrogen emission lines are re-asserting themselves. Will be interesting to keep following it on a night-to-night basis. :thumbsup:

Cheers -

[Jon]

Here's my SA100 spectrum from 7 Dec 17:40 UT. Possible He and N emissions associated with an He/N nova?

[Rob_K]

Nice work John! Cloudy here last night but I had a go anyway. There was a thin clear band in the SE and after waiting half an hour for it to pass over the nova position it had narrowed and I only got one rather sad cloud-affected sub.

Anyway, despite horrendous noise I added it to the series but it doesn't say much other than the Ha & Hb emission lines appear to exist! No weight should be put on any other lines showing in the spectrum unfortunately.

Looks like it might be cloudy again here tonight but I'll be ready if there is a break.

Cheers -

[malclocke]

As I'm sure most of you have seen, Christian Buil has requested spectra of the nova for a database on the ARAS site. Below are the details on submitting your spectra for addition to the database, I'd like to encourage everyone to do so and prove to the northerners that we are up to the job!

[malclocke]

Hi Ken,

Are you able to catch anything with an L200? With Terry out of action we are severely missing out on higher res data for this nova.

Malc

[Rob_K]

Well ARAS won't be getting my wonky spectra to "discuss the limitations". Christian is a nice guy and the members of ARAS do some incredible work, but they are typical of amateurs when they get obsessed with the pursuit of excellence. Just like astrophotographers, make it seem as complex as possible in order to 'own' the field. The limitations of spectra like mine don't need discussion, they are well known. Every spectrum is useful to some degree as long as its limitations are recognised.

This sort of stuff is exactly what turns people off from engaging in spectroscopy. Obviously, all you are going to produce is junk unless you pay the big bucks for the hardware and engage with the complex software! ;)

A much healthier approach is to encourage more people to engage in basic spectroscopy with Star Analysers & similar, and offer pathways to take it further if people are so inclined. Variable star astronomy is facing a similar watershed. There has been a big push for the accuracy offered by CCD photometry but like higher-res spectrometry it's an elite activity requiring decent equipment and a long learning curve. The number of visual observers has dropped dramatically (why bother?) and the grass roots from which CCD photometrists would otherwise naturally arise is evaporating.



We're definitely missing Terry! :thumbsup:

Cheers -

[Rob_K]

Cleared late, luckily! Here's my spectrum from tonight, SA100 grating with Canon 650D & 200mm lens on Vixen Polarie, 20 x 15 sec at ISO 6400, F/5.6. Very strong and gusty wind affected all subs.

Hydrogen lines growing stronger but still can't get much at the H-gamma line - pretty much at the edge of the camera response, maybe to do with altitude as I picked it up the one time I did an early morning session on it, when it was considerably higher.

Cheers -

[Jon]

Set the alarm but it's blanket clouds for me I'm afraid. Here are my stacked and corrected SA 100 spectra for Dec 6 and 7.

Cheers
Jonathan

[malclocke]

That's a shame Rob, you're spectra are some of the best I've seen produced. Would you submit them to a database if it wasn't run by ARAS?

Malc

[Merlin66]

Typically, when you need the Spectra-L200 it's lying in bits on the bench! With all the component testing for the new batch, being done by Mark at JTW Astronomy, it hampers my own observing.
Having said that, I'll start re-assembling it tonight and set it up at least with the Genesis....
Got up last night, and was clouded out....
Let's not get overly concerned about ego's and "big toys" syndrome....we can all contribute to the best of our abilities...that should not stop us trying to produce the best data we can - the basic methodology is sound and should be used.

The latest news is that professional spectra have identified the nova as an FeII type....

ATEL #5639 ATEL #5639
Title: Spectroscopic observations of Nova Cen 2013
Author: L. Izzo (Sapienza Università di Roma and ICRANet), E. Mason
(INAF - Osservatorio Astronomico di Trieste), L. Vanzi, J. M. Fernandez,
N. Espinoza, K. Helminiak (Pontificia Universidad Catolica de Chile),
M. della Valle (INAF - Osservatorio Astronomico di Capodimonte)
Queries: luca.izzo@gmail.com
Posted: 8 Dec 2013; 12:39 UT
Subjects:Optical, Nova
We report optical spectroscopy observations of the recent outburst of Nova
Cen 2013 = PNV J13544700-5909080, obtained with the 0.5 m telescope at
the Pontificia Universidad Catolica de Chile Observatory with the PUCHEROS
echelle spectrograph on 2013 December 6.33. The observations cover the
spectral range between 425.5 and 726.0 nm at a resolution of \sim 0.025
at 500 nm.
The observations shows typical features of Fe II spectra, with the Fe II
5169, which is blended with Mg I (2), as the brightest non-Balmer line.
We detect many other absorption lines and P-Cygni associated with Fe II
lines of the multiplets (74, 54, 49, 48, 46, 38, 37 and 27) and possible
multiplets (43, 41, 25 and 20) as well. We report also the presence of
lower ionization transitions as Ti II (70 69, and 39) and Cr II (44 and
30), and other transitions as Si II 6347 and 6371 AA, from detection of
their P-Cygni absorptions. The velocities measured from the P-Cygni profiles
for all these lines are v_{rad} \sim 408 +- 10 km/s. Similar velocities
are measured for the Na I doublet absorptions.
The H-alpha line shows a flat P-Cygni profile with absorption extending
up to -1300 km/s, while the Doppler broadening of the emission line extends
to +700 km/s. The profile is not structured and shows a triangular shape.
On the other hand, the P-Cygni profile of the H-beta is more sharp, with
minimum at around -450 km/s, showing an other possible minimum at -1200
km/s, which we however associate with the presence of Cr II (30), detected
also at 4824 and 4876 AA.
It is interesting to note that from the widths of the Na I doublet, we
have preliminarily estimated an E(B-V) = 0.11 +. 0.08 from Poznanski et
al. (MNRAS, (2012), 426, 1465) and E(B-V) = 0.14 from Munari & Zwitter,
(A&A, (1997), 318, 269), which suggest a low extinction and a not large
distance for the nova. We will continue to monitor the spectroscopic evolution
of the nova in the following weeks and suggest to continue to follow-up
the nova, particularly at different wavelengths.

[Rob_K]

Sorry Malc, what I meant was that ARAS won't be getting my spectra because I work only in jpegs, that's all. I wouldn't 'withhold' them.

The way ARAS approach things is that only spectra that can produce good, clean quantitative data are useful (pursuit of excellence). I disagree - we're only amateurs and we all have time, money & interest limitations that determine how far we're comfortable going with any branch of astronomy.

Low-res spectra with SA gratings can still be very useful qualitatively, regardless of whether they're in FIT/S or jpeg form, especially for identification purposes (eg recent CBET) or flagging changes.

Cheers -

[Rob_K]

Tonight's spectrum of V1369 Cen (Nova Centauri 2013), moonlight-affected. Had to shoot early as clouds were building. SA100 grating with Canon 650D & 200mm lens on Vixen Polarie, 28 x 14 sec at ISO 1600, F/5.6. H-alpha emission line is getting stronger, FeII lines also appear stronger. Nova should be reddening visually. I could barely make it out naked eye because of moonlight and low altitude. Last night it was very clear naked-eye after moonset, probably not much different tonight.

Cheers -

[Merlin66]

Rob,
Glad to see you managed to get another spectrum.
Clouded out again down here...
I have the Spectra-L200 set-up ready.....

[Rob_K]

Good luck Ken, you must be champing at the bit! :thumbsup:

Cheers -

[pvelez]

Where is Terry B? I hope he is on hols or something

My LISA is on its way back from France after some repairs to its guiding optics. When I mentioned the nova to the Shelyack guys they burst their boiler trying to get it back to me ASAP.

Great work team - hope to contribute in a week or 2

Pete

[Chochawker]

Hello everyone.

As my first post, I thought I would share the rough results from my first look at the nova.

This was captured at 3:20 am from Sydney using an SA100 and DMK 41 through a 10" Goto Dobsonian.

[malclocke]

Yep, Terry is on holiday I believe, see http://spectro-aras.com/forum/viewtopic.php?f=5&t=742

Hopefully your LISA will return soon and you can stand in :)

Malc

[Rob_K]

Nice job Malcolm! :thumbsup: Hope you can get a few more.

Cheers -

[Jon]

Nice work, Rob. The FeII at 5169 us as clear as day, now we know what it is.

[malclocke]

BOOM! That's quite a first post! Well done, hope we see more from you soon.

I've just finished my session for tonight, will post tomorrow once I've processed them.

[Rob_K]

Mine from tonight (12:39, 11 Dec 2013 UT, or 11:39pm 11 Dec local time), getting harder with moonlight. Also cloud about - nova was sitting in a thin, relatively clear band of sky between the horizon and heavier cloud above.

SA100 grating with Canon 650D & 200mm lens on Vixen Polarie, 21 x 17 sec, ISO 6400, F/5.6. Nova at just under 2.5-deg altitude, imaged from White Cliffs, NSW, Australia.

Cheers -

[Jon]

Indeed! Nice work.

Here's mine from this morning - a single sub. I'll stack 12 and tidy up later today.

I'm still interested what the emission feature is around 4500 A, now we know it's not an He/N nova. I'll do some research.

