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    Re: Bubble horizon altitude corrections
    From: David Pike
    Date: 2024 Sep 23, 13:49 -0700

    Thomas K you wrote:  “… or carry around 738 pages of the air almanac to use one number ?”

    The good news is you don’t need to.  You can download the Air Almanac online at 100% discount and store it on your phone, laptop, or PC courtesy of the USNO.   Try going to https://aa.usno.navy.mil/publications/aira .  If you have VPN on your device, you might have to temporarily turn it off before the USNO will connect with you.  I got you a set of ye olde bubble sextant Moonshot values to work with.  Last Wednesday Sep 18th 2024.  I took out my favourite Hughes MkIXBM No 4077 of 1942.  Surprisingly, it still had a perfect sized bubble plus two C batteries left in from the last time I used it about a year ago.  Naughty me, you’re supposed to remove bubble and batteries after use.  Initially, I couldn’t see the Moon, but after I’d removed six of the seven shades, also left in from last use, I got quite a useable Moon/bubble combination.  I had intended to plot the whole thing using the Nautical Almanac, just for fun, but when I got as far my first page of notes and realised it was going to tax the powers of a professor of Astro Physics from MIT, I decided to leave it until I had more time.  Meantime you ought to try it using the Air Almanac.  I’ve photographed the relevant pages for you.  An air Navigator would try to shoot on the ten minutes to save time to arc calculation, but by the time I’d got the sextant set up it was 22hrs 24minutes 41seconds.  I’ve finished my calculations and PL, but I’ll keep it until I see yours.  My sextant measured 32degrees 19minutes.  Frank Reeds GPS Spoof was saying it should be 32degrees 17minutes, so it must have been a reasonable shot. DaveP

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