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    Re: Home made artificial horizon
    From: Bill Morris
    Date: 2011 Oct 2, 12:44 -0700

    Welcom, Randall.

    I used artificial horizons a lot about thirty-odd years ago and found old sump oil in a deep oven roasting tray to be very good. I was in an area with little light pollution and stars were easily visible. Cooking oil made dark with food colouring is less messy. Paint the inside of the tray black. Mercury is ideal and fairly benign (though its concentrated vapour and organic compounds are certainly not), but it is expensive and difficult to obtain because of postal restrictions around its supposed toxicity.

    Making a worthwhile mirror AH is quite difficult. The level needs to be sensitive to better than one minute per 2 mm bubble movement and such levels are expensive engineering instruments. You can cut down the cost by buying just the vial and sticking it to a metal base with plasticene. You also need a tribrach (base with three adjusting screws). It is difficult to make one that doesn't wobble as you adjust it. The main problem is making the screws a tight fit in their nuts. This is likely to be beyond most non-engineers.

    Patrick Goold has no doubt much to share with you on this topic of making a mirror AH. Personally, I would opt for sump oil in a roasting tray.

    Practically any metal sextant will be better than a plastic one, and this includes quite antique ones. I have bought sextants from Australia, New Zealand, Malaysia, India, the Ukraine, Russia and the USA and have seldom been deliberately deceived by sellers. You do need to look very carefully at the pictures on e-bay and to ask questions if you are in doubt; and be prepared and willing to do your own overhaul. To the list of types that another member has posted, I would add Hughes and Son (old but good) and the very fine SNO-T (SNO-T in Cyrillic characters).

    Reducing sights with a scientific calculator is at least as quick as using tables, is cheaper and takes up much less space, even with a spare. John Karl's "Celestial Navigation in the GPS Age" gives some very good guidance on procedures.

    Bill Morris
    New Zealand
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