[Merlin66]

Clouded out until about 2:30am
Baader 207 l/mm on Genesis (4"f5) clearly shows the Ha/ Hb emission which have increased over the past couple of days.
I did manage to set-up the Spectra-L200/1800 but PHD let me down and clouds moved in.
I recorded some images around Ha. let's see what they show.....

[malclocke]

Some clear weather last night, although seeing was fairly average. Propped my eyelids open for a little later this time and got a slightly better result with the increased altitude (abot 18 degrees). Used Alpha Cir for calibration which is possibly not an ideal choice.

Also attached an image showing the colour evolution from my data so far.

[Chochawker]

Thanks for the kind responses. :)

I've finally had a chance to attempt a better calibration including instrument response.

This version attempts to identify a few additional features.

[Rob_K]

Excellent Malcolm! :thumbsup:

Tonight's low-res spectrum attached, little change other than the H-alpha emission continuing to strengthen. SA100 grating with Canon 650D & 200mm lens on Vixen Polarie, 25 x 13 sec, ISO 6400, F/5.6. Nova at just under 2.5-deg altitude, imaged from White Cliffs, NSW, Australia.

Cheers -

[Jon]

Here are my spectra of the nights of 11-12 December UT - the last two mornings - showing increase in all emission lines.

Cheers

Jonathan

[Rob_K]

Nice job Jonathan! Here's mine from tonight (13.58 Dec 2013 UT, or 12:48 am, 14 Dec 2013 local AEDST time, UT+11), SA100 grating with Canon 650D & 200mm lens on Vixen Polarie, 30 x 13 sec, ISO 6400, F/5.6. Nova at 8-deg altitude, bright moonlight, imaged from White Cliffs, NSW, Australia.

Cheers -

[Merlin66]

Thanks for sharing!
Clouded out again down here in Melbourne!
The nova appears to be brightening again and the Ha emission seems to still be on the increase.....

[Jon]

Clouded out here, too.

The re brightening seems to have peaked on Thursday night and a slow fade started, but it's hard to tell from the AAVSO light curve as there's so little photometry being done. From our spectra we see Ha increasing.

But at the same time the B-V value is decreasing -i.e. the star is getting bluer. This seemed odd at first. But I'm guessing that when a significant part of the star's flux is Hydrogen emission, the usual BV shorthand for star colour doesn't work so simply. It's fine for normal stars that basically follow black body radiation curves; if B is brighter than V then V will also be brighter than R; there's a slope across the spectrum determined by the star's temperature. But here, with both Ha and Hb contributing more and more, B-V will decrease, but V-R will increase; that is, the star will be getting both bluer and redder. Rather than a Planck black body curve there will be a saddle-shaped curve with a dip centred around about 5600 A, right in the middle of the V band.

I wish I had an R filter! Not to mention IR for the dust phase to come. Santa, are you listening?

[Rob_K]

Tonight's low-res spectrum attached (14.54 Dec 2013 UT), SA100 grating with Canon 650D & 200mm lens on Vixen Polarie, 34 x 13 sec, ISO 6400, F/5.6. Nova at 4.3-deg altitude, bright moonlight, imaged from White Cliffs, NSW, Australia.


Cheers -

[Merlin66]

Not getting any sleep, but watching a solid cloud bank sit above us.....
Seriously, anyone with a spectroscope/ grating should be observing this Nova..a chance of a lifetime to record such a bright object.

[Jon]

Some visual observers in non-cloudy parts of the world had it at 3.2 yesterday! Re-brightening beyond its initial maximum. Is that usual?

[Jon]

Nice, Rob. FeII at 5169 really bright now.

[Merlin66]

http://arxiv.org/pdf/1004.3698v1.pdf

This gives some nova light curve data for comparison.
There can be a "pre-max halt" - Cecilia Gaposchkin "The Galactic Novae", p10.

[malclocke]

Last night's effort. Balmer lines are still increasing and continuum seems to be increasing slightly in the blue.

If the previous maximum was a pre-max halt, there could be a continuing rise of 1 to 2 mags ...

[cometcatcher]

Seemed brighter this morning, though that could just be better skies or my vision less blurry.

[Terry B]

Easy question. Im in Niseko in Japan. Constant snow and no nova.
Im back after boxing day and will take spectra after then.
You guys are doing very well with the SA.
Terry

[pvelez]

Make sure you leave some snow Terry - I'm up there in mid-Jan.

My LISA is repaired and only a few days away. Will post when I have something useful

Pete

[Merlin66]

Pete,
Out of interest....what was the issue with your LISA?

[Rob_K]

Tonight's low-res spectrum attached (15.65 Dec 2013 UT or 2:31 am, 16 Dec 2013 EDST, UT+11), SA100 grating with Canon 650D & 200mm lens on Vixen Polarie, 18 x 10 sec, ISO 6400, F/5.6. Nova at 17.5-deg altitude, bright moonlight, imaged from White Cliffs, NSW, Australia (30.8-deg S).


Cheers -

[Merlin66]

Rob,
Appreciated!
The Ha/Hb and Fe still very prominent....
Cloudy again in Melbourne.

[Jon]

And am I mistake on or is there growth in the NaI D lines around 5890?

[Merlin66]

This could be the HeI (D3) "flash" - 5876A??????

[Jon]

Here's my SA100 spectrum of an hour ago. Stack of 12x40s with a 10"SCT f/6.3 and Atik 383L+. Also a comparison with 12 December.

The FeII lines are stronger than my last spectrum on 12 Dec. Apart from the huge growth in Ha, if anything the new feature is an emission line that could be OI at 7773. There could be OI around 6300-6360 but at this resolution it's hard to unpick them from the FeII(74) lines.

Cheers

Jonathan

[pvelez]

3 issues - all duly fixed. It arrived back from Shelyak today so I can test it tonight.

The calibration unit has a spring loading which flips a mirror across to cover the guide optics when taking flats and neons. The spring wasn't properly set in place and so the screen would not retract properly. I had to take the LISA off the scope to push it out of the way by hand.

The other 2 related to the guide unit. I found that guide images were of poor quality and stars showed signs of aberration off-axis.

Turns out there were 2 problems. The first was the slit mirror was misaligned. The second was the guide optics were out of kilter meaning that only stars at one corner of the guide image were able to be focused. So when stars were set for imaging, I couldn't tell whether they were on or to the side of the slit.

I was able to play with the mirror but the guide optics meant that I couldn't correct the image.

Looking at the test shots that Shelyak sent back, I should see a remarkable difference. Francois has been very attentive and helpful.

Looking forward to some clear weather to test this tonight

Pete

[pvelez]

What time is best for observing this nova? Please tell me its a sensible hour

Pete

[Jon]

Nope. :-)

You could catch it visually with binoculars now or a telescope in the dawn twilight around 4.45. But if you want to image it in any way you'll need to get cracking by about 3.30 I'm afraid.

[pvelez]

Bugger

I go riding at 5.30am on Wednesdays but 3.30 is a bit tougher

You guys are impressive

Pete

[mithrandir]

Pete, depending on your horizon it could be any time. It doesn't clear my roof until about 1am and by 4:30am the sky is getting too bright for a good view.

If you have a recent version of Stellarium enable the "Bright Novae" plugin, restart, wait a few seconds for it to update the data, hit F3, type "Nova Cen and hit Enter.

[Rob_K]

Last night's low-res spectrum attached (16.58 Dec 2013 UT), SA100 grating with Canon 650D & 200mm lens on Vixen Polarie, 18 x 13 sec, ISO 6400, F/5.6. Nova at 9-deg altitude, bright moonlight, imaged from White Cliffs, NSW, Australia (30.8-deg S). The black area on the left of the bar was an overlapping 'spectrum' of a tree in moonlight!

Cheers -

[Merlin66]

No excuse for the delays....
This is the Lo-res spectra I recorded earlier....
Shows the dramatic increase in the Hydrogen emission and the FeII....

[Rob_K]

Nice work Ken! :thumbsup:


Cheers -

[Merlin66]

Thanks Rob! Appreciated.
Check your PM for a proposal....
The AAVSO light curve shows the falling brightness....

[Jon]

Here are four spectra from 6 December (initial maximum) to 16 December showing the evolution of the lines to I think the level of resolution achievable with my SA100 and system.

Apart from the obvious Balmer emission lines (and hint of P Cygni visible in the 6/12 Ha line profile), and the clear evolution of the FeII lines, there is what I think is NaI at 5889. Also strong growth of an emission line around 7773 - is it the OI triplet?

Cheers

Jonathan

[malclocke]

Looking great Jonathan!

Do you think you will submit them to the ARAS database? Mine are looking awful lonely there, and represent a very low bar to exceed :) I'm clouded out again tonight.

I wonder if that feature at ~7770A might be second order contamination, or do you have something in place to cut that?

[Jon]

Cheers Malc. Yes, I think I'll send them to ARAS once I fathom the format. I also need to get registered there - my messages to Francois seem not to be getting through.

Ah yes, second-order contamination. Good point. I've only just got a mono CCD quite recently, and was doing spectra with a DSLR. So everything up beyond 7000 A is new territory for me. I've already made a clanger with the telluric absorption at 7600 that Ken kindly put me right about.

