I would think it would "hold" the weight. the question is could you use a
telescope on such a platform. There will be a certain deflection to any such
arrangement. (jump up and down on the roof and you will notice it moves).
Any telescope I have used needs a solid non moving base for any decent
observations.



Exactly. any roof is WAY too bouncy for a telescope mount, and your roof is
very lightly built by roof standards, with only 2x6's on 24" centers. Look
around the web for home built scope articles, they all use large concrete
foundations.

If the roof is the only suitable spot for viewing, you will need to add
something like vertical posts embedded in concrete and mount the platform on
top of them to isolate it from the building. Of course, then you give up space
in the garage due to the posts.

Dennis