Nova Del 2013

[Terry B]

Dear all
A very bright nova has been discovered in Del.
http://www.cbat.eps.harvard.edu/unconf/followups/J20233073+2046041.html
It is very bright at around V mag 5. I took images and spectra of it tonight.
I was limited to 4 sec exposures with a V filter as it saturated with a longer exposure.
The spectra is taken with my LISA spectrograph. This satureated with exposures longer than 45 sec.
This is the brightest nova in quite a few years and will be interesting to follow as it changes.

Terry

[Jon]

I clearly picked a good week to start dabbling with spectra :-)

As a complete newbie I feel a bit embarrassed following on Terry's marvelous spectrum, but I also got something with my SA100 tonight.

Now, everyone seems to be saying that it is "clearly a Fe Nova". I'm about to embark on some self-education, but what is it about the spectrum that leads to this deduction? Forgive my ignorance, but I guess this is a good place to ask.

(I should point out that these are actually the first emission lines I have ever captured for myself. I'm quite excited)

[BTW, thanks for the tips from everyone and especially Ken in the other thread. I seem to have my head around focus, calibration and instrument correction now. At least, I'm getting results that look a bit meaningful]

[Merlin66]

Paulo published the following, which will be of interest:

ATEL #5282 reports Nova Del 2013 is a classical nova in the early fireball stage:
http://www.astronomerstelegram.org/?read=5282

I report here a couple of documents for novae:

In appendix (Table A1) of paper "Origin of the ‘He/N’ and ‘Fe II’ Spectral Classes of Novae" (R. Williams) there is a finding list for optical emission lines
http://arxiv.org/pdf/1208.0380.pdf

A reference document by S. N. Shore, Spectroscopy of Novae – A User’s Manual
http://arxiv.org/pdf/1211.3176.pdf

[Merlin66]

Terry,
A great catch there!
Well done!

[Terry B]

Lots of good info about novas here.
http://translate.google.com.au/translate?sl=auto&tl=en&prev=_t&hl=en&ie=UTF-8&u=http://www.astronomie-amateur.fr/Projets%2520Spectro4%2520Novae.html&act=url

Terry

[Rob_K]

Excellent work once again Terry! :thumbsup:

I was going to concentrate on getting a spectrum with the Star Analyser last night but incoming weather meant I had to try too early and the area never fully cleared the trees at my place. I didn't have any charts and although I had a pretty good idea where the nova was I could never see enough sky in narrow gaps in the trees to pin it down! :rolleyes:

In an attempt to get something (anything!) I resorted to shooting the gaps from various angles using a wide 55mm zoom and as luck would have it I did get the nova in a number of frames. Rough and poorly exposed though. I did a little stack of 6 barely-usable frames but it's got me a little confused. I would have expected to see at least a bright H-alpha line but the spectrum appears featureless (ignore the lines, just noise).

I've attached a composite image, top is a crop from a late frame showing the nova and its spectrum (as well as the spectra of the main Delphinus stars) and at the bottom bar spectra of the nova, and T Pyx for reference.

Any comments or advice as to why I mightn't have picked up the hydrogen emissions? Thanks. :thumbsup:

Edit: the bar spectra aren't exactly the same scale - I just roughly matched the colours as they were shot at different scales. OK for the purposes of the exercise though...

Cheers -

[Merlin66]

Rob,
Good catch under the circumstances...
If you check out some of the other SA100 shots on the forum you'll see that when the resolution is low the Ha peak is not very evident....
If you can get around 8A/pix dispersion and a good exposure the emission lines should show....
(He says roping down the observatory roof from the hi-wind and rain coming...)

[Rob_K]

Thanks Ken, that's pretty much what I suspected. :thumbsup: Awful spell of weather isn't it?

Cheers -

[Jon]

The spectrum I posted above, straight after Terry's, was taken with the Star Analyser 100. 8.8A/pixel. Both the alpha and beta emission lines are pretty clear :-) It's a single 2-sec sub. I've now got a much less noisy one that is a stack of 6 subs with darks and bias.

