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Subject: Re: Planet rising
From: Hal Mueller (hal@XXX.XXX)
Date: Sat Feb 02 2002 - 03:02:17 EST
At 12:34 AM -0500 2/2/02, David Weilacher wrote:
>Okay. I definitely mis-stated my question.
>
>How do I determine time and azimuth of a planet rise, given:
>
>My DR position
>A nautical almanac.
>H.O. 229 sight reduction tables.
>Paper & pencil.
>No calculator.
I believe you'll have to guess, and then interpolate. That is, try
to guess two times, one when the planet is definitely up and one when
it is definitely down. Look up/compute the planet's elevation at
those times. Plot the time on one axis of some homemade graph paper,
the planet's elevation on the other axis. Connect those two points,
read your graph, and see when the planet's elevation crosses zero.
Now use that time to enter the Nautical Almanac again and get a new,
exact elevation for that time. If that's close enough to zero,
you're done. Otherwise choose another time 1/2 hour or so away from
your most recent guess, and repeat the above procedure. You can do
this as many times as you like, refining your estimate at each pass.
Hal
---- Hal Mueller hal@XXX.XXX Mobile Geographics LLC http://www.mobilegeographics.com/ Seattle, Washington (206) 297-9575 MapTap public test now underway! http://www.mobilegeographics.com/maptap/
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