Next message: Bill: "Re: Backyard winter sextant observatory?"
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. <G>
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
