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Re: Instumental error?
From: Bill B
Date: 2005 Apr 20, 15:42 -0500
From: Bill B
Date: 2005 Apr 20, 15:42 -0500
Alex wrote > But when I made almost simultaneous shots of the same distance > with two sextants (The other was Bill's new Astra) and obtained > a correct result with the Astra, and +0.4 error with my sextant, > I finally concluded that there is arc error. Alex Remember these comparisons were made near midnight after a sailing-club get together (and boring Power-Point presentation) and included playing with tripod mounting sextants, and viewing Jupiter's moons with your binoculars-- at a picnic table with enough security lights around to blind an Indiana deer.If I recall, the target separation was calculated at 51d 6.8'. No adjustments required for abnormal refraction. (We did not adjust for sea-level barometric pressure corrected to 706.92736 ft above sea level ;-) The Astra consistently measure 51d 7.0 in your hands with my scope (IC -.5) so corrected to 51d 6.5' or -0.3' from target. I cannot, repeat the -.3 result. Over 50 observations indicate -0.1' in the mid-fifties range for my Astra.) I do not recall your averages for the SNO-T, but 0.4' sounds about right. Bill
