Roger, you wrote:-
" Years ago, someone gave me an “EBBCO” plastic sextant made by the E. Berkshire Boat Co., Wargrave, Berks, UK., and marketed by Davis Instruments of Hayward, CA, USA. Is this related somehow to the various Davis models being discussed in this thread?
Mine is well made, dated 1974, and came with excellent instructions for its use. The only thing wrong is the filters. It has two horizon shades and three index shades. One horizon shade and one index shade are totally (100%) opaque when I look through them at the noonday Sun. All the other shades show the Sun as a large green blob of glare with no distinct solar disk. These must be fairly recent chemical changes in the filters (within the last five years, I’d say), because I took sights with this sextant as recently as 2010 and don’t recall anything funny about the filters.
Has anyone else encountered this type of problem? "
I've just bought an Ebbco, intending to use it as a class demo piece.
Neat little package, generally easy to use, the moulded finish graininess may indicate some stabilising filler in the plastic.
One advantage of its configuration is that you can rest the sextant frame against your cheek, for stability, if you position the free to move telescope well forward in the frame.
The snag for me is the telescope itself - there's a lot of chromatic abberation. If all your shades appear to have 'gone off', it may be the telescope that's the root cause.
I've ordered a bit of 7/8" tube to make a sight tube, eliminating the telescope, I'll report back later .....