joaquimsrs wrote in post #8037791
I'm sorry but I have a really newbie question. How is it possible you took 400 mins of this galaxy? I mean doesn't the galaxy move on the sky? How do you manage to rotate the telescope? And how many photos did you take? Why did you need to take so many photos? Wouldn't 1 long exposure photo be enough?
I know that this may be a real dummy question, but I really would like to understand.
To counter the rotation, you use an equatorial mount. See cloudynights.com's forums for discussions of this. You can also see my thread posted on this forum yesterday with my first galaxy shots, and I list the exact equipment I used (which is pretty much the cheapest setup available).
1 400 minute exposure would be nearly impossible due to satellites streaking through your photo, planes, or imperfections in how the equatorial mount tracks (things still drift slightly over time and have slight errors), not to mention the noise you'd get in 400 minutes! By taking 100 4 minute shots, you get the same amount of photons, but you have 100 samples of random noise. You can then average the 100 shots together (its called "stacking"), the noise turns to a paternless low signal, which you can edit out easily in photoshop, and everything else is pure signal....ie, the galaxy. The other upshot is if a plane flies through your shot, you only ruined 4 minutes of exposure, not 400!
cloudynights.com's forums are where I picked up all the info to shoot my first shots, there's a DSLR specific sub group on there with good info.