[Merlin66]

2am and heavy milky cloud....bumma!
Re BeSS submissions...
John's BASS project software
http://uk.groups.yahoo.com/neo/groups/astrobodger/info

John has now included a section on the preparation of the necessary BeSS fits header and gives guidelines which include checking the final format. Worth looking at.
If you need help just let me know.

[Jon]

Quick and dirty spectrum from this morning. I'll stack and polish later, :-) this is just one 3s sub. The reason it's only 3s is cause as you can see the Ha line is going nuts. So I'm starting to take two set of images: one where everything is in linear range, and another set where I let the Ha line saturate so as to get more detail with the other lines. I hope this is a reasonable thing to do :-)

[Jon]

thanks Ken. Jeez, you're not having much luck with the clouds down south, are you?

[Merlin66]

Whoooooooooooo!!!!!!!:eyepop::eyepo p:
What a difference a day makes!
Looks like there are few (!) options available - super saturate the Ha in longer exposures or many, many short exposures and add them.
Fantastic stuff - well done Jon!

[cometcatcher]

Wow that Ha spike is amazing. It looks about mag 5 in the visible, what magnitude would it be if we could see Ha? (If that makes any sense)

[Jon]

Actually, I thought of taking an image of the star field using my Ha narrowband filter, just to get a sense of that.

[Merlin66]

IMHO I think, looking at the continuum, most of the visible energy is in the hydrogen emissions....let's say 80% in the Ha =<0.5 mag below current visual.

[cometcatcher]

In it's present state with that huge Ha spike, why doesn't it look more red? Last night in binos I couldn't see any colour.

[Merlin66]

FINALLY got some clear skies!!!!!!
Still processing some medium res spectra (Spectra-L200/300, R=1000)
I'm not sure that the Ha is as bright (?) (spectra to follow)
The region around Hb looks interesting - need to confirm the emission lines.
I'm just thankful to have had a hour or so between the clouds.
More to follow.

[Jon]

Nice to have some medium res stuff at last! More clouds on the way I'm afraid, Ken.

Here's mine of this morning. Certainly the Ha line is less prominent relative to the other emission lines, I think.

[Rob_K]

Great work guys! I'm finally home again but haven't even unpacked my gear yet - cloudy, and probably continuing...

Cheers -

[Terry B]

Ken
Im sure this would be the case.
With nova Del, I was able to take 30sec exposures early on when there was mostly a continuum but it was about mag 4
By the time it had dropped to mag 7 I was restricted to 5 sec exposures to prevent saturation of the Ha line. I was stacking 30 x 5 sec exposures using Isis with good results.
Im back in Oz but won't be home til the 26th. Then I have to be awake enough to get up at 3am to take some spectra. It probably will only happen on the weekend. I hope the clouds will stay away then.
Terry

[Merlin66]

Clouded out down here...did anyone manage to get a spectrum last night???

[malclocke]

Still under it down here, haven't got anything since the 14th :( Hoping for some clear weather over the holidays.

Have just bought the second hand L200 that was recently advertised on the astro_spec list :) Maybe it will get here in time to get some data on this nova ...

Interesting developments with the AAVSO light curve, looks like it may be on the up again. Looking at the literature oscillations during the decline are quite common, and it looks like this could be what this one is up to.

[Jon]

No. Wall-to-wall clouds. Clouding over again now, looks like it will be no break in the clouds in Eastern Australia till Christmas.



Nice, I've got one on order with JTW. Fingers crossed it will come soon.



Interesting data from the visual guys. Looks to go up, then comes straight back down. All within tolerance of simple estimation error. I was as keen to do some photometry as I was to take some spectra. I have a little 3.30 am routine: 12 SA spectra, shift the camera to the guidescope, 12 V exposures, 12 B exposures, by which time twilight is upon us ...

[Jon]

Sigh. More clouds.

The thing is up and down like a roller coaster. Back up to 4.5. The good news is, according o Payne-Gaposchkin, these oscillations in the early decline phase are almost always associated with the slower novae. So it should be around for a while.

[Merlin66]

A clear night down here for a change....
Imaging Nova Cen in the background.
The Ha still looks very strong and the Fe lines at Hb seem a little more prominent. I'm also taking some spectra around the Na region....
Stay tuned!

[Shark Bait]

I was lucky to catch it between the clouds this morning. My comments are in the other thread.

What would you place its magnitude and colour at?

[Rob_K]

First chance since 16 Dec and I managed to obtain another spectrum last night. H-alpha line remains dominant (although it graphed poorly??); NaI line at 589nm and the various FeII lines have increased in relative intensity; H-gamma is weak but it could reflect the camera response, weak at that end.

The nova was a relatively easy naked-eye last night but because of the low altitude and sky gradients in that direction I didn't attempt an estimate. Definitely brighter than the mag 5s though.

Also attached is a Xmas card for those to whom it matters - to all others, have a safe and happy holiday season! :thumbsup:

Cheers -

[Jon]

Rob - love both your images :-). Look at the FeII lines! Rivalling the H beta.

Very little media coverage of this nova. I'd expect a few "Star of Bethlehem" pieces;-)

[Jon]

Here's a quick one from this morning

[Merlin66]

Rob, Jon,
Well done guys!
Weather permitting we seem to be keeping track of the nova.
I have some spectra which will show the same emissions as Jon's - hope to process them later today.

[Jon]

OK guys, here's a stacked and cleaned up spectrum from this morning. Easily my best capture with the SA100. I've done a fair bit of research this morning on what I may be seeing. So here goes:

1) The Balmer lines remain prominent. However, they are less so relative to the continuum than on 19 December. This corresponds with a rebrightening of the nova - as the nova brightens, the SA100-measured Balmer lines decrease in relative intensity.

In a study of V5558 Sgr (2007), another nova with a series of rebrightenings after maximum, Tanaka et al (2011) (http://arxiv.org/pdf/1105.1614v1.pdf) found that the absorption component of the Balmer P Cygni profiles increased as the nova rebrightens. This is because the rebrightening is owing not to increased temperature, but to increased density, mass flow and photospheric radius of the stellar wind.

The SA100 does not have sufficient resolution to capture both absorption and emission components. The net effect of an increase of the absorption component would be a diminution of the measured emission component, as here. This seems to be an interpretation that is at least plausible.

2) The FeII emisison lines are extremely prominent across the spectrum.There is also evidence of CaII, NaI, NII, and possibly HeII and CII. These latter are less convincing, but are consistent with a FeII nova at this stage.

3) There is no evidence of any forbidden lines. Not unusual, but see below.

4) Perhaps the most interesting feature of the spectrum is OI at 7773. OI at 8446 is present in nearly all novae spectra, but OI 7773 can only form in conditions of a relatively dense wind. Williams (2013) (http://arxiv.org/ftp/arxiv/papers/1208/1208.0380.pdf) discusses this in detail and proposes the 8446/7773 ratio as a means of classifying the wind environment of different novae. Williams suggests that where the 8446/7773 ratio is low (as here), and the wind relatively dense, then forbidden lines are (unsurprisingly) slower to emerge.

So there is is - even from a SA100 spectrum there's a bit of evidence from the rebrightenings and the 8446/7773 ratio that this is a nova with a particularly dense wind.

[Rob_K]

Thanks Ken, and nice work again Jon! You're doing well and it's great to see areas that are way outside the response range of my camera! :thumbsup:

Here's mine from last night.

Cheers -

[Merlin66]

I've been working my way through Steve Shore's comments/ notes on Nova Del as a reference source:

The two first pages (Francois is still working on them) http://www.astrosurf.com/aras/novae/Nova2013Del.html (http://www.astrosurf.com/aras/novae/Nova2013Del.html)

The notes are downloadable from : http://www.astrosurf.com/aras/novae/Images_NovaDel2013/SteveNotes.pdf (http://www.astrosurf.com/aras/novae/Images_NovaDel2013/SteveNotes.pdf)

[Merlin66]

Here are some results for review and discussion...

I have a medium res around Hb (showing P Cygni?) and the He and Fe emissions (look at the shape of the peaks - absorption?)
Moved across towards the Na region - again some profile detail...
Finally around the Ha (again some P Cygni?) - the emission is still so strong, I zoomed into show some of the underlying detail....
Processed with BASS Project.

Feedback welcome....
(EDIT: The R value on the charts is incorrect. It should be R=1650)

[malclocke]

Fantastic work Ken!

Do you have a velocity for the P cyg profiles?

[Merlin66]

Malc,
I haven't finished the processing....hopefully we'll have some answers soon....

[malclocke]

Well, don't expect anything from me for the next wee while :(

[Merlin66]

Yeah..... any excuse!;)

[Merlin66]

Based on my measures of the P Cygni profiles, I get 1796 Km/s at Ha, and 1789 Km/s at Hb. Seems consistant....say 1790 Km/s +/-

[Terry B]

Well done Ken.
I might be able to get something over the next few days. Not keen on 3am though.:P

[Merlin66]

Terry,
I understand!!
The "Indian Alarm Clock" seems to work for me......;)

[Jon]

Here is my spectrum from this morning, and a comparison with yesterday. Little change from yesterday. Actually, I'm quite pleased how the two spectra line up - it shows that the small undulations I'm rather optimistically identifying as lines are real, not noise :-)

[malclocke]

Interesting. ATEL #5639 (http://www.astronomerstelegram.org/?read=5639) showed up to ~ -1300 km/s and I get a figure consistent with that from Rogerio and Tasso's spectra, up to the point where their spectra lose the p cyg profile, see attached.

