NavList:

I asked if there was ever an occasion when three one or two-minute astro shots four minutes apart shouldn’t be averaged.  The answer is yes and no.  Yes, if the middle shot coincides with meridian passage, because a perfect middle shot is bound to be higher than perfect shots four minutes either side.  No, because four minutes either side of meridian passage the change in Hc is tiny compared to the likely advantage of averaging three real shots compared to a single real shot.
E.g. Monday 24^th February 2025 Time 12:13:30UT LHA Sun 000;5.7’
                                                53N 0E/W                                   52S 0E/W
12h:09’:30”UT                         Hc=27°44.0’                               Hc=46°15.4’
12h:13’30”UT                          Hc=27°44.3’                               Hc=46°15.7’
12h:17’30”UT                          Hc=27°44.0’                               Hc=46°15.1’
Average                                  Hc=27°44.1’   0.2’ low                Hc=46°15.4’  0.3’ low
Hc's calculated using 'Navigator'.  DaveP