A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
From: Bill Morris
Date: 2020 Sep 6, 01:50 -0700
Firstly, I am pretty sure that your sextant is much older than the certificate, probably around 1930 or a little sooner.
The kit of telescopes is a top of the range selection and most of them probably had little use. The ones most commonly used were probably the Galilean"star" telescope and the zero magnification sighting tube. The former has no provision for collimation and it is irrelevant in the latter, which serves only to direct the vision in heavy weather. The prismatic monocular has no provision for collimation. That leaves the long Keplerian "inverting" telescope,usually of six power upwards to 12 power and almost never used for observations at sea, and the sighting tube, both with interupted threads for rapid location in the telescope ring. I cannot see any means of adjusting this for collimation, but a further view to show the ring, its vertical "rising piece" and the associated parts attached to the sextant frame would help to confirm this.
in ancy case, errors of collimation have to be fairly large to be relevant and have most effect at high elevations. If the telescope looks parallel to the frame it is good enough for ordinary purposes. You could use a small engineers square between the face of the frame and the face of the objective lens cells to check the star telescope and prismatic monocular and if a rising piece is bent, it could be persuaded straight with a soft mallet.
p.s. There is quite a good book which covers most of this: The Nautical Sextant by W J Morris...