NavList:

Randall,

To give an example of what can happen for lets say reading the sextant micrometer drum in low light conditions (see img 1153). The vernier scale on the pictured micrometer drum can accidentally be read as 36.6' instead of 32.6' if the bottom is used as the reference instead of the top. If we run a sight reduction for Denebola for 116* 32.6' artificial horizon then the intercept is now 1.8 toward. This would be on the short list of possible errors.

Greg Rudzinski

[NavList] Re: 11 body sight run, all under 4 miles! Love this instrument!
From: Greg Rudzinski
Date: 20 Apr 2012 11:37
[NavList] 11 body sight run, all under 4 miles! Love this instrument!
Randall,

You have discovered the virtues of a metal sextant :)

Check on that Denebola observation. A 3NM discrepancy from a known position verified by chart or GPS is the point where I suspect an error somewhere in the CN observation, reduction, and plot process. Most of my discovered errors are the results of misreading the sextant, watch, or table look-ups. Transposing azimuths and plotting off the wrong assumed position are also regular mistakes :( Not rushing any phase of the process seems to reduce the frequency of errors.

Good job on this round of stars !

A certain amount of error will just be the natural personal deviation from the mean. For me the max. expected deviation from the mean is plus or minus 0.5' moa and also comes into play when determining index error using the natural horizon as reference. This is one of the reasons I don't try to adjust out the last 0.5' moa of index error on the sextant horizon mirror.

Greg Rudzinski

From: Randall Morrow
Date: 20 Apr 2012 07:59
April 17/2012 Tax Day star sight results

Date 4/16/12 PM GPS 35* 19.5 N, 119*05.5 W
Body Time Hs (AH) Ho Hc (USNO) a
Procyon 8-46-37 99*14.4 49*36.4 49*37.7 1.7T
Sirius 8-48-26 47*33.0 23*44.2 23*43.6 0.6T
Rigel 8-52-25 27*16.0 13*34.1 13*33.4 0.7 A
Venus 8-56-13 50*54.2 25*25.5 25*24.6 0.9 T
Capella 8-57-23 78*2924 39*13.5 39*14.4 0.9 A
Alkaid 9-01-54 90*57.6 45*27.8 45*27.3 0.5 T
Arcturus 9-03-24 61*01.4 30*29.1 30*29.8 0.7 A
Elnath 9-06-31 67*03.0 33*30.0 33*28.5 1.5 T
Denebola 9-12-22 116*36.6 58*17.7 58*13.9 3.8 T
Saturn 9-14-11 47*16.6 23*36.1 23*37.5 1.4 A
Spica 9-15-34 47*25.2 23*40.4 23*42.2 1.8 A

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