The Greyt Telescope user manual shows this drill pattern, but doesn’t specify the drill diameter. We know they’re for #10-32 screws , but are they tapped holes or clearance holes?
I had the exact same question, but couldn’t afford to wait for an answer when we were assembling. After a bit of head scratching, we came to the conclusion that they should be a through hole.
Unfortunately we didn’t have the CAD available at the time, just the PDF manual (which frankly should be all we need). I also don’t have access now, or I would check the size of those holes now for you.
Long story short though, clearance holes for 10-32 worked well for us so far. Maybe @R.C can give a more official answer though…