Is an acceleration here an expected part of the evolution?

[Merlin66]

Malc,
I could be wrong....
the difference at Ha was 39.3A and Hb 29A. When you plug in these numbers I get the 1790 Km/s....
I'm collecting more data as I type (thanks to Teamviewer!!) - let's see what that shows.
I've also made contact with Steve Shore who wants to helps us. Drop me an email for details.

[Jon]

Everything I've been reading suggest that it all gets pretty complex around now. Ken's emission lines all show a consistent saddle shape to the peak - look at the FeII lines 490-530 nm in particular. Payne-Gaposchkin talks about these (p.63) as a consequence of the ejects not being a uniform sphere, but instead a ring or jets. So, if the ejecta were concentrated in a disk inclined at an angle of 40 degrees to us, that might account for what we are seeing, if I've read P-G correctly.

Furthermore, the red-ward peak of the emission line saddle is slightly stronger than the violet side. The geometry of all this is I'm sure telling us something significant, and I'd be really interested in what Steve had to say about it.

However, in terms of measuring the Doppler shift of the P Cygni profile - which is what we are debating - the is a simple question. What do you measure - the distance between the centre of the absorption line and the blue-ward or red-ward peak of the saddle, or he barycenter of the entire emission line?

I guess what I'm saying is, from everything I've read, the simple model for understanding Doppler shifted P Cygni lines - a uniform expanding sphere of gas, with emission lines from the radially-expanding component and (blue-shifted) absorption lines from the component coming directly towards us - pretty quickly breaks down in the case of novae, where the ejects are more complex.

I'd be keen to help out with whatever I can as far as Steve is concerned. Particularly once my L200 arrives.

Cheers

Jonathan

[Merlin66]

KISS....
I followed the details in "Spectroscopy - key to the stars", Keith Robinson.
Page 121
"...simply from the difference in wavelength between the center of the emission line and that of the absorption line. Simply plug in this wavelength difference into the simple Doppler effect formula to get the wind velocity"

I was using John's BASS Project which calculates the max and min flux value wavelengths......
I should re-run the profiles through Vspec for comparison.

I agree the Fe profiles look "saddled"

[Jon]

Makes sense. Sorry, Ken, I wasn't trying to be difficult :-). My head is spinning from all the stuff I've been reading about this. Just trying to account for why there might be different measurements of velocity between you and Malc.

I've just been reading Steve Shore's "Spectroscopy of Novae - a users manual". He talks about changes in he ejecta velocity, but also changes in what parts of the ejecta become visible owing to changes in the optical thickness of the ejecta with different phases ... I can't pretend I understand all he's saying!

But I liked the bit where he said to take a look at YouTube videos of slo-motion explosions of Hydrogen bombs to get a general idea :-)

[Merlin66]

Jon,
Not a problem. We're all learning our way here......

[malclocke]

I'm not sure whether it is best to measure the fitted centre of the emission line or the text book wavelength. I'd be tempted to use the latter, and that is what I have used, because I don't really understand the cause of the asymmetry of the line profiles.

I believe (could well be wrong) that the end of the blue wing of the absorption gives the maximum velocity, which should represent the material that is heading directly towards us and hence the ejecta velocity.

Due to my general lack of knowledge of the details I'm treating all of my measurements with a high level of uncertainty.

[malclocke]

You are definitely not alone there Jonathan. I find some of Steve's write ups assume a little more prior knowledge than I currently have at my disposal.

By the way, I see your spectra have made it into the ARAS database, nice work.

[Merlin66]

Keith Robinson's "Spectroscopy -key to the stars" has a good chapter "Glowing Vortices-Accretion Disks" - p105>
Goes some way to explain the peaks and blue/red wings.......

[Merlin66]

Clear through until about 3:30am....
Screwed up the camera settings and ended up with 2 x 2 binning! This reduced the resolution to around R=1600.
The P Cygni at Ha and Hb give around 1500-1600 Km/s.
No dramatic changes that I can see......

[Rob_K]

Very nice job Ken! FWIW, here's my low-res spectrum from last night.

I've had a light-globe moment with my spectra, particularly the relative intensity of Ha & Hb showing in my graphs of V1369 Cen. I shoot only in jpeg and the method I use to create the graphs is to grayscale the bar spectrum and save as FIT files using Registax. The red of Ha, no matter how intense, is never going to be 'less grey' than the cyan of Hb so the graph simply won't display the relative intensity of Ha that shows in the line or bar spectrum.

The answer would be to shoot in RAW and do whatever it takes to transfer the luminosity rather than shade to a bar spectrum and hence to the graph. But unfortunately that's a step I'm unwilling to take. Aside from the fact that my poor old computer has convulsions just dealing with full-size jpegs, I'm quite happy with my level of commitment equipment & time-wise to spectroscopy. I have lots of other keen interests in astronomy (comets, comet search, nova search, RNe etc) - I'm not retired, have a very busy life and there's just no time left! ;)

So you guys might just have to put up with my wonky spectra! :P :lol:

Ken, I'll contact you shortly off-forum. :thumbsup:

Cheers -

[Terry B]

I have finally achieved a spectra of this nova. Getting up at 3am isn't one of my favorite things to do.:P

It is very bright. Simultaneous photometry yielded V= 4.27
It is easily naked eye from my observatory.
Because it is is so bright I had to use very short exposures to prevent saturation. I took 26x 3 sec exposures and have processed them in Isis.
I have also flux calibrated the result.
It still has PCyg features.

Terry

[Jon]

Nice stuff Terry.

I found a couple of articles about novae that rebrighten, suggesting that the P Cygni profiles recur when the brightness peaks. Links are in a long post of mine from a couple of days ago.

I had V=4.2 in my photometry of Saturday morning. Looks like this third "maximum" may have peaked - but who can tell with this thing?

[Merlin66]

Great stuff!!
Well done - good to see you back on stream, even at 3am!
Certainly shows the current detail........

[Shark Bait]

Aside from human error, is there normally a means to explain the difference between photometry results and careful visual magnitude assesments? :question:

0400 to 0435 hrs AEST Sun 29-12-2013 (1800 to 1835 hrs UT Sat 28-12-2013)

This morning I observed Nova Cen 2013 through 7x50 Binoculars and I placed it between Mag 4.0 to 4.1 - Nova Cen 2013 was still visible along with Mu1 Crucis (Mag 4.0) at 0435 hrs local time when the fainter stars were washed out and lost from sight.

I tried something different to get an accurate gauge on the magnitude of Nova Cen 2013. I waited for the morning twilight to wash out the sky and let the stars used for comparison fade from sight. The nova was definetely brighter than Lamda Crucis (at Mag 4.59) and HIP70069 (at Mag 4.28).

[malclocke]

Welcome back Terry :)

I'm just going over my results from the 11th and 14th and trying to do a better reduction to resubmit to ARAS. You'll notice my spectra have a ~ in the validation column at http://www.astrosurf.com/aras/Aras_DataBase/Novae/Nova-Cen-2013.htm - this is shorthand for 'these are crap!'

Just thought I'd share a comparison between my results (black) and Jonathan's (red) from the 11th. Overall not a bad match I think, apart from mine getting a bit lost in the blue end.

[Jon]

A good fit, Malc. You're getting more detail than me on 11th. My collimation was a bit out - I redid it before the 16th and got much better detail. Plus, I could take longer exposures as the nova wasn't as bright.

[Jon]

Good question, Stu. When Terry and I talk about "V Mag" we are talking about an image taken through a Johnson V filter. This is essentially a green filter with a passband centred on about 5300 A - the dead centre of the human visual range. So for average stars the measured V mag will be quite close to the estimated Visual mag. Terry and I also took B (Blue) measurements, which were around 4.4. So this nova has a B-V value of 0.2 at the moment. B-V is a shorthand and quantitative measure of the colour of a star: typically B-V around 0 is a fairly blue star, while B-V of 1 or more us a fairly red star.

The problem is, this nova is neither average nor typical! A lot of the light is coming from the Ha line in the red part of the spectrum, and a fair bit from the Hb and other lines in the blue. These are both outside the main passband of the V filter. So I'd expect Visual estimates to be a notch or two brighter than the V measurements. But it is very hard for even experienced visual observers to get closer than 0.1-0.2.

The AAVSO gas an excellent manual for visual observers. http://www.aavso.org/visual-observing-manual. I hope you are reporting your observations to them!

Cheers

Jonathan

[Shark Bait]

Thanks again Jon. I was a little concerned that my best efforts to visually pin down Nova Cen 2013's magnitude were still different to the figures you were all getting.

To be honest, sending my visual estimates to the AAVSO did not occur to me. I am surprised that visual is considered a valid measurement when photometry and spectroscopy can remove the subjective element of the data collection. I will follow up on the link that you provided and will consider sending my observations.

Regards,
Stu.

