A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
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:
Dec 24, 2017 moon-Aldabaran (far)
GMT of observation 00:05:54
Alt Cor -42.8'
Alt Cor 01.3'
>LDc 95°04.5' Cleared
>%Change -0.85 % difference Pre-cleared -> cleared
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
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