First Light with RH200

[avandonk]

The Lodestar guider I ordered did not turn up today as expected. So this image was done unguided.

10x120s with 3nm HA, 10x120s with 3nm NII and only ten darks. No flats etc.

I assigned the NII to red and the HA to green. There is a bit of variation between the two but nothing obvious.

The adapter Luke made for means the light path is not vignetted at all by the image train.

Only guided images will show what is really happening in the corners. So far it looks pretty good in spite of the processing.

Large full resolution image here 12MB

http://d1355990.i49.quadrahosting.com.au/2012_04/car_NII&HA.jpg


Bert

[Mighty_oz]

Have to agree with u lots of potential there, maybe 90 sec subs, seems u got a bit of trailing there as well as focus is not quite there ? Seems u don't have the detail i'd expect from such a large scope compaired to my fsq. This on the PMX yeah ?
Anyways, once u get it all together you'll blow us all away with your images :)

[ballaratdragons]

WOW! Full res image shows nice round stars in all 4 corners :thumbsup:

Niiiiiiice :)

[avandonk]

Here is an RGB of Omega Cent. 10x60s for each of RGB. 30 min total.

Flats are needed here.

Large image 5MB

http://d1355990.i49.quadrahosting.com.au/2012_04/OC_col_60s_L_10.jpg


Bert

[Paul Haese]

Welcome to multi filter processing Bert. Quite a lot of potential. I don't agree about the round stars in the corners. Plenty of tilt and stacking rotation and maybe polar alignment issues yet. You will sort this in time anyway. Once you get guiding you will know for certain what issues are present.

With processing I suggest you get hold of a copy of CCDstack. Very good program for calibration, stacking and combining. Then use something like PS for final processing.

Looks forward to more.

[TrevorW]

Plenty of potential as shown in the image of Omega (full),

[avandonk]

Considering the mount has not been aligned with the RH200 and thus polar alignment is not quite right and no guiding and no flats and rushed rough and ready processing with a paucity of data drawing any conclusions would be premature evaluation. Even focus was just by eye and not by any definitive objective method, Cloud interrupted anything more substantial.

Conversely considering the conditions this system is a real goer. It just needs some dedicated tweaking. I have not even started collimating and aligning the optical axis with the imaging train. It has all just been bolted together without any fine adjusting.

Here is the OC data cleaned up with GradientXterminator 15MB

http://d1355990.i49.quadrahosting.com.au/2012_04/OC_col_60s_L2_GX2_12.jpg

And a quick NGC 6357 20 min HA. ie 10x2 min. Remember this is 3nm NB at F3 with NO flat correction!


Bert

[avandonk]

Here is a little 5MB animated gif of the same area in glorious 'HA' with the RH200 and Mike Sidonios and Peter Wards scopes which have nearly twice the focal length and 12" of aperture and nearly as fast at F3.8. Mine is the yellow one. A comparison at 4.8 degrees out at the corner of the field of my optic was not possible.


http://d1355990.i49.quadrahosting.com.au/2012_04/HAcomp.gif


Remember mine is unguided and not 'deep' yet but their images may suffer from jpg compression.

Bert

[Peter.M]

Jesus, when you say first light you dont muck around. This scope is going to be a monster when you get it singing. I look forward to seeing the results.

[tilbrook@rbe.ne]

Wow!!:eyepop:
Can't wait to see some of these images in comlete form.
Tried to load your 5 Meg image, but gave up as I'm on mobile slow band!

Cheers,

Justin.

[multiweb]

Looking good Bert. Enjoy the new toy. :thumbsup:

[avandonk]

It will sing and the song will be our lust for understanding!

Bert

[avandonk]

By the way I intend to control the whole optical systems temperature within about 0.2 C. This will mean focus will be constant no matter what the ambient temperature does. The Astrodon filters were very expensive but they essentially do not vary as far as optical path is concerned. Time will tell.

It is all about careful control, too much and you end up with oscillating systems. Too little and you do not know where you are!

When I am at a séance I always like to strike a happy medium!