[Jon]

Stu, is it weren't for the visual observers, we wouldn't even have a light curve for this thing! For the record, the last visual record uploaded, a few hours ago from South Africa, was by Peter Wedepohl, an experienced observer with over 2000 logged observations going back to 1998. He had it at 4.1, same as you :-)

Photometry is not as an exact science as it may seem. My last measurements in the same session spanned 4.18-4.27, and each of these was a stack of 5 exposures. The problem is that the object is so bright. I'm having to take no more than 5s subs through my little 80mm guidescope - using my main scope would saturate the star in an exposure of less than a second. Even with the guidescope, I can only take 5s exposures, which mean that seeing, scintillation and even the camera shutter can all distort the recorded brightness, and that the signal to noise ratio is low.

Second, photometry works by comparing the measured target's pixel intensity with that of comparison stars of known magnitude, ideally similar magnitude (and colour!) to the target and in the same field. For this object we have to use two 7th magnitude comp stars, which is stretching the capability of the method to be really accurate - I have to make sure the nova doesn't saturate or get close to the non-linear response threshold of my camera, but that means the comp stars are faint, subject to scintillation, and have barely-acceptable SNR.

I hope that makes sense! The short version is - for an object this bright, frequent visual observations are invaluable and can close to photometry in accuracy if done well.

Now, when it fades to mag 12, that will be another story ;-)

[Terry B]

A comparison of flux calibrated spectra of V1369 and Nova Del. The V mag isn't exactly the same. It shows how much further evolved V1369 is at a similar magnitude compared to Nova Del. This nova is much brighter.
http://i566.photobucket.com/albums/ss109/TCB168/V1369vsNovadel_zps8fdc5697.png

[Terry B]

I was wondering what star you guys are using to correct instrument response (if you are doing so).
I experimented with 2 stars last night but decided on HD118978. It is close by the nova so at a similar airmass. It is a B9III star with clear H lines.
It would be sensible for all observers to use the same star for instrument response.
Any other suggestions?

[Jon]

Indeed. 18/8 was two days after Nova Del's maximum. The emission lines present on 14/8 had all but disappeared, and had yet to reappear. The best spectral comparison date with Nova Cen would be 7 or 8 Dec.

We are currently 23 days after maximum for nova cen. It has fallen from 3.5 to 4.1 in that time. The equivalent for nova del was a fall from 4.2 to 7.3 23 days after maximum.

Del was quite a fast nova. But Cen is not only brighter; it's much slower.

[Merlin66]

Bumma - clouded out again!
Only managed to get a sequence around Hb before they moved in....
I'll process and upload later.
Anyone else have better success???

[Merlin66]

Well, well, well..........
Just started to process the spectra from last night (around Hb) and the Hb, Fe profiles have completely changed!!
I'm glad I managed a second series of exposures (20 x 30s) - they confirm the changes....H gamma also looks brighter??
Hope to post later....
The Na region was almost a wash out due to the cloud....there may be something...let's see.

[Jon]

I wish I knew what was going on with these re-brightenings. I've been reading all I can. It's clear that there is evidence of spectral changes during these "maximums" in other novae. There seems to be very little available spectra of these sort of novae!

It looks as though we are at the peak brightness for the third "maximum" and that brightness is declining now. Does this correspond with the changes you observed in the Hb and Fe lines, Ken? I wonder ...

[Merlin66]

The attached image shows what looks like secondary (?) P Cygni dips as well as the "saddle tops".
I'll get a copy to Steve Shore for comment......

[Jon]

Fantastic! Do share what Steve says.

The saddles are also slightly different from two days ago - now the blue end is stronger than the red.

These double P Cygni profiles maybe suggest two "shells" of ejecta, moving outward and different velocities?

[Merlin66]

Certainly will do!
I'm having some "problems" preparing the BeSS fits header (I'm currently working in BASS Project - trying to get it to work well with slit spectra)
Hopefully it will all come together later today and I'll upload the data I have to Francois and the ARAS team.
I'm definitely not smart enough - even after reading Gaposchkin and Steve's notes to figure out what is happening.
I think we're getting some very interesting data, I hope it helps.

[malclocke]

Hi Terry,

This is a good question and I've been reluctant to make any suggestions due to lack of experience. I looked at François T's spreadsheet of recommended stars and picked Alpha Cir as it had a very similar altitude at my observation times and was quite bright (3.2). It does have spectral peculiarities though. The spreadsheet has a selection of A and B class stars with low E(B-V) values which I believe makes them good candidates for calibration.

It seems to me that getting a similar airmass for the calibration star is crucial here as the nova is so low. Given how close Terry's star is to the nova in angular terms it may be the best choice as a standard.

For the record, here is a selection of stars from the spreadsheet, and the approximate local time when they each is at a similar altitude to the nova. They all have a fairly large angular separation from the nova.

HD113902 00:00 5.7 B8V
HD115823 01:30 5.4 B6V
HD117150 03:00 5.0 A1V
HD118991 03:30 5.0 B8Vn

[Terry B]

Very interesting Ken.
It was cloudy here last night and I have to work this week during the day so 3am is a no go til next weekend.

[Jon]

The thing was so bright I used Beta Centauri the first time I grabbed a spectrum :-)

After that I used HD118978, as Terry suggested.

[malclocke]

That's fantastic, almost a carbon copy of fig 3.1 from Gaposchkin - https://archive.org/stream/TheGalacticNovae/Payne-gaposchkin-TheGalacticNovae#page/n63/mode/2up

[malclocke]

I've calculated the E(B-V) for HD118978, it is 0.04 which is quite low. I think the reason it doesn't feature on François' spreadsheet is that it is luminosity class III rather than V. But B9III is in pickles so we have a reference to work from.

So all in all it looks like choice, and it seems most people are using it already :)

[Merlin66]

Malc,
Missed that one!
As you say - a textbook copy.....makes me feel better!:thumbsup:

At least the equipment is working well - PHD/Lodestar, Spectra-L200/300, ATiK314L and the Neon and Filly ref lamps as well as the NEQ6 and EQMod. All the problems are operator related! ;)

[Merlin66]

The earlier cloud bank has moved away....
I should be able to get a full set of Hb/Na/Ha spectra.
Only problem now is lack of sleep!!

[Merlin66]

The attached spectrum covers from Hb to the Na doublet.
No major changes from the 30th.

[Merlin66]

Cloud thickened as the morning progressed. No success.
Did any one else manage to obtain some spectra??

[Jon]

I'm away on holidays at the Central Coast. I've got my DSLR and SA100, but haven't managed to use it. It was just naked-eye visible last night - my estimate was 5.3-5.5. Fading fast.

EDIT: oops, no, got my comp star wrong. More like 5.0+. Still fading, though.

[Merlin66]

Hmmm
Another cloudy morning.....
I hope others are have more success.

[Chochawker]

No luck here.
On the rare occasion that the weather has cooperated, work has managed to get in the way. :(
At least it is giving me time to read through all of the interesting things posted here.

[Terry B]

I also have cloud. Clear days and cloudy nights.:shrug:
It should clear up tomorrow or Saturday so I should be able to get another spectra then work permitting.

[malclocke]

Nothing but cloud here since forever. Amusing myself by reading Steve Shore's notes from V339 Del and playing with everyone else's data :)

My L200 is on it's way from the US, obviously the clear skies are waiting for it's arrival. Haha.

[Merlin66]

Very frustrating!!
I'm reviewing the possible effects of the spectral flats on the continuum....and finalising my notes on the necessary focusing accuracy for the telescope and the collimator/imaging lens in a slit spectroscope.

[malclocke]

And working on submitting your spectra to ARAS of course ;)

[Terry B]

Amazingly it is still too hot tonight to try to use my cameras. It is 32deg at 10pm. This is 15deg hotter than usual. I wouldn't be able to cool them enough even with water cooling. Also the water container in my observatory is probably sitting at 30deg as well so not much use really:P. I will have to hope it is better tomorrow.

[h0ughy]

its 24 here at the moment , very humid and the sky is murky, with clear patches. i was hoping to get something this morning

[Merlin66]

The banks of cloud in the south seem to have moved through - looks like a long night!
Should be able to collect some data.

[h0ughy]

Still 24 here and very humid, so much so we have a fog? Imaging is out however I can see it without binos slight averted vision. Looks a tad dimmer than a few nights ago looking at the sc I would say between 4.7 and 5 ish

[h0ughy]

Well what a difference a few minutes makes. Full on cloud and southerly change her now and it's lovely , not so much for viewing nova though.

[h0ughy]

Well it's a dry southerly. Can seethe pointers and crux clearly as too the nova. Amazing as twilight is well underway to sunrise. Hope someone did well. There is a slight colour to it when compared to hadar and crux. Wished I setup to image it now, oh well?

[Shark Bait]

It appears that V1369 Cen (Nova Cen 2013) is getting brighter again. I watched the nearby stars fade with this mornings twilight. It is at apparent Mag 4.3 with no obvious colour through binoculars.

I logged a report in the visual thread. Nova Cen 2013 just keeps on giving.

