A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
From: Ed Popko
Date: 2021 Oct 13, 06:39 -0700
Your A-12 bubble looks about like mine. And good image too.
The thread size used by my camera tripod and cameras in USA anyway, is "1/4 x 20 NS" . It happenes to be what the A-12's side tap thread was too. Tap tread designations have changed a bit over the years so the NS part may have changed.
Since my original bracket post, I have added three small thumb screws for leveling. Easy to do, just drill some holes in the hardwood base and tap them out. Why? With small leveling screws, I can simply put the sextant/bracket on a table without a tripod mouting. It's more convenient viewing from a small dining table on my outdoor deck. The table is almost level; the bracket/thumb screws are enough to perfectly align the sextant. It's so happens that the A-12's mounting tap is at or very near the sextant's center of gravity so it balances fine without fear of tipping over.