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Re: Time of planet rising - formula
From: Bill Noyce
Date: 2001 Dec 10, 8:48 AM
From: Bill Noyce
Date: 2001 Dec 10, 8:48 AM
> 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.