Sark17 wrote:
Okay so last night I was simply trying to practice with my Intervalometer. I aimed it at the stars and did 30 30 second shots, 5 seconds apart at f/8 ISO 1250 bulb mode. Why are there no star trails? I was using the Canon EF 14mm 1:2.8 L that I mentioned in the OP and the EOS R. I wasn’t trying to have a nice scene or anything, just practicing with my new timer, but I figured I’d have at least some star trails at 30 seconds?
It's good to practice first but the intervalometer is not night dependent, leave the lens cap on and practice in the day. To save the batteries switch your parameters to a 5 second exposure every 35 seconds. As for the star trails, how about we just try for a single good quality shot of the stars first and then expand our horizons.
You used f/8 when you should have been using f/2.8 or the widest aperture your lens allows. Use the 500 rule to acquire sharp stars. 500 divided by the focal length of the lens which in your case is 500/14=35.714 or 36 seconds if using a full frame camera and if using a APS-C first multiply the focal length, in your case a Canon, by 1.6 so 14*1.6=22.4 then the 500 rule 500/22.4=22.321 or 22 seconds.
Try setting your ISO to 1600 at 22 seconds and if the sky comes out too light then shift it back to 800 at 22 seconds which is simply a 1 stop difference and see what that looks like. You want to find a nice balance between dark sky and light stars to save time and effort in post.
All that said, if you truly want star trails then you can leave the shutter open for as long as your batteries and sensor hold out. But, to save your sensor from over heating use shorter times such as 1-2 minutes, f/2.8 and either 200 or 400 ISO, depending on what you think looks good, (note: increasing the shutter speed means lowering the ISO to get equivalent results, decreasing ISO means less noise to deal with) and then stack the results.
Assuming you like the results from 22 seconds at 1600 ISO then;
44 seconds requires 800 ISO
88 seconds (1 min, 28 sec) requires 400 ISO
176 seconds (2 min, 56 sec) requires 200 ISO
At longer times a few seconds over or under will not show any real difference.