Bert

[gregbradley]

Very impressive first images Bert. These are better than I expected. No real evidence of coma even though your chip is larger than the specified corrected circle of the scope.

Bottom left shows slight tilt and top right shows something similar but almost slightly coma. I'd say your getting a small amount of tilt (it may be only .15mm tilt here to get it in perspective).

I've seen similar tilt issues on other scopes and its only a small amount of tilt. It doesn't take much with that large chip.

Further polar alignment and autoguiding will take care of the guide errors. A few runs through T-point will get it singing.

I recently redid my T-point model and refined polar alignment on my PME and CDK17. Now I get objects in the middle of the chip on go-tos and round stars at 20 minute sub exposures at 3 metres focal length.

These SB mounts are awesome.

T-Point is an amazing tool and well worth the learning curve. Sky X T-point is even better as it has the super model function.

You're on to a winner here Bert.

Keeping temperature stable is a smart move. How are you going to do that?

I think ideally the scope mirrors are a tad cooler than ambient. Hotter is bad for sharpness. At F3 it may not be as noticeable but at long focal length it is definitely noticeable. I turn the fans on my CDK17 on a few hours before I use it. I need to get the mirror .5C or less to ambient to get sharp focus. If the difference is .1C it starts looking a little bit soft.

I'd like to hear how your Lodestar goes. I am using one but I have an SBIG STi on its way to me. Main problem for me with Lodestar is CCDSoft does not seem to do library dark subtract when autoguiding. I either use autodark (and that subtracts half the star unless its moved enough) or none if the guide star is bright enough.

I found my Lodestars have had artifacts . A horizontal white line plagued it and affected guiding (auto select guide star would pick an artifact over a real star). This artifact disappeared when using 64bit driver on my Win 7 laptop. But 2nd Lodestar has a white line down left side and it is sometimes selected over the star. You can tell when it has as guide errors go up to 15 pixels! I simply use autodark when this happens. I get slightly worse guiding performance using autodark (there is no shutter so it can't do an accurate autodark and subtracts part of the star as well).

Lodestar is designed to be used with PHD so perhaps all this goes away with PHD - I've never tried it. ST402ME is the best autoguiding camera but a bit heavy, plus 2 cables - power and USB. Its super sensitive and cooled so very little noise and no autodarks required. Plugs on mine were a bit unreliable though. Back to service it goes.

Greg.

[avandonk]

To keep temperature of the optic constant is very simple, a bunch of dew heaters controlled by a PID. The distribution is a gut feeling but a careful analysis of temperature distribution by measurement is a must.

OK the dew shield should be just above ambient to radiate the equivalent heat loss to the cold sky to the front optic. It is not about having a nice warm optic! It is all about an optic that is in equilibrium with it's environment.

It is my understanding that a sealed optic at a constant temperatue has no temperature gradients. Hence no convection or conduction inside to stuff up the light paths.

I can show you how all of this works.

Bert

[gregbradley]

Sounds good Bert. I know Roland Christen goes to great lengths to control convection currents in his scopes as does the planetary imager Bird.

You should get a gain from that but being a widefield scope it may not be as noticeable as if it were 2-3 metres in focal length.

It all adds up though.

I sometimes have a heater on under my computer desk at my dark site and wonder if it will affect images. I haven't noticed any effect. Its not under the lens of course but sometimes it is looking near the plume.

The theory being comfort of the imager is senior to any slight loss of sharpness!!

Greg.

[avandonk]

Greg Luke Belleni and I are about to design a cradle to hold the focuser filter wheel and camera in situ and just slide the whole lot back and then we have access to the collimation and optical path alignment adjusters on the back of the RH200.

Your analysis is most probably correct. Easy adjustment is the goal.

We are only just starting!

Bert

[gregbradley]

That sounds good. Have fun with it.

I used simple spark plug gap gauges from SuperCheap Auto (about $6).

You can then use those to shim one side. Then again you have an adjustable tilt adapter.

