NavList:

Jean
I commend your dedication.  I know when all things are considered I can’t aim better than to about two minutes of arc, so I tend to take a more pragmatic approach and calibrate directly from eye to star (see last paragraph).

Many people say the manual averaging system on their Hughes MKIX Bubble Sextant is broken.  I usually think the same myself until I work out again how to use it, which I need to do each time I take one of my MKIXs from its case.  Therefore I’ve made out the checklist below:

Getting ready:
1.  Wear watch on inside of left wrist.*
2.  Set ten degree slot and five degree increase mirror as required.
3.  Use fine adjusting knob to set fine counters to 0.00 or 5.00.
4.  With trigger pulled turn averager zeroing knob clockwise until averager counters read 0.00 or 5.00**, ***
5.  Release trigger and press six shot button so the shot window reads 0.

Making the observations:
6.  Turn fine knob until fine counters read Hc.
7.  Note the time.
8.  Centre the star and pull the trigger.
9.  With the trigger still pressed turn back the fine setting knob until the fine counters read 0.00 or 5.00****.  Only then release the trigger.

Remaining sights:
10.  Repeat 6, 8, &9 until all six sights are taken.
11.  Note the time.
12.  Note the average Hs.
13.  Calculate mid-time.

Notes:
*If you wear your watch on the inside of your left wrist, it’s lit up by a light fed though the right hand grip of the sextant for that purpose.
 **If you don’t pull the trigger, the averaging counters won’t set to zero.
***Funnily enough, with sextant 230/40, you pull the knob before turning it.  14908/40 has a slightly different inner to the knob and you have to push before turning for anything to happen.
****If you don’t keep the trigger pressed while the fine counters are set back to zero, the 1/6 increment of the previous sight isn’t retained by the averager counters.

Obviously, with an assistant, much of this rigmarole can be avoided.  When calibrating, I simple make the sight and shout “Now”.  MrsP presses pause on Frank Reeds GPS Anti-Spoof App, records the time and Frank’s Hs and I call my Hs, which she also notes.  Afterwards, we calculate the error of each sight and calculate the average.  DaveP