NavList:

Joe Plazak you said:  "With this schedule, the 3-minute early and 3-minute late shots have the same magnitude of motion but an opposite sign".

Joe
it's called a 'Sandwich Fix', or for one body alone 'a Sandwich PL'.  In the V force something very similar was our bread and butter except our Nav-Plotters (the blokes with the pencil and the plotting chart) did it all on their chart.  Some corrections were taken care of before the Ho stage and others by moving the assumed position.  We only used two minutes total between one-minute shots, i.e. 30secs, 60secs, 30 secs.  There was just time to call out Hs and the heading check and rewind the sextant (very easy to forget and rewind before calling the Hs).  In the Vulcan you could even use two minutes between shots for a two-star sandwich fix if you took a second sextant with you, because the Vulcan had a port and a starboard sextant mount.  You set both sextants up and found both stars before you started.  Then you just stepped across the cabin between stars taking care not to fall down the hole above the entrance door/escape hatch or step on the 6^th or 7^th crew member if you carried one.

E.g. seven shot two-star sandwich fix for a fix-time of 2200hrs.
Mid times of seven one-minute shots

2154     2156     2158    2200    2202    2204     2206

Star A, Star A, Star B, Star B, Star B, Star A, Star A.
Start-times 30 seconds before mid-times.  Total shooting time 13 minutes.  Well, it gave you something to do.  DaveP