AbsolutelyN

Just now, gorann said:

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?

Yes agree, maybe I'm digging too deep into the files and you are bound to find artefacts. I do stacking, DBE and star reduction in PixInsight, most of the rest in Photoshop. However I do challenge anyone to process the attached file (M31 stack of 4 hours with no flats) and not find the banding in the image - it's pretty prominent once you run a DBE and start to work on the image. 

Temp was -10 but I got the same at -20 a few days earlier so don't think it's temp dependant. I'm using 2 min exposures form Bortle 5. 

integration4.xisf

28 minutes ago, gorann said:

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 49.77 MB · 2 downloads

He is my master flat for comparison

FLAT_CALIBRATED_BIAS_DARKFLAT_NEW.xisf

34 minutes ago, gorann said:

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 49.77 MB · 1 download

Brill thanks. Mine was a master flat but your single frame is very similar. If I apply a screen transfer function you exaggerate the fall off at the edges. 

Even more interestingly if I run a DBE and then STF you can actually just about see the same banding though not as strong. Probably because my flats are darker and it was a master flat. Maybe it is integral to the sensor after all if it's on more than one copy of the camera. 

2 minutes ago, gorann said:

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.

Pretty sure it's just the STF auto stretch exaggeratig the light fall off - if you look at raw de-bayered flat in PS it's similar to yours. I suspect if you do a STF autostrech in pixinsight you'll get similar. 

4 hours ago, kirkster501 said:

You need to be very delicate with HDR multiscale transform, if that's what you are using.  The default is much too aggressive.  I use a range mask and set the scale to 8 or 9 with lightness mask ticked

I think it was mainly Topaz Denoise in Photoshop that I must have used too aggressively - probably amongst other things.

Here is version two which I hope addresses some of the original issues. Sure there is still much that could be improved.  

7 minutes ago, kirkster501 said:

Splendid picture.  If I may say, to be constructive, I think you have gone slightly too far with the sharpening and HDR.   Here is my version with same sensor, which needs more processing:

 

 

 

Thank you and yes completely agree - I've been working on a second version which has less aggressive sharpening.  Always learning. great image. 

12 minutes ago, gorann said:

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)

My flats look similar in photoshop - screenshot has a STF stretch in PixInsight so is exaggerated. My darks are slightly darker I think. 

Just now, gorann said:

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.

Now that's what the flat should be like. What ADU are you exposing at? Although you can calibrate the banding out I do now suspect my camera is a dud. I've asked FLO about possibility of replacing it so will hopefully get it sorted. 

12 hours ago, gorann said:

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

Well I took new flats on my Esprit 80. Different computer, shorter better shielded USB 3 cable and different power supply. The banding is still there and clearly visible with nothing more than a STF stretch.

1 minute ago, gorann said:

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

Will do, thanks for all the help. 

2 minutes ago, gorann said:

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.

That's an interesting point thanks. I guess I can test that by removing the camera and taking new flats with a short USB cable and laptop to eliminate anything that might be interfering in my current setup as that is a possibility.   

5 minutes ago, gorann said:

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

Yes I sent ZWO screenshots of lights, darks, bias + flat. All I got was a one line response saying please calibrate with flats. And indeed calibrating with flats comes out with a pretty much spot on image. I don't see why I should need to use flats though. Very strange, I'm keen to know if anyone else has this banding or it's just my camera. 

1 minute ago, gorann said:

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.

I don't do DBE on the flats 🙂 I only did so as I could not figure out where the banding was coming from and did a DBE to see if it was embedded in the flats too - which it is. 

Didn't think of moonlight but it can't be that as the flats have the banding and they were taken in daylight. Perhaps it does not matter as I know I can get rid of it now but it's taken me a week to get a usable image out of the camera, was almost at point of sending it back.  

Just now, gorann said:

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.

 

That's interesting. I was not planning on taking flats either as I've never needed them with the 1600MM on the RASA. However I found I cannot stack the images without flats as I get the same banding pattern shown above when I stack the lights which makes it impossible to use the camera without flats. No sign of the banding in the darks or bias. Contacted ZWO and they just said you need to use flats. Not sure if I have a dud camera or this is inherent to the chip.  Lights without the flats look like this which is just unusable. 

3 minutes ago, gorann said:

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.

I'll have a go at some point over the next few days. It was a lot of firsts and rushed processing during a lunch break so can probably come up with something better. Suspect the biggest flaw in processing this is using Topaz De-noise. It's really good but often produces that painterly effect so need using very carefully. 
 

7 minutes ago, gorann said:

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

 

I saw the Artesky adapter and was tempted but not planning on using filters. Currently using the Baader 7.5 mm T adapter.  It would be good if Celestron just redesigned the front plate for better / repeatable image quality. As it is every time the camera moves it feels like pot luck on your star quality. It's done better than I thought though. 

Two questions though if I may? 