[Rob_K]

Great to hear you're back on the job Terry, even if it's going to be intermittent! :thumbsup:

I've been getting an odd low-res spectrum and have attached one from last night (3 Jan 2014). No graph, I realise now that it's pushing jpeg data into places it shouldn't go! I notice a few lines that seem to be firming up but am having difficulty identifying some of them. Calibration isn't perfect but I think there's a Ca I line at 612nm and possibly an Fe VII line at 572nm. There's a line at around 628nm and even with calibration issues I can't see how it would be O I at 630nm. There's also a line at around 530nm and Fe I emissions at 527/533nm seem way too far off. Advice, opinions welcome.

Cheers -

[Jon]

Hi Rob,

Nice work. I expect the 530 Nm line is the FeII 5317 A line. The strength of FeII continues unabated - this is the phase Steve Shore calls "the iron curtain" phase, which hasn't lifted yet. Look at the strength of FeII 4924, for instance. Although in your spectrum this is closer to 490 Nm.

The line you have at 612Nm line could well be FeII at 6148. In fact, it's hard to see what else it could be. But there's a pattern here - these lines are showing up on your spectrum about 2 Nm blue of where they should be. That's pretty consistent with the sorts of velocities we've been seeing in the red and blue shift - up to 1500 km/s, which is 3 Nm at the wavelength of Ha. Calibration is a bit tricky - if you look at your Hb, it runs from about 482 at the blue end of the absorption line to 488 at the red end of the emission. Again, I suspect this is a bit blue of where it should be; I suspect it would be worth recalibrating. Maybe use the NaI at 5892 as a reference, and set that point towards the blue end of the emission line.

[Rob_K]

Thanks Jon, that makes a lot more sense. :thumbsup:

Cheers -

[Merlin66]

Looking good for tonight - cleared up nicely!
I'm still processing last nights results, hopefully tonight will compliment them.

[Terry B]

I had a lovely clear evening and took a number of spectra of Be stars. Went to bed at 11pm and got up at 3am to find a thick peasoup fog. Not a star to be seen so nothing from me last night unfortunately.

[Merlin66]

Bumma!
I know what it's like....very frustrating.
I did get the usual Hb/Na/Ha spectra last night, but still working on them.
Hopefully I'll upload the backlog later today.

[Jon]

Looking forward to them!

Having another look at Rob's spectrum, it seems that we may be seeing the emergence of [OI] at 6300 and 5577. This is expected at this stage. This nova seems strong in OI, from what I'm reading this being a feature belonging to the wind coming of the secondary red giant energised by the initial nova outburst. But I don't understand the relationship between OI and the forbidden [OI] - the next thing on my reading list :)

[Jon]

Also the [NII] line at 5755. This often comes at the same time as [OI].

[malclocke]

Finally got some time to process my efforts from 2 nights ago (3rd Jan), my first spectrum of 2014 :)

H_beta has really dropped in relative intensity, on a par with the FeII lines. Anyone else seeing this?

I have a spectrum from the 4th to process too, might not get to upload that until tomorrow.

Brightness is on the up again(!), AAVSO visual estimates coming in around 4.5, up from around 5.0 3 days ago. There seems to be a pattern emerging in the oscilations of slow rise, fast decline.

[Jon]

Crikey!

I'm back at home from holidays now so will be able to get a spectrum this morning.

[Rob_K]

Nice work Malcolm, and good luck Jon! :thumbsup: Intermittently cloudy here, might get a break.

Cheers -

[Jon]

Interesting. Hb definitely less intense compared to the nearby FeII and Ha, as Malc found. Also FeII at 5018 less intense than FeII at 5169 - it was a different story a week ago.

I'm wondering if what we're actually seeing here is an artefact of the SA100 resolution. There seems to be complex structures of emission and absorption now visible, as the outer layers of the ejecta become optically thin. I wonder if the SA100 is just capturing a lessened emission when in reality what's there is a strong emission and a strong absorption just next door?

Have to wait for Ken's spectra to be sure.

[Terry B]

I took a spectra this morning about 2:30 so at an airmass of 1.9
With a quick check at the time, the Ha is much stronger and there seems to be a widening of all of the lines especially towards the blue. I will have to check my calibration but the telluric lines were identical with my last spectra so it should be real.
I will process it properly tonight when I'm home from work.

[Merlin66]

Sorry for the delay.
The attached spectra cover the various regions from 31st Dec/4th and 5th Jan
I also show a comparison of the changes around the Hb and Fe lines.
Comments welcome.

[Merlin66]

here's the Hb area from the 31st to the 5th.

[Terry B]

Great Ken
Here is last nights data compared with 28/12/13.
I have 2 versions. The first is flux calibrated.
The magnitude last night was V= 4.88 compared to 4.27 on 28th so it has dropped somewhat.
The overall flux has reduced including the output at Ha and Hb.
When I graph the spectra as "relative intensity" there has been a increase in the intensity of all the emission lines compared to the continuum.

[malclocke]

Nice work Terry. I'd just like to commend you on the fact that these are flux calibrated, it is quite incredible.

Finally managed to process my effort from the 4th, see attached. Little change from the 3rd.

[Rob_K]

Great stuff Ken, Terry, Jon & Malc! Here's mine from last night, just to add a bit of colour LOL! :P

Terry, I gather you are a bit pushed for time but there hasn't been much B-V-R photometry done on the nova. Have you been getting any data in conjunction with your spectra?

Cheers -

[Terry B]

Rob
I have taken simultaneous photometry on the 2 nights I have taken spectra. The data for B and V have been uploaded to AAVSO. I took R and I data last night as well but I don't have comp data in those bands. Hopefully it will appear in the future.
Terry

[Jon]

Gosh, lots to ponder. Some really intricate P Cygni and multiple emission/absorption patterns in the hi res spectra from Ken and Terry.

Here's mine from the last two nights. [OI] at 6300 and 5577 strengthening, and [NII] at 5755.

These lines are clear on Terry's, and on Ken's from the same time, but not so much on Ken's of 31/12. Interesting.

[Jon]

Nice to see our B and V sitting nicely within 0.02-3 mag of each other. :)

It would be good for the AAVSO guys to provide a bit more comp data about now ...

[Merlin66]

Glad to see all this data coming together!
Steve Shore has asked for all data to be uploaded (BeSS fits format) to the ARAS forum for further discussion. He's also suggested recording the line velocity profiles for various emission lines......details to follow.

[Rob_K]

Excellent Terry, I kind of suspected you might have it all in hand! :thumbsup:

Cheers -

[Merlin66]

An extract from Steve's recent emails:

Leaving the data in wavelength masks important information. Put
instead, in velocity, you convert the profile into a map of the ejecta.
In the sense that the radial velocity depends on radius, for fixed
orientation relative to the observer, the higher velocity parts of the
profile are from the outer portions of the ejecta (this would be true
for a wind too, as in a classical P Cyg profile).
By doing this you also can compare profiles of different ions,
for instance seeing how the Balmer lines change (which is the same ion,
neutral hydrogen) or the changes in the resonance line of Na (the D
lines) compared with [O I]6300, say, which is a forbidden line and
traces lower density gas.
Once you've done this simple step you start to see a lot of the physics,
and the time dependence starts to make sense because you can
compare across excitations and ionizations.


Try comparing Halpha and Hbeta, that's the simplest to get a feel for
the optical depth variations in the absorption component. There's also
a progression -- the H-beta absorption is at a lower velocity than
H-alpha because it's formed (from our point of view toward the ejecta)
further inside (in other words, you have to look geometrically deeper
to get the same optical depth). Then Na I 5889.95,5895.92, when it's
observable He I 5876, the multiplet Fe II 4923, 5018, 5169, and the O I
6300, 6364 doublet. When it's observable, N II 5755. These should be
a good start.

[Jon]

Ken, is there anything in Steve's emails that might account for the brightness fluctuations?

Bloody thing's on the rise again: V 4.62, B 4.76, B-V same as last night, 0.14

[Merlin66]

No, I've asked the question, but no comment as yet.
I'm about to change over to the 1200 l/mm grating see how that goes.
(I don't want to go to the 1800 l/mm at the moment...)

[Rob_K]

More colour from last night, FWIW. I have been shooting RAWs lately but haven't had time to do anything with them (I'll send when I can Ken).

Cheers -

[malclocke]

Who is in the loop for these emails Ken? I'd love to see them.

[Merlin66]

Malc et al,
At the moment they're just personal emails between Steve and myself - having said that I've no problem sharing....
I get the feeling he really want's to work through the ARAS forum - like he did for the Nova Del....

Let me know if you want copies of the current emails.....

This is his reply re the magnitude fluctuations:

"" The most interesting feature of the light curve, I think, is its
similarity to a few other classical systems (historical ones) that have
shown "oscillations" during the peak and early stages of decline. The
one that is rather striking is a relatively recent nova, V5588 Sgr
2009. It was quite faint, there are VERY few spectra, but the two
Christian managed to catch are similar to the V1369 Cen spectra now
and, more to the point, don't show any hint of Ne so it was likely a CO
type. The only spectra were from the optically thick stage (at least
the only ones I can see, Fred Walter has sequestered the others from
SMARTS although I';ve seen them, low resolution but enough to be
interesting in the optically thin stages). These oscillations, if you
extend the light curve to months instead of weeks, seem to increase in
their intervals. This was seen,. for instance, for GK Per 1901
although not realized at the time, and with the earlier optical
(visual) data you can never be quite sure. There were also multiple
peaks in other classical systems, CP Pup for instance, that were
actually relatively fast. And then there's T Pyx, everything odd a
nova can do was and is done by this one. But the interesting feature
of its light curve is that there isn't this same sort of quasi-periodic
behavior in the multiple peaks, they seem to come on a timescale but
not so nearly regularly.

