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> *From: *Martin Caminos
> *Date: *2024 Jun 9, 19:58 -0700
>
> Earlier today, I took the advantage of the clear skies at Cusco to shoot
> some lunars with the Mark II sextant I brought with me.


Data from the screen shot:

2024-06-10 00:03:50 UTC (on that date IERS Bulletin A says UT1-UTC < 0.1 s)

N 13°31.40' W 071°55.00' +3400 m

12 C 668 mb

29 11.5 + (-1.5 IC) = 29 10.0 Regulus to far limb

The 668 mb air pressure is apparently "station pressure," i.e., the
pressure at the observer. However, my software needs altimeter setting
so I used the nominal value 1013 mb. At 3400 meters altitude, the
program says station pressure = 666 mb.

It calculates 29°09.17' lunar distance, 0.83' less than the 29°10.00'
observation.

If I use 668 mb as altimeter setting, station pressure at 3400 m is 439
mb, much too low. At that pressure my computed lunar distance increases
from 29°09.17' to 29°09.64', which is closer to the observation.

--
Paul Hirose
sofajpl.com

   

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