A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
From: Peter Fogg
Date: 2008 Nov 16, 20:19 +1100
Basically agree. Using all of the sights I derive, at the time of the first, a probable position of:
N14d 15.3' E142d 53.2'. Have allowed for the ship's movement while the upper limb of the moon is being observed. As Greg Rudzinski points out, the ship is steaming at 080d, while the position line extends towards 069d; fairly similar.
Have plotted these sights and compared them with the calculated slope. They are evidently very consistently good observations, showing little spread. Since the apparent movement of the moon (or any celestial body) as it rises/falls is an arc, extending the time-spread of the multiple sights beyond about 5 minutes, as here, could lead to those at either end being less reliable.
Adopting 19h 08m 00s and 65d 54' leads to an azimuth of 159.1d and an intercept of T0.6, which may be a slight improvement on the sight taken at close to that time, #4: 19h 08m 06s, Hs 65d 55.0' ? At any rate, plotting them reveals that there are none (excepting perhaps those at either end, for the reason above) which need be discarded. In this case an average should give a good result.
Jeremy posted the problem in NavList 5416 on 13 Jun 08; mind his corrections which followed soon after.
I was browsing through the exercises that Jeremy kindly posted on the list back in June. Today I was working out exercise 14 Multi-moon LOP's and I've seen there was no solution posted (if I'm not wrong), so here's mine.
I've averaged the sights and obtained a Hs of 65 deg 59,8' at 09 09 14 UTC (or 19 09 14 ZT). This yields to a calculated altitude of 65 deg 55,5' (I use the haversine method and Norie's tables 'cause I like working the old way) and to an intercept of 1.3 NM forward. The azimut is 160 deg. Moving back the LOP to 19 00 00 ZT and assuming the intersection between this LOP and the course made good as the most probable position I got a fix at 14 deg 17,0' N 142 deg 58,5' E.
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