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    Re: Planet rising
    From: Dave Weilacher
    Date: 2002 Feb 3, 06:18 -0500

    This has proved to be a simple, practical, therefore highly El-ee-gant
    solution to my query.  Thank you.
    It produces an answer to within 3 minutes of the answer key to a test
    question.  Considering the nature of the problem, I'd be hard pressed to
    call a 3 minute difference wrong.
    For instance, can you actually see a planet right on the horizon at civil
    twilight?  Should you allow some time; perhaps 3 minutes:-), for it to get
    high enough to distinguish?
    Is the atmospheric distortion of the sun and a planet the same?
    Are you more or less right if you wiggle your projected DR around to get a
    more precise LMT computation?
    > [Original Message]
    > From: Steven Wepster 
    > To: 
     > Date: 2/2/2002 4:16:53 PM
    > Subject: Re: [NAV-L] Planet rising
    > Dear David,
    > If you are willing to use HO249 instead, I propose the following
    > method. It's not exact to the minute.
    > Look up the declination of the planet for the date you're interested
    > in and round to the nearest degree. Open HO249 on the page corresponding
    > to your latitude (whole degrees) and planet's declination, paying
    > attention to 'SAME' or "CONTRARY' signs for those values. Select the
    > right column for declination; in this column go up or down until
    > you find altitude Hc = -0;34 or as close to it as you can. On this line
    > you find two LHA's: one on the right and one to the left of the table.
    > Take out those LHA's and add (or subtract, depending on E or W) your
    > longitude. Now you have two GHA's which correspond approximately to the
    > GHA of the planet at rise and set. Look up those GHA's on the daily page
    > in the almanac under your planet to get the times of rise and and set. For
    > this you will have to do reverse interpolation.
    > If you insist on using HO229, you can follow essentially the same method,
    > but it is a lot more clumsy because HO229 has one LHA per page, so you
    > have to flip pages back and forth until you find Hc ~ -0;34 in the right
    > row and column.
    > Success,
    > _Steven.
    > -----------------------------------------------------------
    > Steven Wepster                          wepster@math.uu.nl
    >                                         tel +31 30 253 1186
    > Mathematisch Instituut
    > Universiteit Utrecht
    > PO Box 80.010
    > 3508 TA Utrecht
    > The Netherlands
    > ===========================================================
    --- David Weilacher
    --- daveweilacher@earthlink.net
    --- EarthLink: The #1 provider of the Real Internet.

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