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| The whole Davis 25 with the prismatic monocular fitted |
The Davis Mark 25 is good value for a back up sextant, and while not as accurate as a metal one it is lighter and cheaper. Its main failing is you need to calibrate index and side error every time you pick it up.
During the Covid 19 epidemic I am on lockdown and can't go to Tui but I have the Davis 25 at home and I am practising sun sights with a baking tray of water or oil as an artificial horizon.
It has a little x3 plastic telescope. It us actually better than it looks and x3 does help. But I don't have great visual acuity and more magnification would help at least on land
I bought a cheap 8x20 miniature monocular. The objective lens is in a conical tube that unscrews. This allows it to mount in the front scope bracket and tightening it centres the monocular. The frame that holds the prism and eyepiece fits flush against the rear scop bracket and while the whole is to big it still holds in firmly.
I get a clear sharp view of the sun and its reflection and the field of view is about 5 degrees wide which is plenty. Of course the sun appears bigger and for me easier to judge when superimposed or "kissing".
I paid only £2.69 for this
on Ebay, they have gone up to abut £5 now. Just search for 8x20 miniature monocular.
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| The new prismatic monocular fitted, and the standard "x3" (in practice more like 2x) telescope underneath for comparison |
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| Showing how the mounting works |
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| A dimensioned photo from another ebay listing |
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More ebay listing photos. The optics are coated and so the objective appears orange from outside. In practice the magnification is more like x5 thanx8. Don't trust the description!
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