There is one question I ponder about since I started with astrophotography:

I know I am looking way back in time.

I am sure the deep sky objects change all the time. A nebula expands at certain speeds, a star is moving along, material is moving or hit by something else, objects might interact, etc. .

So when are we able to notice changes in light-years-away deep sky objects like a nebula or a galaxy?

When I take a long-term exposure of an object and repeat the same shot a year or more later, shouldn't there be a small noticeable difference? Or not because the target is light-years away and appears so small when observed from the earth?

If I combine long-term exposures taken every year to a single image I think I am falsifying the object somehow. Or is it simply not possible to detect seemingly small changes with the technical tools available for the moment? Or could it be the distant targets movements are way to small to be detectable by any observer on earth?