I once did a setup where I wanted to have the moon traverse most of the diagonal of the 135 frame. I didn't have a long lens so I was tring to get creative
I cant remember the specifics but I think the exposures were in the 20 minute range.
I screwed around with the whole roll and remember I surprised how much it did move even with shorter exposures. The shorter exposures didn't work too well, the moon was just blurred with no detail.
I'm sorry I can't help more but at least you recongnize there will be some movement.
Good luck and share your results.