? dithering issue

[speckofdust]

hello all, would appreciate your advice. as you can see in the attached images, the stacked image of 7 Ha subframes is full of elongated hot pixels but the sub frame does not have any of these. The subs were stacked in deep sky stacker with darks and flats. funnily enough, the rgb frames from the same session did not have this problem. cooled camera asi1600 mm exposed for 10 minutes. Thanks for your help. I read a recent post which was discussing a similar issue and they mentioned something to do with dithering{ I am not sure what it is though}

[vlaiv]

You need to use sigma clip stacking here to remove trailing on hot pixels.

DSS is also not the best tool to calibrate your subs. It uses 16 bit format for that and sometimes that lacks precision. Hot pixels should be removed by darks, but they seem not to be properly removed and there is slight drift sub to sub which creates streaks.

7 subs is a bit low number to effectively use sigma clip, so there might be problem with that as well.

[speckofdust]

Thanks Vlaiv for your advice, will give it a go with the sigma clip, can I ask what tool would you suggest instead of DSS then. thanks

[vlaiv]

12 minutes ago, speckofdust said:

Thanks Vlaiv for your advice, will give it a go with the sigma clip, can I ask what tool would you suggest instead of DSS then. thanks

I personally use ImageJ for both calibration and stacking, but I think it is far easier to stick with DSS for stacking and only do calibration in different software - like ImageJ of something else (I don't really know that much about other software like Siril or similar - but I do know that you can do calibration there - maybe someone else will give advice here).