M31 with Televue/FLI prototype imaging system

[Paramount]

Hi
As the moon wasn't present I thought I'd have a go at some LRGB and I was able to complete M31 in three nights with some cloud interruption in between. M31 just about clears the roof of my house so I am able to image it as soon as it gets dark. This was taken with the Televue/FLI prototype imaging system that I am testing at the moment which consists of a NP127is (without the mechanical manual focuser), a custom built spacer tube with built in adjustable tilt and focusable field flattener, this is attached via zero tilt adapters to an Atlas focuser, Centerline filter wheel and Pl16803 camera. (details on the system can be seen on my previous post of the veil nebula).
Exposure times were
26x10 minutes Luminance
12x10 minutes Red
8x10 minutes Green
11x10 minutes Blue
Auto guiding was by a Officina Stellare Falco guide scope and SX Lodestar with dithering.
The system is proving to be very easy to use and the focus is very stable with only one adjustment necessary during the night.
Due to light pollution there were varying gradients on the different master frames so I dealt with the gradients before colour combining.
I am particularly pleased with the result as I've managed to pull some detail out of the dust lanes in M110 which can be seen better in the full size version at the following link
http://ic2.pbase.com/o9/29/869929/1/152178687.rUPLmrzo.M31LRGBfinal.jpg
Depending on time and weather I may add some Ha to this but I have heard varying tales as to whether it is worth it with this subject.
When I've a bit more time I will post some pictures of the system on my website
Thanks for looking
Best wishes
Gordon

[Larryp]

Great image, Gordon :thumbsup:

[gregbradley]

Overall a nice image but as a test of a high end refractor imaging system I have to say its disappointing. Coma, fat stars. Its not what you would get from a smaller FSQ106ED. Was the seeing poor? What mount did you use?

The system has a lot of promise though as a lot of people would want a "127mm FSQ".

Greg.

[Paramount]

Not quite sure about the coma reference Greg, I have had a few problems with drift when using a guide scope with my Paramount as I normally use and OAG.
I don't agree with the "fat stars", I don't have particularly good seeing at the best of times where I live with an FWHM that can fluctuate from 1.5 to 3.5 from one minute to the next or worse. Unlike a lot of imagers I don't do any fancy tricks with my stars to keep them "non fat"
Thanks for the comments though, I will feed them back to David at Televue
Best wishes
Gordon

[gregbradley]

Sorry Gordon, my last post was probably pretty harsh so excuse my tone.

Its being picky for sure as it is an excellent image overall. Perhaps coma isn't quite correct as what I was looking at is the stars bottom left seem elongated away from the centre. Perhaps that is tracking/autoguider error/drift. However notice the stars near the corners are not round and odd shaped whereas those in the centre are nice and round - hence the coma comment. Also I notice the stars near the centre of the image are much tighter than those further away. I know its usual for scopes to have smaller spot sizes in the centre than out further. That much different I am not so sure. Yes 3.5 arc min seeing is poor so that has something to do with it for sure. A guide scope may not be the best setup for this scope and a MMOAG would be better as differntial flexure would be distorting the stars that may well be perfect from the optics.

There is also vignetting of the brighter outer stars (the dark tunnel effect). This was a characteristic of the FSQ106N and corrected on the FSQ106ED. I suppose it means a not large enough opening somewhere.

Keep in mind though that excellent scopes already exist so at the price point being considered (TOA130, TEC140, AP130 amongst many others) it doesn't seem to match an AP130 with flatteners at this stage.
The Petsval design in the FSQ is valued for its very flat field. Do you have CCD Inspector? It would be good to see what a plot of the field curvature looks like.

Greg.

[PRejto]

Very nice image, Gordon! I like the colours and detail. I'd be thrilled with such an image.

I do see what Greg is saying, however. Not so much "fat" but something is visible when I zoom in on the full resolution version. The fainter stars show a bit of northerly stretch (if north is up!). I see it all over the image (but only quite zoomed in) so I kind of doubt it's coma that I thnk one might see just towards the corners...so probably it is guiding and hopefully not optical. Still, it seems to be a very nice setup. Is there no way to incorporate OAG into that setup?

Peter

[Peter Ward]

Que? Can't see this myself.

