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Subject: Re: Time of planet rising - formula
From: Noyce, Bill (William.Noyce@XXX.XXX)
Date: Mon Dec 10 2001 - 10:48:13 EST
> How can I determine what time a planet will rise?
A simple formula will give the LHA at which a body's
computed altitude (Hc) is zero, given the body's
declination and your latitude:
cos(LHA) = tan(dec)*tan(Lat)
This ignores refraction and dip (height of eye).
Refraction at the horizon is about 34', but somewhat
variable; the planet will actually appear to rise or
set when its Hc is about 34' below the horizon. Unless
your atitude is very high, you can approximate the
actual rise/set time by adding refraction and dip to
the LHA. Then apply that angle (east for rising, west
for setting) to your longitude to get GHA, and use the
almanac to find the time at which that GHA occurs.
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