M83

[PRejto]

It has "only" taken 4 months to get this image: weather, equipment problems, equipment misunderstandings and stupidity. Anyway, for what it's worth, here it is.

TEC140, 2X Astro Physics Barlow, ONAG (St-i), Moravian G2-8300, Hutec IDAS

1x1 image scale: .575 arcsec, or ca 1940 mm fl

Guiding has been problematic. I don't know if it is something about the IR signal I'm guiding on, or an issue with my mount, or my lack of experience. Probably all three! I couldn't afford to throw away much data so my not perfect guiding shows. But, some of the distortion may be the barlow/TEC combination.

This image is 4 hours in luminance, and about 2 hours each in RGB (some at 2x2, some at 1x1). I had to crop off the worst bits, and I've downsized the image to around 70%. There are plenty of flaws, but I guess I proved to myself that this could be done. I think I need a camera with better QE to take advantage of this focal length. Collecting luminance was OK, but colour was very difficult!

Thanks for looking, and comments always appreciated!



Edit: HLVG per Allan Gould's suggestion below - http://www.pbase.com/prejto/image/151603452

Peter

[multiweb]

Very tidy shot and great scope. :thumbsup:

[allan gould]

Good image but a touch of green that could be taken out with HLVG and there is a drop off in star colour, but I like your processing as its not over the top.
Allan

[PRejto]

Thanks Marc and Allan,

I wasn't aware of HLVG but will certainly give it a go. I had tried desaturating green but that didn't work at all. I also totally agree about the star colours. Not very good. As I said, collecting colour data was very difficult. The images just do not pop out over the noise. I'm sure I needed longer sub frames but I was having so much trouble guiding I was ruining too many images so limited myself to 5 min. I've got to solve this issue before I try anything else. At the moment I'm not figuring it out...

Thanks,

Peter

Edit I think HLVG did the trick: http://www.pbase.com/prejto/image/151603452

[Larryp]

Lovely image, Peter-lots of detail

[alpal]

Hi Peter ,
that result is excellent.
I've always wondered about using a Barlow lens.
Seems to have worked well for you.

cheers
Allan

[allan gould]

Peter
That's a great improvement. Really pops now
Allan

[RickS]

Nice work, Peter! You'll need a lot of data to defeat the noise with that set up. Your f-ratio is almost f/14.

[RobF]

Love it. I can't remember the last time a saw a more detailed rendition, especially if you zoom out a smidge - the extra FL has paid off, even if you have more gray hair to show for it :)

[Ross G]

Great looking galaxy photo Peter.

So sharp and detailed.


Ross.

[prokyon]

Great result with many details and colors are nice too!

[PRejto]

Just a quick and big thanks to everyone that responded to my post. I always learn something through this exercise and this time was no exception.

Peter

[strongmanmike]

That's a really great and feature packed M83 Pete, congratulations :clap: Perhaps pushed a tad hard (I'm good at that too :lol:) so reducing the whole-image sharpening might be worth a look? Barlowing a nice refractor is a cool way of getting extra FL, albeit slower. I always meant to give it a try with my AP Starfire but never got around to it.

How are you finding the Morovian BTW, I hear they are pretty good cameras, did you get that from Steve Massey?

Mike

[Shiraz]

it was worth the wait Peter - that's a very fine image. regards ray

[PRejto]

Hi Mike,

Thanks for your words of advice. Yes, maybe I did push it a bit too hard. I've noticed different looks on different web browsers. On IE Explorer the image opens up to the size of the monitor (which might depend on how the browser is set up). Of course, if the screen is too large the image looks lousy! Just clarify for me if your comment about sharpening was when looking at it 1700x1438 pixels?

I did buy the camera from Steve. It is a nice camera and I think it cools quite well. The most frustrating thing about the camera is the lack of a native Sky X driver. The ASCOM driver does work to a point, but isn't very reliable. There is nothing nice about a freeze on downloading a 7 min subframe and needing to shut down the camera, re-cool, etc. Moravian promised a driver a year ago but they keep delaying! I do have some hope because Gaston (of ONAG) has become the dealer for Moravian in the USA. With so many people there using TSX I predict more heat if Moravian doesn't come to the party soon. At least I live in some hope!

