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Re: A lunar in 1845
From: Ed Popko
Date: 2019 Jan 4, 05:57 -0800

Frank, I need some help with your Halloween: Lunars: altitude accuracy and the 90 degree miracle you referenced. In rerunning an old lunar with a distance near 90 degrees, I get strange results. Below is the best lunar I have shot with an LD near 90 degrees. After clearing etc. it resulted in a GMT 16 seconds fast from the actual time taken. I got lucky.

Below is my Moon-Aldebaran data. Where I have trouble is retrofitting this sight in the altitude accuracy equations to see how little influence the moon's altitude would have had though I did take altitudes for this shot. Your web calculator did it for me. I'm just curious to see what altitude leeway I would have had.

Any help appreciated. My guess is it is a units problem and also that the moon accuracty equation goes to infinity as it approaches an LD of 90 degrees.

My best moon-Aldebaran lunar with a LD near 90 degrees using the Reed web calculator:

KP=28°41.1'N 082°18.2'W
Dec 24, 2017 moon-Aldabaran (far)
GMT of observation 00:05:54

Moon
   HaMoon    37°50.1'
   Alt Cor     -42.8'
Body
   HaBody     36°10.7'
   Alt Cor       01.3'
LDa         95°53.6'

>HP            55.19'

>LDc        95°04.5' Cleared
>%Change       -0.85 % difference Pre-cleared -> cleared
>delZcos       -0.706
>delZ         136.2°

GMT from Lunar Observation
00:00:00 95°07.7' Almanac bracket
00:06:15 95°04.5   Computed time from LDc
03:00:00 93°35.6' Almanac bracket

GMT Summary
--------------------
LDo         00:05:54 Actual GMT of observation
LDc         00:06:15 Calculation GMT from LD observation
Difference 00:00:21 LD calculated GMT was fast 21 seconds

Accuracy Required minutes of arc
Moon: ? -86 <---------------------------------- PROBLEM HERE
Body: 7'

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