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Thank you George! Here at last we have the crucial information about 
"parallatic retardation". That it might, if it is a factor, contribute ".05 
seconds of arc [or] 0.2 seconds of time." to the skilled observer's final 
calculation, which is still uncertain within one minute of time.

My confusion over 'lunar distance' here was not from misunderstanding the 
angular measurement used all along, but from the reference to never knowing 
what it was--since the angular measurement can "always" be known (with some 
inaccuracy, but that applies to everything measured) simply by measuring it.

One apparently can readily know the lunar distance, well enough that it 
accounts for an error (an error in position, which you may call an inaccuracy 
of observation or otherwise) on the order of one third of one percent. I was 
always taught that absent better information, anaglog instruments should be 
assumed to have an error of at least twice the width of the needle on their 
guage, allowing for parallax and whatnot.

If this whole discussion centers on an error that will at most be 0.00333 of 
the best possible result, I'll simply continue to use a fatter pencil to plot 
my location and be satisfied with the resulting circle of error, without 
accounting for parallax effects in any other way. I fail to see any practical 
use or application of them, although it is nice to understand that errors, 
inaccuracies, or whatever shortcomings are still inherent in the process.

   

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