NavList:

I whole-heartedly agree with Ridge White.

I use a thin smear of waterproof marine grease for all moving areas of the sextant except for the rack, where a plain SAE30 lubricating oil seems to be of the correct viscosity. Excess grease and oil can play no part in lubrication and, as Ridge observes, it captures dust that eventually forms an effective grinding paste.

I suggest that sextants should, like mechanical clocks, be serviced occasionally, say every five years, so the grease can be renewed. Left for many years it eventually assumes the consistency of one of its main ingedients, soap.

Eventually, experienced experts like Ridge will all have disappeared, so it's as well to learn how to do an overhaul yourself. It's not difficult and you need not be terrified (as I once was) that you will destroy the instrument's accuracy for ever.

Bill Morris
Pukenui
New Zealand
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