"Star Color Calibration is not possible"

It looks like the problem is applying the dark. But if I remove the dark I get bad amp glow. Attached is reprocessed with flats and bias only, no dark. Finally, a calibrated subs... doesn't look too bad and amp glow is gone.

Interesting, how did you take the darks, what paramaters were used for that? Did you have similar issues before with darks?

This is the first time I've used darks because I switched from a (Pentax) DSLR to a ZWO ASI294. The Pentax never had serious bias or dark noise problems. But I just discovered that if I neutralize the background in the calibrated image, it looks like the stacked image. So tried turning that off in the normalize tab. attached is the result. All the colour is there but the red is quite suppressed. I can boost the red in post (Lightroom) but the final image is colourless compared to when I don't use the dark frames. Is this really a camera problem? Too much dark noise?

Did you try calibrate background and the star color calibration? That might help a bit. Neutralize background is just a more general, quick neutralization. With the Calibrate background option you can het a better neutralization. After that you can also increase saturation on the lower side of the panel on the right. You can increase the slider with SAT from 0.15 to something like 0.25 to see, and sometimes decreasing SAT. Th. below it from 0.25 to 0.2 also boosts that. Not too low though as then you will increase background color noise.

The reason why the darks cause an issue I don't know. Would you want to upload some darks and some light to our server? Login/password: appuser
Please create a directory named 'astrogee-darksIssue'. I can then have a better look at it.

I just tried your suggestion, using background calibration and then I got the "Star Color Calibration is not possible" error message again when I tried to do star calibration, so I quit star calibration and tried the saturation control to .25 and there was no visible change in the image. Yes, I'll send some images. Maybe they aren't good. My flats are not that white either - sky flats - but when I used Nebulosity, this was not supposed to be a problem. Thanks for you help.

The files are uploaded now. Thanks again.

Thank you I will have a look, I'll try to let you know tomorrow.

Just an idea..

At the start, did you use the right settings for your camera in the 0) RAW/FITS tab, on the left side of APP.. ?

I mean the right pattern for your sensor (like RGGB), and ticked force bayer CFA. ?

CS !

Posted by: @betelgeuze

Just an idea..

 

At the start, did you use the right settings for your camera in the 0) RAW/FITS tab, on the left side of APP.. ?

I mean the right pattern for your sensor (like RGGB), and ticked force bayer CFA. ?

 

CS !

Thanks but no, its supposed to automatically detect that info from the fits header, which is seems to do correctly.

My apologies, life got in the way. I'll have a look at it right now.

Couple of observations;

1. APP, for some reason, tags the lights with Mono. So I manually selected them to be RGB, it might be this tag isn't in the ASI fits file so APP can't see it properly. Tagging it like that shouldn't influence anything though.
2. Your Bias frames are black, there is almost no signal. It's better to take the bias frames with exposure times of about 0,05 seconds as it has a CMOS sensor, these have issues with exposures of almost 0 seconds. So the Bias is not going to be correct which will influence your result and is likely the cause of the failure to do proper calibrations down the road.
3. Your Darks seem to show light bleeding through. I think I see a light patch in the middle and even some dust, this will not produce a proper dark, also influencing your result. You'd have to find the source of that light bleeding (Newtons can have that coming through the back mirror for instance, covering that helps).

Given this I stacked without any calibration data and this was produced;

This proves the calibration data to be the issue. Lovely signal btw!

Then star color calibration;

Slightly green, so I changed the slopes for Magenta - Green to have a constant of -0.05. Which looks better to me.

And upping the saturation a bit, Sat. Th. down to 0.2, Sat to 0.25;

Thank you Vincent. This is a big help. I should have been more careful, especially with the new camera. I noticed a problem with the darks the first time and re-did them but obviously not correctly. I'll do both bias and darks off the scope with a cap on the camera, like I used to do with my old camera - I don't want to waste a dark sky on darks! Thanks for the endorsement on the data. My effort's are to expose as long as possible. Its turning out well 🙂

Oh well, these are exactly the times where you're learning a ton about what calibration does, I kind of liked it when I was getting very frustrated with some issue when I started, it meant I could solve that and understand it way better. 🙂 So good on you!