What this is, at this stage, would require too much speculation. But
being a theorist by training, there are two clear possibilities (still
speculative). The thermonuclear source could still be exciting
ejections, but on this timescale it's very hard to believe unless it's
an indication of intermittent accretion, again something that's hard to
compute and harder to credit. Or there could be -- already -- a
thermal instability of the WD that's causing a variable illumination of
the ejecta as the effective temperature changes. This is more
reasonable, the timescales are kind of ling but not impossible, but
that's something I'm still working out. It's been suggested that after
the ejection event there is a relaxation of the WD so perhaps that's
going on here and the angle of viewing is favoring a view of the
phenomenon. The objection is that this is a rare thing, while other
novae would be expected to show it unless it's something specific to
the WD mass.

Anyway, these are still idle thoughts in the early stages. One should
remember that although the nova event is brief in normal astronomical
senses, the behavior is individual (even with regularities) and
patience is always a virtue.

I hope this helps. ""

We really need to organise/ arrange with Francois and the ARAS forum to collect and publish the data as well as a running commentary from Steve.

[Rob_K]

Thanks Ken. I find it interesting that he mentions:

" The most interesting feature of the light curve, I think, is its similarity to a few other classical systems (historical ones) that have shown "oscillations" during the peak and early stages of decline. The one that is rather striking is a relatively recent nova, V5588 Sgr 2009."

That one struck me as something unusual. It was quite dim (not reaching mag 11) and was in one of my usual nova search fields. I actually gave the alert on the second big spike through vsnet-alert because it suddenly became visible again in my frames. It disappeared again but later I seemed to get a faint trace of it again. Not entirely confident in what I was seeing, I did notify Mike Simonsen (AAVSO) who had been observing it - turns out it was the third spike! I posted the AAVSO light curve in the other thread a week or two back, link here:
http://www.iceinspace.com.au/forum/showpost.php?p=1044675&postcount=135

But you'll see it's not quite the same behaviour as V1369 Cen.

Cheers -

[Jon]

Thanks for these, Ken. Really interesting stuff from Steve.

Who here us a member of the ARAS forum? I've tried to register repeatedly but get nothing back from them. I've tried to email Francois about it but he doesn't reply. Any suggestions?

Cheers

Jonathan

[Rob_K]

No suggestions here Jon, I tried it too with no success. :shrug:

Cheers -

[Jon]

Interesting stuff in your colour version, Rob. 5577, 5755 both clear. I wonder what's going on with the strong absorption line at about 561 Nm? It's showing up in mine of last night, too- much deeper than the previous night.

[Merlin66]

I'm a ARAS "member", but I still can't get a reply from Francois or Christian on the submission of fits files......

[malclocke]

One thing to be sure of is to use your full name as your username when you sign up. I tried to sign up with my usual username of malclocke and got nowhere. I think they maybe get a lot of spam sign ups. See http://spectro-aras.com/forum/viewtopic.php?f=16&t=31

Can't offer any advice on lack of response to emails though. François is certainly around as he has been posting to the forum and mailing lists.

Keep trying. I thought I was being stonewalled at first, but that was definitely not the case.

[Terry B]

I'm also an ARAS member and had an email from Francois today after I sent him my latest spectra for the database. He is certainly around.
I don't remember a problem with joining up but it was a long time ago.

[Rob_K]

Thanks Mal, I've tried again. :thumbsup:

Cheers -

[Merlin66]

Well, so far so good (I'm sure that's what the Captain of the Titanic said about 11:30pm!)
I've changed over to the 1200 l/mm grating
So far I've collected some Ha data and (hopefully) the Hb is being done as I type....
Let's see...

[Merlin66]

Hmmm
Now working at R=4040....
Could have done with more exposure time....
The Hb region is the first processed...showing the now "standard P-Cyg" in both the Hb and Fe lines.
I've run a velocity graph based on the Hb (4861A) showing the larger absorption is still around the 1600Km/s
Feedback/ comments welcome.

[Jon]

Nice.

As Malc will vouch for, I've been quite strident in another place about how the SA100 spectra are far too low-resolution to be used for velocity calculations, given that a single pixel makes a difference of +/- 300 km/s. Nevertheless (don't the ll anyone) I ran the velocity calculation on a nice P Cygni profile that was present on the Na D line in my spectrum of a few days ago, and got ... 1600 km/s :-)

[Merlin66]

Jon,
We have all got to make the best use of the equipment we have...
I'd never knock the gratings...my ol' Baader 207 l/mm has paid for itself over and over.
Things just get a little more complicated when you move to slit spectroscopy....and working with reference lamps/ calibration etc. (As Mark is about to find out :eyepop:)

[Jon]

Don't get me wrong - my SA100 is easily the best $150-odd I've spent in astronomy. If you'd told me six months ago that I'd be observing the emergence of forbidden [OI] lines in the thinning ejecta of a nova in Centaurus, as it happens in real time, using a tiny bit of kit I ordered from Bintel on a whim, I'd have laughed at you.

Don't you get the feeling that there's this enormous, cataclysmic cosmic event going on in our celestial backyard (I mean, it's almost on our bloomin' FLAG, for heaven's sake) and the five of us have got a ringside seat to watching astrophysical history in the making!

As you can tell, I'm excited :-)

[Merlin66]

Adding to the general confusion...
Here's a noisy Na region....
Not sure what's going on here.....

[Jon]

Here is tonight's spectrum. The [OI] and [NII] lines keep growing.

The continuum seems to slope towards the blue. I've noticed it doing that during the maxima of its rebrightenings. I wonder what's causing that effect?

[Merlin66]

Jon,
Well done.
I was hampered by high cloud - retired gracefully!

[Jon]

I managed to get 6x10s spectra - then sat up waiting for a gap in the cloud to snatch B and V. No luck - I retired crankily!

[Terry B]

Cloudy here and forecast to stay like it til Saturday. I just wish it would rain as well. We are very dry.:sadeyes:

[Merlin66]

Here's the Ha region from the 8th.

[malclocke]

Looking good Ken. I wonder if that's another lower velocity absorption feature starting to show? Time will tell.

Are you confident with the wavelength calibration? The zero point in your velocity plot is way off the centre of the curve, whereas it is quite central in your Hb plot.

[Merlin66]

Malc,
The calibration was based on four neon lines....should be good.

[Merlin66]

Tonight is very warm, but lookin' good.
I hope everyone is sharing this brief spell of cloud free weather.

[Merlin66]

Hmmmm
That didn't go well!!
I upped the exposure to 40 x 30s to get better SNR, and "re-adjusted" the grating and slit assembly to get more consistent positioning on the CCD. The results: Rubbish!
Almost three hours of wasted time - I honestly should have recognised the symptoms - problems with PHD (which I very rarely have) and abnormal low subs signal....
Bumma.

[Terry B]

Ken
Why use short exposures. If the S/N is low then try 5 min exposures. You will see straight away if the signal is low and not waste as much time.

[Merlin66]

Yeah, point made!

[Jon]

Here;s this morning's spectrum. Only change is an increase in intensity of the "nebular" lines - HII, OI etc. - that seem to become more pronounced as the magnitude drops - and then fade a little as the thing rebrightens.

I'm trying to get an hour or so timeseries in V of it this morning.

[Merlin66]

Lookin' good!
Well done.
I'd need to add a red sorting filter to accurately record data above 7800A.

[Merlin66]

Wall to wall cloud last night - hopefully better tonight.....
Has any else got some data?

[Terry B]

Yes I did
Data from last night
V= 4.937
B = 5.028
This is a slight drom in V and less of a drop in B since my last measurement on 5/1/14
The spectra shows an identical relative Ha emission but an increas in the blue continuum.
When I graph the flux calibrated data, there has been a drop in the absolute height of Ha but an increas in the blue continuum. This fits with the reduction of B-V my photometry displays.
Cheers
Terry

[Merlin66]

Well done Terry!
I'm pleasantly surprised to see the magnitude holding up.....
Your data will be well received.

[Jon]

Good stuff Terry.

The previous night (Friday) I had V 4.95 and B 5.04.

Looking at the spectra overall for this nova there's an interesting fluctuation in the level of the blue continuum. I at first thought I was being sloppy with the instrument response correction, but I'm sure it's real. I'm not quite sure how it lines up against the magnitude fluctuations.

Seems to be a fluctuation in how much "fireball" we see vs how much extended and increasingly nebulous ejecta.

[Terry B]

I agree Jon.
I was worried that there was something wrong with my instrument response but I checked it carefully using various processing methods. I kept coming up with the same response so I ageee that it seems to be real.
It will be much easier in a month when it rises at a better time.
Terry

[Jon]

Here's mine of tonight. Shows the slope to the blue we were talking about.

Also, the NA line at 5890 is looking different. I'd be interested to see what the higher-res spectra of this look like.

[Merlin66]

Still cloud down here last night....

