NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
From: Paul Dolkas
Date: 2015 Mar 25, 11:41 -0700
All-
I have a Davis 15, which has a micrometer drum so it’s more accurate, although it’s also made of plastic, so it suffers from the same thing as all plastic sextants – they warp in the sun. Especially true of black sextants. I have to let it sit outside for a half hour, true out the mirrors, take my shot and then recheck the mirrors to see how much it’s warped in the 5-10 minutes I was taking a shot. It’s not unusual to have an index error of a few arcmin at that point (so I take half of that and use it as my index error).
There’s a reason better sextant are made of metal, and painted white for use in the tropics.
Paul Dolkas
From: NavList@fer3.com [mailto:NavList@fer3.com] On Behalf Of Alan S
Sent: Wednesday, March 25, 2015 11:07 AM
To: paul@dolkas.net
Subject: [NavList] Re: Art and Navigation
Carly:
I'm no expert, nor do I make any claims to expertese. That being said, the Davis sextant you mentioned, plastic frame, will work, I've used one, shooting the sun while standing on the beach in North Carolina, I don't have a boat and tend toward seasickness, so I "navigate" standing on the beach, or using an artificial horizon in the parking area at home. Due to materials of construction, these instruments will sometimes give "odd" readings, but they do work. By the way, have you tried the telescope for shots, youmentioned using a sight tube.
Eventually, while feeling flush, I bought an Astra sextant, metal frame, a much better instrument, though a lot more costly. Depends on how foolish one wants to be re spending their money. Your father could likely make some good suggestiis re a quality instrument, as could any number of people at NavList, it boils down to how much you want to or are willing to spend, thougth finding a "bargain" is always possible, perhaps but not likely, but possible. Good luck.
Alan
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