Peter

[PRejto]

Many thanks Ray!

Some time ago I posed a question to you about the ICX694 vs KAF8300 and my TEC140. You wrote this:

"Hi Peter. Put the two options into the model. Looks like your scope would be a good match for either chip for hi res imaging down to about 2 arc sec seeing.
The 8300 will give you a much larger field of view.
The system broadband sensitivity will be about the same with either camera (the bigger pixels of the 8300 help with sensitivity, but lose resolution).
The 694 will have much better SNR (maybe 2x) at low signal levels in Ha narrow band due to the low noise of the 694.
The 694 will give you significantly better resolution (if you have a target that covers 100 pixels on the 8300, the 694 will put 140 pixels on it). that would be a noticeable advantage in good seeing
The 694 has a somewhat better dynamic range than the 8300, and the very low read noise of the 694 gives you more flexibility in exposure strategy.

Not sure if you want an opinion, but if it was me, I would push the 8300 as far as I could before deciding if I needed a replacement..."

I wonder if you have anything more to add now that you have your camera in service? Would the QE and low noise of the ICX694 help me with colour data if I try to image with the barlow again?

Thanks,
Peter

[Shiraz]

hi Peter. Nothing much to add - the 694 has delivered on spec in every way - no nasty surprises.

just some comments:
1. if you are needing to downsize to get the image looking better, why not start off smaller (ie without the Barlow) and upsize with drizzle stacking if you ever get good enough seeing. That strategy could get you to roughly the same result in 1/4 the time. In my limited experience, anything much finer than maybe 0.8 arcsec/pixel is a waste of time in Australian seeing and you are sampling way beyond that with the Barlow.
2. You could try binning to get low res colour data in a reasonable time (2x2 = 1/4 the time). That gives you something to do when seeing is poor and you cannot get high res lum data. You can get by with lower resolution in the colour data - doesn't harm the image too much if you manage the loss of dynamic range.
3. the 694 has about 30-40% higher QE than the 8300, so it will definitely reduce the time required to image at a given pixel scale. It would be very well matched to your scope if used without the Barlow at 0.96 arcsec/pixel (or 0.65 with 1.5 drizzle stacking if you got exceptional seeing). The low read noise of the 694 allows short subs to be used, which seems to improve resolution slightly (just an impression for now - have not done any experimentation). Short subs also fix many tracking issues and improve image dynamic range.

Pity you are not closer by - trying out the 694 could be worthwhile.

regards ray

edit: just reread your original post - you have tried 2x2 binning for colour - did it help and was there a reason why you did not use it for all of the colour?

[PRejto]

Hi Ray,

Thanks for your reply. Re colour 2x2 - pehaps I didn't try as hard as I should have. I'd worked very hard on luminance and had a nice and sharply detailed image. When I added 2x2 colour it washed out a lot of detail and added a lot of noise. But, my technique may have been the culprit. I've now changed the method of dealing with colour quite a bit and now think I might have been able to get a decent result from 2x2 alone. Actually the M83 photo is probably more 2x2 than 1x1. All the green was 2x2, and probably 50% of R and B. It's actually such a hogpog of shots over so many months I can no longer keep track of what I actually did.

Yes, I sure wish I could try a 694 chip camera before such a large investment! I do think imaging at .575 may have given me some advantage over shooting at f7 without the barlow. I only say that in comparing mine to several photos here at IIS and elsewhere, but the only real test might be for me to shoot the same object both ways and compare. Your drizzling idea might work, but generally I find - even at f7 - that my images are very noisy. Perhaps it's from using a light pollution filter, perhaps from not dithering, so I downsize them as well. The idea of a less noisy chip is quite applealing. But, as you point out I'd be giving up a lot of real estate.

Thanks again for your input!

Peter