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Subject: Re: Time of planet rising
From: Herbert Prinz (hprinz@XXX.XXX)
Date: Sun Dec 09 2001 - 19:11:24 EST
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.
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