Stars at the top of frame are essentially perfect, though I can see some elongation on the lower edge (may be a slight lack of CCD orthogonality :question: ) but the phrase "being very picky" comes to mind.

Very tidy image just the same :thumbsup:

[LewisM]

I like the image a LOT - great depth to it.

I can see the bloating, but not the coma so much.

VERY 3D float to it!

[PRejto]

Well, you are right! Now I don't see it. I thought I did. Anyway, I put the full sized version in CCDInspector and it does show that the aspect is not as good along the bottom of the frame compared to the top. The overall curve map is odd looking but this is not a fair test given the galaxy takes so much of the field.

Peter

[Paramount]

Hi Guys
Thanks for all the comments, they will be very useful in feeding back to David at Tele Vue. It is very interesting that Peter mentioned that he saw the "star stretch" but when looking again he didn't. I have the same problem on occasions when looking at a computer screen for long periods in that my eyes start playing tricks with me. By the way the orientation of the image is with North to the right which apparently is the classic orientation (who decides this beats me!)
I appreciate what has been mentioned about "fat stars" and "star bloat" but due to the very variable seeing conditions where I live and a FWHM that fluctuates quite a bit between sub frames it is something I'm prepared to live with.
The system isn't designed to work with an OAG due to the inherent problems with the risk of tilt and flexure by adding extra components and adapters into the system and as the system currently stands no extra components can be fitted in because of the focus range and field flattener distances. It is something I will discuss with David from Tele Vue and Greg from FLI.
Thanks again
Best wishes
Gordon

[strongmanmike]

Hmmm? I'm scratching my head...to me this is a very fine image in all respects. Any shortcomings are very minor at best IMO :shrug:.....

A great system I'd say :thumbsup:

Mike

[LewisM]

I agree Mike. I think the nit-picking is merely because of the overall cost of the system and expectations from both manufacturers.

If I could get an image half that good, i'd need to change my undies!

[FlashDrive]

I'm no expert on Astro Images....but that is a great capture.....:thumbsup:

Flash....

[gregbradley]

That's exactly it Lewis. We are talking about a $16K system here not including the camera and filters so nit picking is fair enough. The differences between the high end scopes are relatively minor so its fair to nit pick here.

Its only one image though so its hard to form a judgement.

Greg.

[Paramount]

Hi Greg
Here is a link to the first image I took with this system last month of the veil nebula in HST palette, the post is elsewhere in this forum

http://m7.i.pbase.com/o9/29/869929/1/151820147.oacCNbfO.VeilHSTmax.jpg

Best wishes
Gordon

[RobF]

Nice going Gordon. Wish M31 got that high here!
Gee that veil shot is a beautiful field. 16803 envy!!! :wink2:

[h0ughy]

wow - way over my pay grade ;) nice shot - looks top shelf to me

[gregbradley]

That Veil is a very nice shot. Those very slight star elongations are probably from differential flexure not the scope. You use a PME right?

I use a guide scope on my TEC110 - a Vixen VMC110 I think it is. Its scewed down really hard and on top of a top rail. In 10-15minutes I don't see any star elongation using a PMX. But differential flexure is always a risk when using a guidescope. Have you tried an STi and guide lens kit? It looks pretty solid. I just got one for my CDK when using a reducer as there is no backfocus for a MMOAG. I'll let you know how that goes as it may get rid of that flexure.

Greg.

[multiweb]

Terrific flat field. Dream rig.

[Paul Haese]

The most impressive thing for me is the dust lane in the lower companion galaxy. I have never noticed that before in other images. Great colours too.

[jase]

Too much analysing and not enough appreciation for what is a remarkable scene. Thanks for sharing Gordon. Top marks from me. More please.

[Paramount]

When I first saw the downloads I saw some very faint detail in M110 which I was very surprised at, when I processed it and saw the detail come through more clearly I checked up other close up images of M110 on line and sure enough the dust lanes were there so I was really delighted. I have done this subject a couple of years ago with my FSQED but didn't get the same sort of detail that I am getting now, the extra aperture helps I'm sure, but so far I'm getting higher detail than I have before
Best wishes
Gordon

[Ross G]

What an amazing photo of the most amazing object Gordon.

One of the best I've seen..excellent work!


Ross.

[acropolite]

Beautiful image, have to agree with Paul, the colours and detail are very impressive.