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A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: Planet rising
From: Dave Weilacher
Date: 2002 Feb 3, 06:18 -0500
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.