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Francis,

I've noticed a few errors in the calculations you attached in your message to David:

1. You are adding the index correction after dividing the AH altitude by two. The index correction should be added first.

2. For the Moon altitude, you divide 69°11' by two and get 35°35'30". This should be 34°35'30". (Actually, it should be 69°11.0' + 0.5' = 69°11.5' / 2 = 34°35'45".)

3. For the lunar distance, you add 36°29.5' + 0.5' + 0.24' and get 36°30.0'. This should be 36°30.24'. Also, a final result of 36°45.94' is not possible either way.

4. Using the NA Moon correction table, the main correction you cite (54.5') is appropriate for an H_a of 38°40', not 35°36'. I'm not sure where you got the second correction from.*

I'm not familiar with the particular clearing method you used, so I didn't go any farther.

* I find the bubble sextant instructions in the NA quite unclear. If I understand them correctly, the correction should be something like:

H_a: 34°35.7'; HP: 58.4'

Main Correction: +56.7'

Lower Limb: 56.7' + 5.9' = 62.6'

Upper Limb: 56.7' + 4.1'  = 60.8'

Average: (62.6' + 60.8') / 2 = 61.7'

34°35.7' + 61.7' - 15' = 35°22.4'

This is close to the figure I arrived at when calculating refraction and parallax directly. (35°22.3')

Regards,

Sean C.