LooseFur

Thanks again guys, you are all extremely helpful! I took only 1 dark at the time, but I do use LENR. In hindsight I now know I needed more darks probably but interestingly enough, when I stack the 9 light frames with the 1 dark I get a worse result than when I don't (See my other thread here). I also have 40 odd bias frames taken at same ISO/aperture but at 1/8000 shutter speed. The lights were taken at f/5.6, ISO 6400, 4 seconds. f/5.6 is the optimal edge to edge sharpness of the zeiss (Milvus f/1.4) glass (coma aberration at wider apertures, bad star trailing at exposure > 4 seconds). I'm a pretty technical landscape photographer, I focus stack all my landscape shots but this astro stacking is quite new to me! As for noise, I am cutting it down a bit but as a focus stacking landscape photographer, pixel detail is a big thing for me! So I'd like to improve it. This snip is from 100% (pixel level) in the top left corner. Any hints on reducing it further would be most appreciated! Bear in mind this is 36mp. P.S. I am also pulling the image up about 3 stops in Lightroom

Thanks everyone for the replies, you're all very helpful. I am actually not an astrophotographer, per se - I am a landscape photographer so I don't have motorised/equatorial mounts, and I am shooting using a 35mm Ziess lens (incredible optics)- as such there was no tracking. SO, the stars would be on different pixels for each frame due to earth rotation. If I wanted to dither, I'd have to do it by hand. Pretty tricky to move only a few pixels on a ball head tripod but I have a steady hand, I guess. Seelive, what you said makes sense, but maybe for tracking mounts? Bear in mind I just use a 'regular' tripod.

hmm interesting, but what I was proposing is to crop the images, in a manner which shaves off different sides each time, so the noise would not be relative to the stars in each image. So, for example for image A I crop it losing pixels from the bottom and right sides. For image B I crop it to lose pixels from the left and top sides and so on for various permutations. Would that work?

Hi all, I use a nikon d810 (high megapixel count) and learnt about dithering after a night shoot (of course!). I understand it means to move the camera/telescope a few pixels randomly in the hopes to reduce noise (pattern/random) when stacking. However, for my night shoot recently I didn't move the camera at all (I didn't know about dithering). So, my question is, can you 'dither', after the fact - i.e. does cropping the images you have taken (I only did 10 lights) in random directions simulate the dithering effect? So long as all images are the same size? Or is this idea flawed? When you have 36mp per file, a small amount of cropping is insignificant if it means I can reduce some of the noise. Looking forward to your replies.

Maybe I managed to corrupt mine ! I will try this later. Thanks, I will also try this later

Interesting developement, I stacked again without the dark frame and that strange line noise is gone. Strange?

Thanks for the reply, I didn't know about the shift key trick! I actually tried this (and then used the comets & stars mode) but the resulting image is a bit strange too

Hi all, (Very) long time lurker here, first time poster! I am struggling with stacking some images I took the other night and I know there is someone here who can help! When I stack my light frames in Deep sky stacker, there seems to be some strange 'line noise', please take a look at the images below. Has anyone seen this before? I simply use recommended settings in DSS and export it as 16 bit TIFF (I plan to process it in lightroom). I know f/5.6 is a narrow aperture for this type of work (I used high ISO to compensate) but I know my gear and f/5.6 is pretty optimal for the Zeiss Milvus f/1.4, anything wider and I get unacceptable coma (the joys of high resolution sensors). There is a comet in the shots, but when I try to 'mark' the comet prior to stacking, it doesn't allow me to actually mark it (although it allows marking of some not so nearby stars?). So, I don't use the comet stacking mode. Any help greatly appreciated! Stacked crop: Original crop: original: You can see here, that it won't allow me to mark the comet itself. I am fairly sure there is something wrong with what I am doing here but please let me know!