Wow, Gary, what a ripper, Iridium +. Reminds me of an image of McNaught I took late on in its show when i had a meteor zip through beside it. Not as specky as that.
50mm 'eh.
Might give it a go with that one then. It's certainly a better quality lens than my 28-90.
Do you still have the original images? Would the ISO be recorded in the Exif details? I don't know 'cos I've never looked at the Exif before.
What was your exposure length on the tripod one? did you get trailed stars?