NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: The *&^%$#@ Moon
From: Peter Fogg
Date: 2006 Aug 18, 14:22 -0500
From: Peter Fogg
Date: 2006 Aug 18, 14:22 -0500
Clive wrote:
"Take about 10 or more sights of the moon as close together as possible in time and to plot the result. If this plot is a straight line, you could compare the slope of the plot with the rate of change of the Moons altitude."
This is a good idea in any case. The slope is the fact of the moon's apparent rise or fall that can be compared with your range of observations (above and below that line). The probable result is that you will choose a point along the slope that best fits the obs and use its indicated altitude and time; which may well be more accurate than any of the actual obs. The time period of obs should be not much greater than 5 minutes, as the slope, drawn as straight line, is actually an arc. (When this was discussed on the old list earlier it was proposed that the deviation in some extreme case was less than 1 minute of arc over 5 minutes. The improvement in accuracy is typically greater than this.)
This won't help if the fault is systematic.
Robert wrote:
"Is this all in my head??"
I don't know, but its in mine too. Have noticed a similar propensity for the moon to give unreliable results, but had put it down to some of the factors already mentioned, in particular errors due to the extra steps of sight reduction, without examining the question closely.
Howl ..to the moon ...
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"Take about 10 or more sights of the moon as close together as possible in time and to plot the result. If this plot is a straight line, you could compare the slope of the plot with the rate of change of the Moons altitude."
This is a good idea in any case. The slope is the fact of the moon's apparent rise or fall that can be compared with your range of observations (above and below that line). The probable result is that you will choose a point along the slope that best fits the obs and use its indicated altitude and time; which may well be more accurate than any of the actual obs. The time period of obs should be not much greater than 5 minutes, as the slope, drawn as straight line, is actually an arc. (When this was discussed on the old list earlier it was proposed that the deviation in some extreme case was less than 1 minute of arc over 5 minutes. The improvement in accuracy is typically greater than this.)
This won't help if the fault is systematic.
Robert wrote:
"Is this all in my head??"
I don't know, but its in mine too. Have noticed a similar propensity for the moon to give unreliable results, but had put it down to some of the factors already mentioned, in particular errors due to the extra steps of sight reduction, without examining the question closely.
Howl ..to the moon ...
--~--~---------~--~----~------------~-------~--~----~
To post to this group, send email to NavList@fer3.com
To , send email to NavList-@fer3.com
-~----------~----~----~----~------~----~------~--~---
