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Ivan, For all moving parts of the nautical sextant except for the rack and worm I use waterproof marine grease. For the rack I use SAE30 spindle oil. The grease for optical eye pieces is a very sticky black grease. I don't know whether it is graphite grease, but it is also intended for use on things like exposed universal joints and sun and planet gearing, where an ordinary grease might simply be flung off. If the grease your mechanic has given you is thick and very sticky, go ahead and use it on the multi-start eyepiece threads.

As an aside,where grease is required on aeronautical sextants I use silcone grease rated for low temperatures, even though I have no intention ever of using them at altitude.

Bill Morris

Pukenui

New Zealand