Re: Astronomical Quiz difia

From: Tim Rogers (timrogers@charter.net)
Date: Tue Apr 19 2005 - 21:08:24 EDT

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```Just for clarification, would this be true for any location on the planet?
When you say "when observed from directly below on the earth's surface," do
you mean *just* below the earth's surface (centimeters or inches?)

Tim Rogers
Sugar Hill, GA  USA

----- Original Message -----
From: "Jeff Umbarger" <jumbarger2000@yahoo.com>
To: <SeeSat-L@satobs.org>
Sent: Tuesday, April 19, 2005 7:19 PM
Subject: OT: Astronomical Quiz difia

> Hey All,
>     So, watching satellites the other night I came up
> a with an idea that I believe is correct, but I want
> to bounce if off others in the group to see if I'm on
> the right path. There is a point in the stellar field
> (that is described with coordinates Right Ascension
> and Declination), that when observed from directly
> below on the earth's surface, can never be seen in
> complete darkness. You can either name the RA and Dec
> or the name of the constellation. Please respond back
> to me and not to the group. I'll post the answer if
> enough folks are interested.
>     And now a slightly more on thread notion: I
> learned of a formula that tells when an observers
> Civil Twilight (when the Sun is 6 degrees below the
> horizon) is shortest during the year (when Civil
> Twilight follows Sunset in the shortest amount of
> time) based on the observer's latitude. The formula
> is:
> The date in March = March 21 - 1.0146 *
> arcsin(0.1427*sin(theta))
>
>     where theta = the observer's latitude.
>
> This, of course, is the shortest visual satellite
> observing night of the year - on average. This formula
> came from a magazine called The Bent, put out by Tau
> Beta Pi - an engineering honor society.
>
>     Regards,
>          Jeff Umbarger
>          Plano, TX USA
>
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