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#48 Moon Data Problems
The data for moon rise and set times appear to be in error when
compared to US Naval Observatory ephemeris. Also, for a date of
October 2, 2004 when changing between 4:10PM and 4:11PM the
rise time for the moon changes from 8:30PM to 9:03PM. Lat/long
inputs are 37d9m N and 76d23m W and I am manually adjusting
for daylight savings time. I have version 2.5.1 and version 4.1 of
the Palm OS.
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Please note the "-" and "+" sign after the rise/set time, which
tell you that this time is for previous resp. next day. In astroinfo
the data is displayed so that rise time < set time, which means
that often one of the times has to fall on the next or previous
day. It chooses the rise/set time so that the transit time is
nearest to the current time, so it may depend on the current
minute.
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The errors in rise/set time are typically less than 1 hour and are not
issues with the day. I'm not sure I understand your comment about
AstroInfo choosing the rise/set time so that the transit time is nearest
the current time. Shouldn't the transit time for a given date and location
be constant and not a function of the current time?
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I tried it with several different days for your location and
checked with the times given me ba US Naval Observatory at
http://aa.usno.navy.mil/data/docs/RS_OneYear_noJS.html
The rise/set times in astroinfo were always at most 1 minute
away from the times calculated by the above web page.
Regarding the transit times: There is one transit before the
current time and one transit after. Astroinfo chooses the one
that is nearer. So if moon transit is shortly after midnight and it
is 11 pm, it chooses the transit that happens in few hours
instead of the transit that happened more than 20 hours ago
but on the same day.
So for 4:10 PM it shows the previous transit
8:30PM (-) to 11:10AM
and at 4:11PM it show the next transit
9:03PM to 12:12PM(+)
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Looked at the data/display more closely. I now understand what you
were saying about the dates. Thanks for your patience with my
comments.