1. Have you removed the optical window from the RASA? Feels like just an extra piece of glass in the optical train but I'm worried if I remove it it might make focal position different. 

2. If you run a DBE on your flats do you get this banding pattern?

7 minutes ago, vlaiv said:

Do you mind me being slightly harsh on your image?

It's not actually the image, but rather processing. I think you obliterated the image . Again, I'm sorry to be so harsh, but seriously, I think you went too much with the processing. It looks more like painting than photograph.

Let me show you what I mean.

If I were to show this to someone and ask them, what do you think is in this crop, how many people would respond correctly and say NGC206, or at least - yes, that seems to be some sort of star cluster?

I think that above crop can easily pass as planet surface or similar.

Here it is on another image - same region

If anything, in second image one can clearly see that scattered dots are in fact stars.

I readily accept your (not so) harsh criticism. That's a really good example and I intend to try to learn and improve.  

21 minutes ago, ollypenrice said:

That's a splendid M31, very obviously. Great use of a fast system, despite the moon. You've also preserved a hell of a lot of detail into the core, which is always tricky. I think you have as much as any image I've seen. It's a great image. Once we regard this image as top notch (which I certainly do) we ask about reservations. I have two: As is often the case with OSC CMOS cameras I think it is red-biased. More blue signal would be nice. The other is that the sharpening does rather shout 'Pixinsight' to me. (Go on, shoot me down and tell me it was all Photoshop! 🤣) No but, seriously, I do feel I'm seeing 'wavelets' more than I'm seeing details in M31. If the image were not of the quality that it is I wouldn't mention either reservation. They are minor.

Olly

Thanks Olly, that's really appreciated feedback. Sharpening and denoise was indeed Photoshop (not PixInsight) and I did wonder if I'd gone overboard on both sharpening and saturation. It was very hard to bring out the blues which is probably why they've ended up more purple than blue - first ever image I've processed from a OSC camera. As I mentioned earlier I think it's just one of those I probably need to revisit and process again with a fresh eye. I was just so relived to get the calibration sorted after days of issues with banding so probably went overboard in a few areas in my excitement!  

27 minutes ago, ultranova said:

Killer camera and scope combo ,

Loving the image,

the only thing I would say, and this is obviously personal preference,

where you have gone quiet deep with your setup, the Galaxy looks a little washed out

as there is so much lum / brightness  , detail and resolution are out standing and the colors

are great. 

well done 

Paul

Thanks Paul, that's much appreciated. I think I know what you mean. Perhaps more contrast in the arms and darkening the haze around the galaxy may improve it. I'll take a look at that and see what I can do. Sometimes it's best to process an image and then leave it a day and come at it fresh again. Much appreciated. Tristan

2 minutes ago, DaveS said:

That is phenomenal. I've just been scrolling around the full res on Astrobin, and it's gorgeous.

Thanks Dave. Wasn't expecting much with Moon so bright. Had awful results from these frames for last 5 days but finally figured out the calibration process. 

40 minutes ago, Phillyo said:

Haha yeah, there's always something that needs tweaking or tinkering. I think we're our own worst critics half the time!!

True but I find you learn quicker if you are a harsh self critic. Saying that I don't think I can fix those stars as APSC is too big for image circle ... so perhaps best not to worry :-)

2 minutes ago, Phillyo said:

Absolutely stunning. I love M31 and this is top notch. The level of detail is phenomenal. I took a similar image recently with the 533 on a Samyang, slightly wider than this though. Didn't get this level of detail from it.

Thanks. I think the detail is simply due to the 8" aperture. The detail here is far more than I got with my Esprit 80 / 1600MM. Just wish the stars were pinpoint across the frame. 

Finally got first image out of the new 2600mc. 4.3 hours on M31 with the RASA 8 - 128x 2 min exposures with 80% moon in bortle 5 at unity gain.  
Higher res on astrobin - https://www.astrobin.com/grod4i/

Re-processed to address aggressive noise reduction. Background is a bit lighter to try to pull out what I think is some faint HA in the background. 

Original:

Also the green / magenta bending doesn't seem match the bias or dark files - green/magenta seems more fixed width and regular

Bias


Dark:

1 hour ago, tomato said:

I’ve got the same scope, sensor(QHY 268c) and target, (180 x 60 sec). I took flats and dark flats today, as soon as I have some darks, I’ll attempt to process the lights and let you know what I find.

I have found on-scope darks hard to do with a RASA as the cover on the scope stops the camera cooler dissipating heat so it cannot maintain the temp set point.

Thanks. I can make my files available for comparison if needed (I'm worried I'm just not getting the calibration process right).  All 120 sec exposures. I've not got any flats and have now removed camera for second set of darks. First darks were on well covered scope at night, second set with camera capped and covered in tin foil. Made no difference. Also have lights/darks at 100 gain and 0 gain and still have same results.