NavList:

Thomas K you wrote:  “I am following up on an Aug. 6 inquiry about moon altitude corrections using a bubble horizon. which are used or ignored.? the main correction includes s.d. which is ignored in artificial horizon calculations. how is it used? thomas k

[earlier post: "Bubble altitude corrections especially use of the main and parallax corrections for the moon? an example would be helpful. thank you"]”

I suspect that the reason you didn’t get many replies after 6^th August is that many air navigators regard the moonshots as their Bette Noir to be used only by masochists, the terminally short sighted, or those trying to impress their colleagues with a Sun Moon or a Sun Moon Venus fix.  If using a bubble or pendulous reference sextant, it ought to be simple.  The only corrections if you aren’t moving are index error, refraction, and P in A (parallax in altitude) taken from THE AIR ALMANAC.  I stress taken from THE AIR ALMANAC, because Nautical Almanacs sometimes try to be too helpful and produce total corrections assuming you’re using a marine sextant and shooting the Moon’s lower limb, so there might be a sneaky semi diameter stuck in there somewhere.  With an aircraft sextant you just stick the middle of the Moon in the middle of the bubble or graticule and shoot away.  You’ll find P in A at the bottom right of the Air Almanac daily page.  You enter the table with height observed (or calc it hardly matters) and read a value for P in A to be applied to height observed.  If I recall, it’s aways positive.  I’m afraid the Moon’s still below the horizon here now, it’s past my bedtime, and I’ve a busy few days ahead, but I’ll try and put an example together in a few days’ time.  DaveP