NavList:

From: Gary LaPook <garylapook@pacbell.net>
Subject: [NavList] Moon observations in flight
To: "Navlist" <NavList@fer3.com>
Date: Thursday, June 28, 2012, 1:25 PM

I went flying on Tuesday and one of my purposes was to take some celestial observations. I chose the day so that the sun and moon would be properly placed to allow getting a fix, unfortunately I didn't allow for the sun being so high, 79°, and the overhead prevented getting any sun shots. I did take two observations of the moon, one each with the MA-2 and the A-7 bubble octants. I took ten shots with the A-7 and the average altitude was 17°54' which produced an intercept of 5.7 NM away. I did a two minute average with the MA-2 and the altitude was 20° 00' which produced an intercept of 6.4 NM toward. Actually, to not exceed the accuracy of my data, I should say that the intercepts were each 6 NM. I'm pretty happy with these results because keeping the plane in steady flight is critical for accuracy and I was flying solo without an autopilot so I had to level the wings, line up the moon in the octant for a few seconds, check to see if the wings were still level and straighten them up if necessary, observe the moon for a few more seconds, repeat... plus there is always the problem using the moon when it is not full since you have to estimate where the center of the moon should be and place that in the center of the octant's bubble. So 6 NM accuracy with all those impediments which is within the expected 7 NM uncertainty of bubble octant observations taken in flight was quite satisfying.  See the attached plots. The red line is the track of my plane as recorded by my GPS. gl