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    Tripod Mirror Artificial Horizon
    From: Ed Popko
    Date: 2015 Apr 20, 16:16 -0700

    I have had some nice day/night shooting sessions with an artificial horizon I made from a 14" diameter polished plate glass mirror and simple wood leveling frame supported by a surveyors tripod ($35).  The mirror is not optical quality but probably less prone to error than my personal errors with a sextant (Cassens/Plath). The tripod has pointed supports which are pushed into the soil with your feet. It's gives a very stable platform unaffected by wind. The plywood triangular base and mirror support are then attached. Finally, the mirror is leveled with a 12" Starrett beam machinest level placed on the mirror and above each of the three supporting sides of the triangular support frame. Thumb screws make fine adjustments.

    On the perimeter of the mirror, I have small stick-on paper circles with their azimuth.  I rotate the mirror till the mirror's 'compass rose north' points more or less to Polaris. Thus a crib sheet of star heights and azimuths prepared ahead of time can be knocked off very quickly.  My back yard has some viewing blind spots due to tall trees but 270 degrees are fairly open.

    I'm able to shoot anytime during the day and for about three hours at night before the temperature change deposites a fine dew over the glass (no heater element like telescope guys use).

    You can read faint stars 360 degrees with the setup start the faint ones start dropping as the dew builds up.  An unanticipated safety consideration is setting it up in bright daylight. Unlike artificial horizons that use water or motor oil, the reflection of the sun in the mirror is nearly 100% so you have to be careful not to be blinded by the sun's reflection. 

    Ed Popko

    Woodstock, NY  (yes, that one)



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