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Subject: Re: Planet rising
From: David Weilacher (daveweilacher@XXX.XXX)
Date: Sun Feb 03 2002 - 06:18:46 EST
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 <wepster@XXX.XXX>
> To: <NAVIGATION-L@XXX.XXX>
> 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@XXX.XXX
> tel +31 30 253 1186
> Mathematisch Instituut
> Universiteit Utrecht
> PO Box 80.010
> 3508 TA Utrecht
> The Netherlands
> ===========================================================
--- David Weilacher
--- daveweilacher@XXX.XXX
--- EarthLink: The #1 provider of the Real Internet.
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