LA3QMA
Think about what happens when you shoot pretty much anything other than the very bright M42, like say Horsehead Nebula which is relatively dim. You may see little or no detail in the first 10 second exposure and it can minutes before you see anything recognizable and hours to really get nice detail. Well with the mosaic it covers the frame in very small slices working right to left (in the northern hemisphere), so even at only say 1.3x it could take 10 minutes worth of exposures before it fills the whole frame one time. It will have a fair bit of overlap in the middle/left and possibly almost none out near the edges/corners. It means for some objects you really need it to just let it go back over it many times. And pretty much no matter where you decide to stop will be somewhere "in the middle of a pass" but generally the later exposures have less and less effect so you just have to decide when it's good enough.
Tonight I am in fact imaging Horsehead Nebula (IC434) and what I saw was that every individual exposure was producing quite a lot of noise especially around the corners/edges (maybe from light pollution), so after one full pass, what I saw was a ton of diagonal banding across the frame as all those noisy corners were in regular lines. I'm 35 minutes of exposure time in, and those bands are becoming less noticeable with repeated passes. Unfortunately it looks like as of a few minutes ago I'm now at 100% stacking errors so I may be done for the night, and not know if it ever really gets
better than this. I don't see anything blocking the view, so not sure why it failed, but I think others have reported the same issue. At some point it just gives up. Known bug, no update with a fix yet.