[Rob_K]

Hi all - I actually got up early this morning rather than staying up late and the sky was absolutely brilliant! First time I've been really dark adapted for this nova since early Dec and it was still a little gem naked-eye, amazing! Then I turned the camera on and that bit was over sadly...

Anyway, first time I've taken a spectrum of it since 6 Jan (why bother when you guys are on a roll!) but I notice some big changes since then. Most obvious is the continued growth in strength of the H-gamma line. I now have a long series of low-res spectra of this nova and when I first started shooting the violet end of the spectrum was barely registering and the H-gamma line was invisible or barely visible.

Second is the deepening of the hydrogen absorption lines (P-Cyg profile).

Last night's spectrum is on top, 6th below. Taken with SA100 grating, both sets with Canon 650D, 200mm lens, 12-sec exposures, same ISO & F/stop.

EDIT: had to reduce file size to upload and I notice a bit of jpeg compression - better version here (if PBucket doesn't let me down!): http://i727.photobucket.com/albums/ww271/Rob_Kau/NCen201306-12Jan2013spectrumtext.jpg


Cheers -

[Jon]

Nice, Rob. That's now three of us who have recorded the brightening of the blue end of the spectrum.

I have had the opposite experience to you - this is the first spectrum I stayed up for, as opposed to setting the 3am alarm (which my wife has attempted to veto). A bit less detail because airmass was about 2.2 when I took this.

Still, more civilised :-)

Oops, just realised the title on the image is wrong. It's 12/1/2013 13:30

[Rob_K]

Nice work Jon! I notice little 'steps' that appear to exist between the H-alpha and H-beta absorption and emission lines. Any handle on what they mean, if anything?

Cheers -

[Merlin66]

Managed to collect some data around Ha and Hb.
The P-Cyg profiles have changed (evidence of a third dip???)
and the Fe lines are getting "untidy"
I'll upload ASAP.

[Merlin66]

The attached profiles around Ha and Hb show some interesting features - there appears to be the start of absorption in the lines, and the P-Cyg is getting more complex.

[Rob_K]

Excellent Ken! Clearly shows the little 'steps' between the absorption & emission lines.

Cheers -

[Merlin66]

Rob,
You did well to pick that level of detail!
I've cut your jpg, converted to Luminence and exported to VSpec.
The attached profile (roughly calibrated) shows what's there.....
(We can get a better result from a cropped RAW ;-) )

[Rob_K]

Thanks Ken - yes, I have RAWs, I've just got to get around to forwarding them! There is a small computer issue that's been holding me back, although in truth that's probably just an excuse! My old version of PS won't handle RAWs and my desktop's disc-drive has ceased to function as far as loading camera software goes. I was going to do it on the laptop but blah, blah, blah... ;) :lol:

:thumbsup:

Cheers -

[malclocke]

Fantastic Ken.

Showing a further increase in velocity of the absorption features. I'm not sure if it's the same phenomenon, but a very similar progression is shown in Steve Shore's 'Spectroscopy of Novae - A Users Manual', Figures 4 and 5 (pages 8 & 9) http://arxiv.org/abs/1211.3176

Unfortunately I can't pretend to be able to decipher the accompanying text.

[Merlin66]

I've uploaded my "backlog" of files to Francois.....
Let's see if we can get Steve interested....
I'll send him an email.

[Jon]

It does have moments of complete incomprehensibility to those of us who haven't got all the quantum energy state transitions, along with accompanying resonances (whatever they are) committed to memory!

[malclocke]

I think a resonance transition is just when a photon of a particular frequency is absorbed and then one of the same frequency is emitted as the electron drops back down to it's previous energy level.

[Jon]

Ah, is that all? That's simple enough. When he writes something like "During the cooling stage, when the optical spectrum is strengthening, the ultraviolet – the site of the resonance transitions of the same iron peak ions that dominate the optical spectrum – suddenly becomes optically thick" I thought there was some obscure quantum relationship between UV iron ions and the FeII we are seeing in the visual.

But now I reread it, all he means is that in the UV, the Fe is being bombarded by UV wavelengths, so absorbing and re-emitting individual photons (resonance) at those same wavelengths. But up in the optical spectrum (e.g. at 5018 and similar) those same ions are emitting photons through recombination, as they absorb an electron and emit a photon and move from FeII to FeI), or through transition, as they lose a photon as they drop down an energy state.

That makes sense, as the wavelengths being pumped out by the WD are strongest at the high-energy wavelengths, UV and lower, yes?

Thanks Malc, another piece falls into place.

[Chochawker]

Numerous celestial bodies managed to align themselves for me two nights ago and I got a second look at the nova.

Timing meant I wasn't able to get up early, and I was playing with a new camera, but at the end of the session I decided to see what could be recorded.

Because it wasn't planned and involves a different camera, I've ended up with 15 Angstroms per pixel instead of the usual 9.5-9.7.

Anyway, excuses aside, this was 10:40 pm Sydney time on 14th January.

Most of the features seem to line up quite well with Jon's spectrum and as a result I've taken his identification.

I've also included a comparison with my earlier spectrum.

[Merlin66]

Good to see more data being collected.
The red response looks a bit strange...could be 2nd order contamination or camera response.
Which camera and set-up did you use?

[Chochawker]

Both sets are with a 10" newtonian and SA100.

Up until now I've been using a DMK41, and the first result is with that camera.

The most recent is with an Atik 383 (mono).

It would be a pleasant result if it was only the red end that is rubbish. :lol:

[Terry B]

Very good. That must have been quite low to the horizon at that time.
Terry

[Merlin66]

No imaging in the past couple of night, and probably tonight also - the over night temperatures were above 34 deg!!
I hope between us we can keep the data flowing....

[Chochawker]

Thanks.

Yes, I'm fortunate to have a clear view down to almost 0 degrees from the east through to the south. The down side is that view includes Sydney Olympic Park and lots of other sources of light.

Nothing possible from me until weekend, if weather permits.

If possible, I'll try to collect data with both cameras, and get a better grating-camera distance for the Atik.

[Jon]

Got one last night. The previous nights were crazy - even though in Canberra the overnight temperature aren't as high as you guys at the coast. I had a crack at some imaging on previous nights, but the thermal noise in the (uncooled) guide camera caused the scope to jump all over the place.

[Chochawker]

I had another go with the Atik 383 last night.

I'm still sorting out a reasonable way of getting a decent grating-sensor distance and have gone from 15 angstroms/pixel down to 7 as a result.

I think the problem in the previous spectrum was due to the way I had determined the instrument response.

This version is still not great, but I think it is less wrong than the previous attempt.

10:30 pm Sydney time on 18th January.

[Jon]

Looking good, Malcolm. I thought there may have been an instrument response issue in the previous ones.

This one is good on the correction front. I think you are setting yourself a big task going for it at 10.30pm. You are operating at well over 3 airmass. The thing about the SA 100, without a slit, is that resolution is determined by the size of the star image, and that low, it's going to be a smear.

I've been quite happy with the SA100 results I'm getting recently, but I was definitely getting tighter results when I was getting up at 3am when the nove was at airmass 1.4 or so, spending 20 mins focusing (that's right. It makes ALL the difference). Now I'm getting lazy, grabbing a spectrum at midnight before I go to bed, but I should really wait till it's higher in the sky.

I think you'll find that accounts for the difference in resolution of your last spectrum compared to your very first - which was remarkably good.

Re spacing - I also have the Atik 383L+. I find using it on the front of one of these (http://astrograph.net/Baader-Variable-T2-Extension-29-46mm) gets me 9.0 A/pixel which is just perfect. The adapter came with my 383.

Cheers

Jonathan

[Chochawker]

Thanks for the comments.

Next chance I get I should hopefully be able to get the correct spacing.

Yes, it is very low in the evening, unfortunately I'm not having much luck when it comes to a clear sky on a morning when I can be up at 3.

Do you have any tips or tricks regarding focus?

So far I have been concentrating on a given feature (in this case the Halpha line) and attempt to get it as narrow as possible based on what I see on the computer screen.

Of course this is much harder when it is lower in the sky.

[Jon]

:-) The good news is, at the rate it's fading, this nova will still be bright when we can record it at a civilized hour.



Yes, it certainly is. That's what I do - although I find it easier to keep my attention on the darker absorption lines. One of the things I had to do with focusing is simply to slow down. I was hitting the "Expose" button for the next focusing image while the assembly was still vibrating from my last focus adjustment, even though I was using a USB-controlled electric focuser. Making myself count to five before the next one worked wonders :-)

[Terry B]

A agree with you guys about not getting up at 3am. I don't like it at all.
I'm located further north so it is lower for me but I tried at midnight last night when it had an airmass of 3.1
This just clears the trees to my south at that time. It will get easier in a month or so.
My spectra seem ok but my photometry was crap with an error of 0.15 on V. FWIW I measured V = 5.50 and B = 5.51
The nova has strengthened in Ha in the last week in both absolute and relative terms.
Terry

[Jon]

Interesting spectra, Terry. You can just make out the double P Cygni absorption lines in Hb and Hg. Also, that shifting of the continuum to be stronger in the blue has dropped off a bit - the changes in B-V seem to be driven by this.

Airmass of 3.1 will make photmetry a pain in the neck :-). But I guess with a slit spectrograph you won't get the same resolution issues as we SA100 users at high airmass.