A rule of thumb method to calculate the maximum exposure time, for a particular focal length, before star trails become noticeable. It's simply 600 / focal length = exposure time (in seconds).I can't help you with the stacking thing unfortunately
but I gotta ask why use f/8?
I use 2.8 on my 16-35 with the focus set to infinity..
That way you can keep your ISO down to a minimum and get less noise at
the same amount of time.. using the 600 rule...
If you have a 30 Sec exposure using ISO 6400 @ f/8 you can go down to
ISO 800 @ f/2.8 and still have a 30 sec exposure..
You'll still get the sharpness you need..
What is the 600 rule?
For a 50mm lens, 600/50 = 12 seconds.
For a 15mm lens, 600/15 = 40 seconds.
By keeping the exposure to those times or less, the stars appear as dots, not trails.
Wow...talk about a VERY informative post for a noob!!!!
Thank you very much!
ps. Do you have any insight into what stacking photos are? Is that similar to HDR photography?