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I duplicated the results of Modris Fersters with Lunar 4.4 (DE441
ephemeris).

time
2023-04-02 18:40:00.00 UT1
2023-04-02 18:41:09.48 TT
+1m09.48s delta T

position
  24°00.00' +56°00.00'  east lon, north lat
0.0 meters (0 feet) above ellipsoid

atmosphere
10.0 C (50.0 F) at observer
1010.0 mb (29.83″ Hg) air pressure
50.0% relative humidity

Moon
  44°11.89' computed unrefracted center altitude
     15.02' unrefracted semidiameter
      0.98' refraction
  44°27.90' apparent upper limb altitude
148°17.17' predicted azimuth

Venus
  16°52.49' computed unrefracted center altitude
      3.14' refraction
  16°55.63' apparent center altitude
278°45.19' predicted azimuth

My program recommends Moon upper limb and Venus far limb. It also has a
"center of light" option. But in this case, Venus phase angle is 58°, so
I don't think there's much error if observe Venus center and ignore
phase. The easy way is to select "center" for the Venus distance limb
(in the program main window). Then the output omits a correction for
Venus SD:

topocentric apparent Moon to Venus angle:
104°03.44' center to center, unrefracted
      3.25' refraction
104°00.19' center to center, refracted
    -15.02' Moon near limb refracted SD
103°45.17' computed Moon to Venus

The last line is identical to his value. But is it correct? You can get
azimuth, altitude, and angular diameter from the JPL Horizons online
ephemeris. (Does not give semidiameter.) Apply refraction to the
altitudes, then compute separation angle. Subtract Moon SD. (Lunar 4.4
says refraction has no effect on SD at 0.01' precision.)

https://ssd.jpl.nasa.gov/horizons/app.html#/

Careful - observer coordinate order is longitude, latitude, height.

There is an option to apply standard refraction, but I have never used it.

I would investigate this myself, but it's time to go to bed.

--
Paul Hirose
sofajpl.com

   

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