You can adjust it and then do a 10 second focus shot with luminance filter at 1x1 binning and look at the corners.

It can be done very quickly that way. 1x1 shows up all the warts.

Greg.

[Luke Bellani]

Really great images Bert.
It looks you got the focus issue beat too.
Another clear night tonight so get out there :)
Cheers,
Luke

[Paul Haese]

Me too Greg, peltier cooled C14 to control tube currents and bring optics to thermal stability. :)

[LucasB]

The initial test shots are very promising. The tinkering will well be worth it!
Lucas

[strongmanmike]

Yeh I agree, considering it is early days, these results are right on track for sure :thumbsup::thumbsup:

Great field of view huh? ;)

As for your comparison with the AG12 and RHA though, not sure it was all that revealing, animated giffs of jpeg compressed images are always lower res.

Here's that same area at full resolution (http://www.pbase.com/strongmanmike2002/image/142686335/original) from the AG12 (complete with details inside Eta herself ;) )

Looking forward to more :thumbsup:

Mike

[Peter Ward]

Agreed... compression artifacts are hiding a whole bunch of data there Bert.

My own (roll-over) comparison showed the AP RHA had stars that were about 30% tighter than an AG12 (using data via Mike's post above)

....but it was and apples and oranges: i.e. meaningless.

Mike's 100% data was decidedly deeper....which will bloat stars in the same instrument, let alone comparing it to a third party with different seeing, focus and who knows what else.

Anyway...Good luck with the scope Bert...I'm sure it will deliver some excellent Wide Field results.:thumbsup:

[strongmanmike]

That's very interesting Peter, I'd like to see the 100% RHA data for the above field along side the 100% AG12 data actually and not as a roll over though and neither coregistered ie warped by software either, just cropped as close as possible to the same field...I'm intrigued :confuse3:

Mike

[Peter Ward]

Sorry, already did a rollover... but I didn't knowingly warp any data...just registered an up-scaled crop by 200% for my own curiosity...

Resulted in big, non-web friendly files, hence the roll-over response is not instant.

Here is the link (http://www.atscope.com.au/BRO/roll/RHAAG12.html)

I frankly couldn't glean much, as the RHA data is quite short, with zippo processing other than scaling.

I can see layered masks and all sorts of other processing in the AG12 image.... hence my comments on the link above. i.e. I think the comparsion has no quantitative value.

[strongmanmike]

Hmm? ya can't really do it like that, which ever one was coregistered will be blurred, you need to take the plain non coregistered just 100% res (not upscaled) jpeg data from the two scopes and place them side by side, once you upscale and coregister etc it introduces all sorts of issues....

Mike

[Peter Ward]

Sorry, that makes no sense to me.

Either way, the transformation is linear with stacking (ie rollover) or side by side presentation. All you are doing with a rollover of same-scaled data translating it, from side-by-side to upper-lower.

An up-scale (2x) transform is also linear....and simply makes a 3mm stellar footprint look like a 6mm one.

Having pictures side-by-side or on-top of each other doesn't change the intrinsic data.

[strongmanmike]

I think it does, if you coregister one image to the other the one co registered will be warped to match the base image and this blurs the data a little, plus why the 200% upscale anyway?

[Peter Ward]

Linear Algebra 101. If what you suggest is true then RGB combining or stacking of multiple images is doomed to fail with anything less than perfectly aligned raw data (mine sure as heck isn't)

The 200% upscale was simply so I could see foot-print changes better...the relativities stay the same.

In any event Mike, it's a silly comparsion...(sorry Bert) as they are simply too many variables (seeing, filter homogeniety & figure, data depth, processing etc. etc. ) to draw any meaningful conclusions.

[strongmanmike]

:rolleyes:

You like dragging my images into comparisons don't you Peter...I'm flattered that you take such close notice :)

[Peter Ward]

I often compare FWHM's from many different (web) images... so no need to fret, your work is just one of many sources I use to sus-out how various instruments may perform.

Plus, Bert started the process... and you asked for something (similar) that I would not have otherwise posted.