NavList:

Hello, Sergei!

Frank’s values are correct. Your assumption that he averages the altitudes of the Moon is wrong. Frank interpolates to get the Moon altitude at the moment he took lunar distance. Look at this time scale:

20:09:51 — the first Moon’s altitude

20:16:37 — Lunar distance measurement

20:17:57 — the second Moon’s altitude.

As you can see the second Moon’s altitude is closer to the time of lunar measurement than first one. Therefore this is not good case to average the altitudes of the Moon. The best way in such a situation is to use linear interpolation to get correct altitude. And this is excactly what Frank did.

You calculated Moons average altitude 46° 30,3’. But interpolated altitude will be 46° 59,5’. Then Frank uses historicaly widely used simplified correction for dip and SD (-20’ for upper limb). And he gets 46° 59,5-20’=46° 39,5’.

This is an apparent altitude of the center of the Moon. Therefore you enter the Moon correction table with this value and get first part of correction: 49,3’. Then you enter other table and get out second part of correction(average value between upper limb and lower limb for HP=54,7’) : about 2,3’. According to the instructions of the table you should sum these two corrections and then substract 15’. And you get: 49,3’+2,3’-15’=36,6’.   Frank’s value is 36,5', but this small difference is due to the interpolation between tabulated second part values.  

Modris Fersters