NavList:

Frank, you asked : "Could you tell us how you made your estimate?"

(1) - Method used

(1.1) - Print the picture full format on a sheet of paper (about 21 cm * 27 cm). Assume that all picture angles are conformal.

(1.2) - Al Nair - Peacock distance :70.5 mm , Al Nair - Horizon distance : 130.3 mm , Peacock - Horizon distance : 64 mm

(1.3) - From Éphémérides Nautiques 1981, get Al Nair - Peacock unrefracted separation at 1,107' or 18.450°. Consider it has the same numerical value as the local refracted separation for Jan 1st, 2019.

Use it as a scaling factor at 0.2617° / mm to get Al Nair height at 34°06' and Peacock height at 16°45'

(1.4) - From exactly S13°00.0 - W 163°00.0' on Jan 1st, 2019 , Height of eye = 0 ft, Standard Refraction, get :

Al Nair at 34°06' at UT = 5h53m00s Azimuth 221.6°    Peacock at 16°45' at UT = 5h53m54s Azimuth 214.3°  while at that time the Sun is about 8° below the horizon in Azimuth 244.1° . Maybe the date could be refined here, but this is not our scope as you indicated.

(1.5) - From averaging both Al Nair and Peacock get approximate UT at 05h53m30s.

(2) - Error budget : Assuming angles to be measured at +/- 1° - which should make up for all previous approximations - UT is determined at about +/- 6 minutes of time.

(3) - Improving this method

(3.1) - Get a more accurate position (if you can, Frank, YES, publish it)

(3.2) - Get a better scaling factor, i.e. start from refracted altitudes of date.

(3.3) - Get a better feeling for DIP, i.e. assume HoE close to 15'

(3.4) - And - marginal effect most probably lost in the observation "noise" - use a non-standard Atmosphere, e.g. 1013.25 mb / 25°C

So, if you can indicate a better position, when I have time I will improve my first estimate as per the points here-above. It will be interesting to see the magnitude of this correction onto UT.

How does that sound ?

Kermit