gorann

Very skilful processing Wim! Cannot be done better and it is now among the best M31 images, as already said here. However, I notice one thing unrelated to the processing: there are starspikes, which I found can be avoided with curved cable management, as I did after seing those spikes in my M31 data. This is how I arranged my cables (shaped by taping them to a curved steel wire). Takes away all spikes.

I fully agree! I love what the RASA 8 can do, except for allowing tilt adjustment. The ASI2600 has a tilt plate but on the RASA 8 it is only accessible after unscrewing the camera which makes it rather useless. Someone should invent an acceible til adjustment to put between the camera and this scope! The new dedicated Artesky connection (although still no tilt adjustment) that I just received seems a bit less flimsy than the one that comes with the RASA, but I am clouded in so I cannot report on its performance.

Nice catches! usually I only realize that there is an un-forcasted clear night when I take the last walk with the dog just after midnight and then it is too late...... But right now I would be very surprised to get such a surprise here among clouds and fog🥴

Here is my flat run through the Equalize command in PS, which is used by many as a diagnostic tool to find banding and gradient problems and I see nothing there.

I wonder if DBE could create the problem. Like Gradient Exterminator in PS DBE can cause odd effects. If you have a good master flat then in principle you should not need to do DBE. Maybe @wimvb who is a PI expert can comment on this.

If I also have banding after an extreme stretch then it did at least not bother me during the processing - I never noticed it. So maybe it is something in your processing that brings it out to an extent that it becomes a problem for you. I only use PI for a few specific things (primarily stacking and a bit of DBE), and then do the rest including all stretching in PS so I have hard to come with any suggestions. By the way, at what temperature did you run the sensor?

Here is the raw sub if you want to do a direct comparison with yours in PI - I am more a PS person 😀 2020-08-15-1945_3-CapObj_0003.FIT

No, I did that and also an Equalize in PS which is extreme stretching and I do not get those dark corners. I do see a defocused star in the sky (showing that collimation is fine). Here is the most extreme autostetch option in PI

There is something in your image train that seem to totally cut out the corners, making them all black. I do not get that. The useful image circle of the RASA 8 should be 32 mm, so it should do better on the 28 mm diagonal of your camera, with some rather slight vignetting.

PS. I also notice that you have much darker corners in your RASA8 flats with the ASI2600 than I get. That is also quite odd.

Not sure about the ADU, I just took a series of 1 second exposures with the RASA 8 pointing at the sky at dusk, selecting an exposure time that kept the histograms for the colour channels away from being clipped. Here is what the histogram looks like (in PS)

Odd. I have only once taken flats with my ASI2600 and it was 1 second sky exposures at dusk (gain 0. cooled to -10°C). Here is what one such debayered sub looked like - no banding whatsoever.

Hopefully it is a cable issue. Keep us informed what you find out.

Well I have not seen them in my lights. Could it be a cable issue, with the USB cable being exposed to DC current from another cable? Hopefully someone here on SGL has an idea.

Well, that banding is odd - have you shown the flat to ZWO?

Why do you do DBE on a flat? In any case I found that flats are a mess with OSC so I wait until I really need them. Also with the RASA 8 the ASI2600 really have a bit too big chip, the RASA 8 is not really not supposed to light up more than a 22 mm diagonal, Anything you can get out of the corners are just bonus. But the colour banding looks odd - I have not seen that but then I have not imaged RGB with the ASI2600 under moon light. It could be a moon light issue.

Yes, I removed it since Celestron says you should do it if you use filters and I have also used the RASA with my ASI1600MM and Baader filter drawer. As you say that window has no purpose so better take it off, although it will probably have no major effects on your ASI2600 images. I have not taken any flats yet (almost sacritlege) - but I have no dust bunnies yet in my system and I fund that those dark corners can be easily fixed in processing or cropped away.

Yes, Vlaiv is of course right (as nearly allways). If you have another go at processing the data I think it could end up with something similar to that of Valiv's second image.

Goredeous first light Tristan! I had the same experience in August when I did exactly as you - point my new RASA8 and ASI2600 at M31 (https://www.astrobin.com/kv60c2/). Good object to test first light. And as you I was also pleased with everything except stars. That system is fantastic but at f/2 any little tilt will mess up stars. I think it is mainly us that process the data that really notice it but it is annoying. I had some night when the stars were ok but it is really a delicate issue. I just got myself a new attachment for the camera that also will allow for filters, and I hope it makes it more reliable against tilt. The Celestron standard attachment does not allow for repeatability in centring the camera as you will have noticed - you can wobble it around at will which is not very satisfactory. Here is what I got and will try if it ever clears here again: https://www.teleskop-express.de/shop/product_info.php/language/en/info/p11535_Artesky-2--Filterhalter-und-T2-Adapter-fuer-Celestron-RASA8-Astrograph.html

Good to hear that the filters perform! Thought it could be processing. Got nothing but grey skies in the forecast here too😣

Great first light! Nice details when zoomed in as you point out. But zooming in I also noted something looking like faint halos around the brighter stars - not a major issue but I hope it is not the Optolong filters since I just bought a set. Have you aimed at any really bright stars yet?

You are lucky! I cannot even see any moon tonight🥴 By the way, I have found focussing the RASA8 very simple - do not need any special device, and it holds it all night.

I completely agree with all what Olly says. You seem to be set at buying a colour camera and the ASI2600 is as good as they get - an outstanding camera with very low noise, no amp glow (so no need for dark frames) and a large field of view (APS-C). I cannot imagine that any CCD colour camera can compete with it's image quality, so forget about a CCD (especially colour CCD - I have hard to believe anyone would buy them anymore). Yes, you will probably be oversampling a little bit (except on that magic night when you are really lucky with seeing and your mount's performance) but that is no problem with this camera as Olly says.

The very best of luck with the RASA Steve! Does it mean it is going to be clear in your corner tomorrow? To remind you and maybe inspire you, this is what my RASA 8 and ASI2600 did during its first light, aimed on M31 during 2.6 hours back in August. The image is a bit low in the red so maybe I should collect some M31 Ha with the RASA if it would clear here too..... It is 1.94 "/pixel as you say but it is still a quite ok resolution so I now had a closer look at the core (with HiPass filtering in PS) and I think the resolution is good enough for being a wide field image of M31.

How does this one compare to US prices? https://www.astrobuysell.com/uk/propview.php?view=167429