Navigator wrote:

... "is the period from rise to set at a
fixed location constant?"

No. See other post.


... Is it constant at a fixed location on the same day
each year? If not why?

No, because the number of lunar months in a year is not a whole number. Even
if it were, the period would likely still vary year-on-year due to the
nutation period of the moon's orbit, which causes a variation in the
azimuths of the northern and southern standstills (and the rise/set points
in between).


--
Wally
www.forthsailing.com
www.wally.myby.co.uk