NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: Time of planet rising
From: Herbert Prinz
Date: 2001 Dec 09, 5:11 PM
From: Herbert Prinz
Date: 2001 Dec 09, 5:11 PM
Rising (and setting) times for the four navigational planets can be found from the almanac alone without the use of a calculator with an accuracy better than 5 minutes, if the declination of the planet is within 23.5 deg. The times of meridian transits of the planets are tabulated on the bottom left page in the daily pages. The interval between rising time and meridian transit can be obtained from the corresponding entries for the sun on a date where the declination of the sun is near that of the planet in question. Subtract a minute or two for the rising time of the semidiameter of the sun, but ignore v-correction, which never amounts to more than a minute. Effect of refraction is incorporated in the sunrise table. If the declination is outside the +/- 23.5 degree band, we have to resort to the star finder. We need the red template and the blue one closest to our latitude. Superimposing the red one over the other, turn it until the blue horizon line (outmost ellipse) intersects the red ray labeled 0 deg (at the edge of the window) exactly at the mark for the given latitude of the planet. Now, read the hour angle on the red disk at the blue ray marked 180 deg (the only one protruding all the way out). (Unfortunately, on the 2102-D, the division on the red template is only in steps of 10 deg, so you have to estimate the degree, or hold the white disk underneath). Divide the hour angle by 15 to get the time interval between rise and culmination. Allow for refraction by adding 2 to 4 minutes, dependent on rising angle. The error resulting from the lack of a suitable template for the exact latitude may amount to several minutes. Herbert Prinz (from 1368950/-4603950/4182550 ECEF) David Weilacher wrote: > How can I determine what time a planet will rise? > > Both with and without using Star Finder 2102-D or equivalent.