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A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: Perpendicularity Error and the Davis Mk 3 Sextant
From: Peter Monta
Date: 2017 Nov 14, 10:55 -0800
- take out any side error by adjusting the index mirror, thus aligning it to the fixed horizon mirror
- place cylinders as shown; put camera in the plane of all three upper marks; take photo
- swap the cylinders on the arc, take another photo
- verify that side error is still zero
The two line segments are spaced by 2 mm, which subtends 43 arcminutes from the edge of the index mirror when placed on the arc 160 mm away. The PDF of the stickers is attached, to be printed on full-sheet adhesive label paper. The reason the two readings are averaged is that one is unlikely to be perfect in putting the stickers on the cylinders or cubes or whatever.
Cheers,
Peter
From: Peter Monta
Date: 2017 Nov 14, 10:55 -0800
It looks like my Mark 3 horizon mirror is out by about 12 arcminutes. Not horrible, but could be better. Pictures attached.
Procedure:- find the vertical distance in pixels between direct-view and reflected marks; average them across the two photos; scale to angular units for final result
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