NavList:

Yes, Frank, I enjoyed seeing the nearly full Moon in the NW around 0800 on Tuesday morning. It was about ten Moon diameters above the horizon and almost exactly over the distant TV mast behind which the Sun sets on mid summer’s day. That fits in with the 5° tilt that you highlight.

This made me look more closely at similar unusual effects 7 days previously when the hyperactive Moon’s declination was around 0° and increasing at 6.5° per day. This high rate of increase resulted in consecutive Moon rises (just) less than 24 hours apart and, at the position chosen in the first attached Astron screenshot, two rises on the same UT day. The opposing Southern hemisphere location would show two Moon sets within 24 hours. What happened to the sailor’s “50 minutes later every day” adage?

Of more direct navigation interest, imagine taking Moon meridian passage sights with an accurate theodolite, recording the time of culmination and calculating your latitude and longitude. The first screenshot shows the moment of culmination, 06:19:44 with UL altitude of 31° 09.2’.  The second screenshot shows the need for a time correction of -7^m 45^s, a correction of S0° 1.1’ in latitude and a longitude correction of E1° 52.6’.  Perhaps using the Moon for meridian passage sights is not always a good idea. (I know the Moon’s UL was not quite illuminated at the example time, but I set UL to give the Moon rise times for the relevant location, time and atmosphere.)

Bill

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