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    Re: Doug Royer's Artificial Horizon
    From: Doug Royer
    Date: 2005 Feb 25, 11:44 -0800

    I haven't yet made one of the plexiglas artificial horizons you designed, but expect to. Any advice or experience you could pass along would be appreciated. One thing I'm concerned about is the problem of a base. How do you manage this? Another is that, with adjusting screws in the reflecting surface itself, I'm afraid I'd jiggle the horizon every time I touched one of the adjusting screws. Is this as much of a problem as I suppose?


    a little background on this 1st. Remember last year when you and George gave me pointers on the 1st(square)one I made? I took both of your  inputs and made a triangular A.H.
    I was experimenting making glass A.H.s that were square with 6-32 machine screw level adjusters.That configuration was extremely difficult to level out.
    The black glass surface was extremely reflective.However,I found it wasn't very robust as I cracked the glass at some point and the 3145 RTV didn't like to hold the glass to the aluminum base.Scratch the glass and back to the drawing board.
    The black plexiglass is 5/16 inch thick and triangular.It has 7 inchs/side with 1 stationary 6-32 screw in the left corner and 2 level adjustment 6-32 in screws in the other corners.These are 2.5 in long and the plexiglass is threaded so the screws allow direct leveling.The 2 liquid levels are positioned close to the edge and positioned on the top surface of the A.H. on  2 axis.I used a watery plexiglass adhesive to bond the levels to the plexiglass surface.The whole thing costs less then $ 20.00 to make.
    I found that if one leaves the paper on the bottom side of the plexiglass for some reason there is no double reflection.
    Leveling is not really a problem.Kick the dirt clean of clumps or pebbles where you are going to set up.Place the AH  on the area swept and screw 1st one and then the 2nd screw to adjust for level.This takes a few minutes but is not really that painful to accomplish.Once the bubbles are centered in each level leave it alone as it will be as level as you can get it.
    No problem in seeing the sun on the surface of the AH. I tried it on some stars and Sirius,Capella,Rigal and Aldebaran are easy to pick up.I found because of the weight,or lack thereof,of the AH that a wind can actually move or cause the AH to become off level.Place it in as guarded a spot(less windy)as can be had that still allows you to line up the bodies needed to take some cuts.
    This is a robust assembly.Care must be taken NOT to scratch or mare the plexiglass reflective surface as it is softer than glass.I take the screws out of the AH for transport and wrap it in a chamois.God knows those evil tempered horses tried their best to damage as much equipement as they could during the trek.The sextant and AH came through with only minor  blemishes.
    All this said now, I used this in a desert environment.Not much moisture in the air to cloud the heavens and "fuzz" out the body's image.Also,there was NO excess ambient light from the surroundings.It's very dark at night in the desert.
    I mention this as most listmembers reside in more humid/wetter climes and that may have an effect on the clearness of the reflections of the AH.
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