That's rather cool JP
At that focal length however, you will need to utilise some form of guiding....may as well keep with the trip down analogue memory lane nostalgic theme and whack a guide scope, with illuminated retical, on the side of the 8" and eyeball guide your 30min subs
Where or how do you develop the film and do you scan the negs or make prints or both?
I did
THIS back in 1984 with my 8" F7 Newt, using piggyback eyeball guiding, (crappy drive)
this is a scan of an old print, so the quality suffered further
Very cool that someone would bother to have a shot at things, as we did them 40 years ago
Mike