[Terry B]

A follow up tonight. There has been a big change over the 3 days.
Cheers

Terry

[Terry B]

The spectra is still rapidly changing.
http://i566.photobucket.com/albums/ss109/TCB168/NovaDel18_19_8TB_zps8c7c79ad.png

[Jon]

For what it's worth, here are two spectra I got with the SA100 on 15 and 18 August (as it happens, the date on which the Balmer emission lines had dropped to their lowest levels before brightening again)

[Terry B]

I got my name on another Astronomers Telegram.:thumbsup:
www.astronomerstelegram.org/?read=5312

Terry

[malclocke]

Well done Terry, I think you can expect to be seeing your name in a published paper from this one too.

In case anyone here isn't following it there is a thread at http://www.spectro-aras.com/forum/viewtopic.php?f=5&t=682&p=2703#p2703 where Terry and others in Europe (why is spectroscopy so popular in France?) are posting their results. I've been having to enjoy the nova vicariously as I've been under almost continuous cloud since the outburst :( Hoping to get my SA100 on it before it fades out, fingers crossed.

Malc

[rmuhlack]

This is definitely a good month to begin a journey into astronomical spectroscopy!

I used my new SA100 for the first time last night. The SA100 was screwed onto the 1.25" nosepiece of my QHY5 with spectra processing using a trial copy of RSpec. The scope used was a Long Perng 80mm f6 achromat.

After having taken a test image with my 400D to confirm the location of Nova Del 2013, I calibrated first on Fomulhaut, then centred on Nova Del 2013. I had to swap out the QHY5 between Fomulhaut and Nova Del so that I could centre the new target. I found Nova Del much harder to focus on than Fomulhaut, but hopefully I can finetune the workflow so that I dont need to change cameras and refocus everytime I change targets.

Anyway here it is. Angstroms/Pixel = 12.2

[malclocke]

Good work Richard!

I too am getting acquainted with my new SA100, and finally managed to get a very dodgy spectra of the nova last night. Also using a QHY5 but with a 10" dob. I'm having to do 'drift' spectra, and the nova is pretty much at the lower limit of magnitude to do this with my setup I think. Almost no signal from the continuum, but the emission lines were easily visible, it was obvious I had the right target in the live view.

My efforts are attached and should provide a suitably low bar for everybody else to feel better about their results ;)

Malc

[Merlin66]

Richard,
A couple of comments..
Can you add a flip mirror in front of the camera? Makes it much easier to aquire the target.
( I can use GOTO and CdC with the NEQ6pro to just "drop" the target onto the grating....)
It's standard to present the spectra with the zero order to the left - this gives a spetrum orientated with blue to the left and red to the right - usually needed when you start to do calibrations...
Good start.
Well done.

[rmuhlack]

Thanks Ken. Glad to hear I'm on the right track!

A flip-mirror is a great idea - I will need to add that to the shopping list. If I had used my normal setup procedure I would be able to "drop" targets onto the sensor as well (especially at only 480mm FL), however it was a last minute decision to set up the second mount for spectroscopy (I dont have a permanent setup) and so I didn't finesse the polar alignment / GOTO model.

Re the spectra I posted before, I had the zero order to the left and had calibrated on an A-type star. I had just cropped the curve. I have now gone back and selected frames with better FWHM for calibration and presentation. Hydrogen Balmer lines are also shown for reference.

[rmuhlack]

btw I was wondering about attaching the 1.25" nosepiece with the SA100 to a T-ring with my full spectrum modded 400D (which has both UVIR and anti-alias filters removed) - I suspect that this camera has a wider spectral response than the QHY5, as well as having a wider FOV, less noise, 12 bit ADC, and the ability to capture longer exposures.

