NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: Open a Mk IX bubble sextant
From: Jean-Philippe Planas
Date: 2023 Nov 4, 10:05 +0000
From: Jean-Philippe Planas
Date: 2023 Nov 4, 10:05 +0000
Hi there,
Yes you may open it by splitting the two halves ( 4 long screws to undo) to clean and lubricate the inner mechanisms. It is harmless.
At first don't try to refill it. These instruments rarely leak their fluid. It might still be fully operative, all the fluid being currently stored in the fluid reservoir. Try to form a bubble before any other action in this respect.
The same goes for the averager that is a bit finiky to regulate back once it has been fiddled with. Just verify it runs for two minutes and works fine.
Set the angle sight at a fixed angle, run the averager for its full duration ( two minutes) and verify the result is the same as the preset (untouched during the averager work) value. Duplicate this experiment with several different preset angles. For instance 0°, 20°, 45°. There is a strong probability that the precision achieved is still acceptable. Difference between preset value and averager value of 1 or 2 arc-minutes).
Bill Morris might provide more precise and in-depth advise on this matter.
Good luck,
JPP
On Saturday, November 4, 2023 at 12:17:50 AM GMT+1, NavList Community <navlist@fer3.com> wrote:
I got a Mk IX bubble sextant with an averager 'clockwork' assembly attached and need to open it for cleaning and refill of the bubble, is it safe to remove the right (from the user's perspective) half to get inside?
Generally I am pretty confident with this kind of work as I have repaired a number of old cameras and shutters but am slightly worried some adjustments will be destroyed or way off in the process. Specially I wonder if the averager can be left in place? I imagine some (awkward) calibration may be needed if I jumble too much?
A few tips would be very helpful!
Cheers Micke
