Astronomy/Moon's travel


I live in NJ USA which is about 41 degrees above the equator.  I usually see the moon in the southern sky.  Based on what I would call the moon's "Tropic of Cancer", does the moon ever pass directly over NJ?  I raise this question because the moon DID appear to be in my West Northwest sky the other evening.  I guess your most concise answer would be for you to state the degrees above the equator of the moon's Tropic of Cancer (if a constant), and if different a similar degree below the equator for my friends in Australia.  Thank you in advance. Ken Tekel, retired math teacher on Memorial Day (also mourning the loss of Mathematics and Princeton's great John Nash)

The furthest north the Moon can ever get is about 28 1/2 degrees north of the Celestial Equator, so it can never pass overhead at your location (which would require it to be 41 degrees north of the Celestial Equator). But at such times it can rise over 30 degrees north of east and set over 30 degrees north, partly due to the 28 1/2 degree north declination, and partly due to the tilt of its path relative to the horizon at your latitude (which can be as much as 41 degrees; but it would take a little spherical trigonometry to figure out the exact angle on any given day, as it would change as the Moon moves around its orbit). As a result, for the last few hours before it sets it could be somewhere north of west at your location. If you were far enough north (90 minus the Moon's declination and further north) the Moon could be up all day when at its northernmost point, and even pass due north at its lowest point, just like the Sun could be up all day if you were north of the Arctic Circle.

Because of an 18-year rotation of the orbit of the Moon relative to the background stars, the Moon's furthest northern point varies from 18 1/2 to 28 1/2 degrees. Right now the value is close the minimum value of 18 1/2 degrees, but in 9 years it will be close to the maximum value of 28 1/2 degrees, so at that time you'll be able to see the Moon in the west northwest for a considerably longer period before it goes down, whereas right now it would only be north of west for an hour or three.

(Addendum: Everything would be the same for observers at 41 degrees south latitude, but with 'north' replaced by 'south'.)


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Courtney Seligman


I can answer almost any question about astronomy and related sciences, such as physics and geology. I will not answer questions about astrology and similar pseudo-scientific rubbish.


I have been a professor of astronomy for over 40 years, and am working on an online text/encyclopedia of astronomy, and an online catalog of NGC/IC objects.

Astronomical Journal, Publications of the Astronomical Society of the Pacific (too long ago to be really relevant, but you could search for Courtney Seligman on Google Scholar)

I received a BA in astronomy and physics and a MA in astronomy, both from UCLA. I was working on my doctoral dissertation when I started teaching, and discovered that I preferred teaching to research.

Awards and Honors
(too long ago to be relevant, but Phi Beta Kappa and Sigma Xi still keep trying to get me to become a paying member)

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