Yesterday morning, and given the emerging daylight conditions I watched from my A340 cocckpit the occulation of a very faint celestial body by the Moon as follows :
Date Sep 18th, 2017 Time : UTC = 02h51m30s as read from the GPS clock
9H-JAI Position : 29°11'4N - 029°58'0E altitude : FL 410 i.e. 41,000 feet
Note : the biggest inaccuracy here is the time check : +/- 30 seconds of time accuracy - since the aircraft clock only displays integer minutes of time, and I had no time to dig into the FMS to recover the exact GPS Time.
I observed with naked eyes a celestial body disappear between the lower bright Moon Limb.
1 - Which Body ? Star or Planet ?
2 - Assuming that all data are exact, how accurate was my naked eye observation at an altitude of 41,000 feet ?
3 - Assuming that all data are exact, how accurate would have been my naked eye observation, assuming that I would have observed it from ground level at the same UTC and Position. NOTE : This you should be able to easily solve - although refraction at ground level is much more important - provided this occulted Body is one of the Frank's Lunar Computer published ones.
4 - Lady Venus was very bright and a few ° over Lady Moon's upper and dark limb. But .. I also spotted 2 celestial bodies about 8° to 10° below the Moon. One of them was brighter (probably Mercury ?) and the second one was rather faint about 2° above the brighter one, both seeming very close from the ecliptic. What are these Bodies ? My initial guess (no time to check yet) would be that the occulted body (the faintest of all three) was either a rather bright ecliptic star or Planet Mars, and that both bodies below the Moon might have been most probably Mercury (lower and brighter) and Saturn (higher and fainter).
Note : Given the relative position of Venus and the Moon, there should have been a Venus occultation a few hours before my observation and visible somwhere on Earth. This also I have not crosschecked yet.
Antoine M. "Kermit" Couëtte