NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: Instrument Error
From: Fred Hebard
Date: 2005 Apr 24, 19:10 -0400
From: Fred Hebard
Date: 2005 Apr 24, 19:10 -0400
Bill, Here are the data with the mean date and time, UT1, and the altitudes. The location was 36*46.8N, 81*50.7W. The observation for 18 April is listed as for 17 April in the original table, where the separate dates are zone time rather than UT1. Most of the the time the sun and moon are higher than 20* altitude. Fred Objects Mean(Date&Time) D Sc Mc N(delarc') Mean(delarc') StdDev(delarc') Moon,Antares 23Sep2004 00:39:53 38 15 26 2 0.1 0.38 Moon,Jupiter 18Apr2005 00:54:43 58 26 75 7 0.5 0.21 Moon,Jupiter 20Apr2005 01:02:02 22 30 50 6 -0.1 0.28 Moon,Venus 06Oct2004 11:34:59 49 35 80 7 -0.2 0.26 Moon,Venus 07Oct2004 10:59:03 39 32 70 6 -1.1 0.23 Moon,Sun 20Sep2004 22:06:58 80 15 26 6 1.2 0.37 Moon,Sun 21Sep2004 21:11:26 93 25 17 6 1.3 0.49 Moon,Sun 05Oct2004 17:13:14 98 48 12 6 1.4 0.15 Moon,Sun 06Oct2004 15:55:08 87 41 40 8 1.2 0.34 Moon,Sun 08Oct2004 14:45:46 66 35 66 10 0.7 0.38 Moon,Sun 07Nov2004 15:27:00 63 31 51 6 1.7 1.28 Moon,Sun 16Apr2005 22:03:24 93 23 62 6 1.4 0.15 Moon,Sun 17Apr2005 20:18:11 103 44 31 8 1.2 0.24 On Apr 24, 2005, at 6:42 PM, Bill wrote: > Fred > > I am envious of your standard deviations, especially with the larger > angles. > To date every Sun/moon I have shot had the Sun to the west of the moon > (April 13, 2005 and on), and I prefer separating, so did try some > set-and-leave shots for separation. > > What I find interesting is despite different methodologies, scopes, > instruments and locations we both wind up over shooting the target > consistently (and it would appear we both saw the same Sun and moon in > April > ;-) > > What time(s) of day did you make your April 05 observations? As I > noted > before, while my STDEV's of error were horrible, the observations I > made > when the Sun and moon had Hc's over 40d turned out remarkably well, > with > mean errors in the 0.25' to 0.5' range. The "easy" shots with the > moon high > in the sky and the Sun in the 15d-25d range all had sub 0.2' STDEV > error > means, but error means were in the 0.5' to 1.0' range. Admitted the > instrument in in the hands of a novice, and I don't have enough data > points > to justify a firm conclusion, but it appears the lower the Sun gets > the more > I overshoot. There is not enough flattening of the Sun by refraction > to > account for the trend. If you are using Franks calculator, I recall > he did > have a correction for Sun/noon flattening, then disabled it. I do not > know > if he has plugged it back in. Either way flattening could only > account for > 0.1' or so. > > If memory serves, Alex had run test using the Sun for IE with both his > Galilean and inverting scopes, and saw little or no significant > difference. > > Still stumped > > Bill >