However using the RSpec calculator (http://www.rspec-astro.com/calculator/) it tells me that my resolution will be 7A/pixel with this setup. Is this too small? The two scopes I would be using are a Vixen VC200L at f9, or a 80mm f6 refractor

[Merlin66]

With an f5 system, there seems to be a "sweet spot" around 8-10A/pixel.
Going <8 A/pixel is like "empty magnification" - makes the spectrum larger but with no improvement in resolution.
You should also aim to have the spectrum horizontal across the chip. This reduces the likelyhood of introducing artifacts during the processing.
Onwards and Upwards.

[Terry B]

The nova continues to evolve.
Attached is an image from last night 2/9/13 compared to 30/8/13.
The hydrogen lines are now very strong and continue to strengthen.
I have also attached a comparison of the first image I took on 15/8/13 compared to last night. You would almost think they are different stars as the spectrum has completely changed with the evolution of the nova.
I have expanded the y axis to show the earlier spectra more clearly but the Ha intensity goes up to 45 for last night spectra.
Cheers

Terry

[Rob_K]

Great work Terry! By the way, congratulations on co-authorship of "Discovery of Pulsating Components in Southern Eclipsing Binary Systems". :thumbsup:
http://www.aavso.org/sites/default/files/jaavso/ej241.pdf

Cheers -

[Terry B]

I've made a couple of animations of the change in the spectra of this nova.

Cheers
Terry
http://i566.photobucket.com/albums/ss109/TCB168/NovaDelanimation_zps44f48b3a.gif
http://i566.photobucket.com/albums/ss109/TCB168/Novadelanimationfullres_zps2047a7a2 .gif

[Merlin66]

Terry,
Very nice!
A great way of showing the dramatic development of the nova spectrum.
Well done!
(And they say spectroscopy is boring!!)

[Jon]

My DSLR has been off for repairs, and I'm patiently waiting for the arrival of my L200 (not for a few months as JTW Astronomy is moving, it seems). Then a rather nice tax return cheque arrived, so I managed to pick up an Atik 383 L+.

Last night was the first chance I have had to put the SA100 in the filter wheel. The distance from the sensor was on the small side - only got 17 A/pix. I'll sort something out to get it closer to 8-9. But nice to see the O I lines up in the IR part of the spectrum for the first time.

Can't wait for the L2001

[RobF]

Thanks Terry. Really enjoyed those.
Great way of highlighting nova activity.

[Jon]

+1. Really interesting way to see the dynamics.

[Jon]

My new Atik has a fault and has had to go back ... Grrr ... so it's back to the DSLR. Nevertheless, mazing how much detail you can get with the SA100 and a DSLR. Apart from the H lines (hard to miss!) there's He I, NIII, and the forbidden [NII] and [OI] lines.

[Jon]

Here's a spectrum of Nova Del 2013 which I took with a SA100, 10" SCT, and a Cannon EOS 60Da. c.6 A/Pix dispersion, with the grating about 50-60mm in front of the sensor. I was pleased how many emission lines were detectable with this setup - not to mention how easy the spectrum was to annotate with RSpec :-)

[Merlin66]

Well done!
Good results from what is now a faint object!
(I think the peak at 5000A may be due to the increasing [OIII] @ 5007A - shows well on Terry's LISA spectrum of the same date.)

[Jon]

Thanks Ken. I've corrected that annotation. I've been reading Steve Shore's notes on this with great interest, but I'm still in need of a "Nova spectroscopy primer" - a blow-by-blow account of the stages in the evolution of a nova and the spectroscopic features you'd expect to observe. I understand some of the evolution of the Hydrogen lines, the P Cygni profile, and the He flash, but as to why we are seeing OIII not N now, what is supposed to be happening soon with Fe, and so on - I'd love a dummies' guide!

I'm having fun with the SA100. Can't wait for my L200 to roll off the production line in Holland, though :-)

[Merlin66]

Although somewhat dated, the "Bible" is Cecilia Payne-Gaposchkin's "The Galactic Novae"
Well worth searching for a copy!

