Air Navigation by Bubble Sextant

[Tom]

Update on progress.

I bought two Mark IXA bubble sextants, and with help of Bill Morris’s excellent guide I have got one working save for the averager. I have not checked the index error yet.

However yesterday the sun appeared briefly and I got a sight.

I plotted the ensuing LOP and the closest I was to that position line was 70ish nm. 

Could I just check a couple of things.

I used the air almanac, corrected for atmospheric refraction, but did not use LL or UL as I put the sun in the bubble. Is this correct?

Can anyone explain how the averager on a Mark IXA works, i.e. the principle?

Thanks

Tom