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A Question About Lunar Standstills

-- Brian | November 22, 2020

Question:

Hi Jeff,

Apologies in advance if this appears to be a stupid question (or couple of inter-relational stupid questions), but I have only a rudimentary understanding of the subject.
On the wikipedia page for lunar standstills @ https://en.wikipedia.org/wiki/Lunar_standstill, there is listing for the ‘Apparent position of the moon during standstill’. The listing has 2 tables indicating the ‘Azimuth of full moon on horizon’ given for 2 latitudes and epoch at minor, midway, major.

Q1. I am trying to replicate this within Stellarium, but I am struggling with how to resolve this to actual dates. Could you give me some idea of how I might go about this. My suspicion is I can achieve this using jpl horizons but have no experience of using it in this way.

Q2. A couple of the azimuths listed on the table seem to have remarkably geometric values, i.e. 45° and 135°. Is this entirely fortuitous, perhaps based on the example latitudes ? Why these exact natural divisions of 360° ?

Any info, or referral you can give me is much appreciated,

Thanks for your patience,

regards

-- Brian

Answer:

For your first question, I believe that the azimuth values listed are geographic azimuth values, where azimuth 0 is true north and azimuth 270 is west. To translate this to Stellarium I believe that all you need to do is to set the geographic azimuth to the values provided at the specified latitude of 55 degrees north or south. As for your second question, I can’t think of any physical reason why the azimuth values would be integer multiples of 45 degrees.

-- Jeff Mangum

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