[Jon]

Thanks Ken. Just found a free online copy at https://archive.org/details/TheGalacticNovae

[Terry B]

Very good.
For comparison is my spectra taken on the same night. It has been flux corrected hence the very small numbers on the vertical axis.
The features you describe are present.
Terry

[Jon]

Nice one Terry. I've been finding your spectra of the Nova over on the Astronomical Spectroscopy forum (http://groups.yahoo.com/neo/groups/astronomical_spectroscopy/info) incredibly useful for understanding what's going on.

Forgive a newbie's question but it seems to me that getting all of the continuum from 4000-7200 into one image on a 314+ sensor at R=1200 is really impressive. Other spectra seem to capture far less at that resolution. How do you do it?

One of the reasons I'm asking is because I've been trying to work out which gratings to order with my L200. I want at least one to capture as much of the continuum as possible but think I have to go down to R=300 or even R=150 to do so. Am I missing something?

Cheers

Jonathan

[Merlin66]

Jon,
The answer lies in SimSpecV4 (in the astronomical spectroscopy files area + explanatory notes)
It all comes down to collimator/ imaging focal lengths, the l/mm of the grating and the camera pixel/ chip width
Terry uses a LISA which has a 130mm collimator, a fixed 300 l/mm grating and a 88mm imaging lens.

( I use an 80mm collimator/ 300 l/mm/ 50mm imager in the MG80 concept - full spectrum coverage lo res)

EDIT: The spreadsheet for the Spectra-L200 attached - a 150 l/mm grating will give a coverage of 4000- 7000A at R=500.

[Terry B]

The R figure is worked out by the processing software based on the FWHM of the neon lines in the calibration spectra as well as pixel size etc. It varies between 800 and 1500 depending on how I do the neon calibration. The actual range on the CCD is determined by the magnification of the spectra and the size of the pixels. I think it is 2.3A/pixel (Im at work so don't have the software infront of me).
For the Atik camera and the LISA this allows a spectra to range from 3800-7300 across the frame. It was much larger when I used my SBIG ST8 as it has a bigger chip but lower resolution due to it having bigger pixels.
The L200 is a different design and suffers more with field curvature making the ends of the spectra out of focus. This limits the practical width of the spectra. I think the L200 is better for medium resolution spectra and not to worry about trying to use it for full width spectra. Regularly changing the grating would be a pest to do and a but risky due to possible damage to the gratings. Drop it once and it is useless.

Terry

[Jon]

Thank you both. Helpful advice.

[Merlin66]

Jon,
Terry has made some good points.
With the Littrow design (both the Spectra-L200 and LhiresIII) the collimating/ imaging achromat is a longer focal length (200mm) and has a "sweet spot" of about 10mm diameter.
In other designs - MG80/ FC120/ Classical etc you can alter the collimator ( even use a mirror!) and use photographic quality imaging lenses which give better wide field coverage.

The latest design of the Spectra-L200 only requires loosening three thumbscrews to remove and replace the grating assembly, but as Terry says, if you drop it you're toast.

[Jon]

Good - I think I'm following all that, which means my understanding of spectroscope design is improving.


That I didn't know. I thought the exchangeable gratings were a interesting feature of the L200. But I guess that's just another of a fairly long list of astronomical equipment in the "drop it and you're toast" category. I'm not thinking of playing basketball with my CCD camera, my focal reducer, my eyepieces or my laptop, either ;)

But seriously, I wasn't aware that gratings were particularly more sensitive than other optical components. Good to know.

I wonder if there's any news on how the L200 run is going at JTW Astronomy?

[Merlin66]

Jon,
Unfortunately reflective gratings are ultra sensitive...they can NOT be cleaned...dust, moist breath, fingerprints all spell disaster for a grating.
I keep mine in sealed Tupperware containers when not in the spectroscope.

There have been some delays with the CNC machined components for the new slit/guider...but I believe they have now been overcome.