|
Good threaded connections shouldn't introduce tilt but as Joshua suggests, images of your components at the moment can be good way of seeing where the weak point is.
Also, does the tilt change as you move from east to west or north to south?
As for every filter having a different background brightness, that's completely normal. Different moisture contents in the air change how bright the sky can be. It's easiest to just pick an exposure that is suitable for the best of nights (moonless and good transparency) and just use that exposure. You'll waste more time trying to get the perfect exposure for each filter every night for next to no gain in image quality.
|