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 > > ------------------------------------------------------------------------- > Subscribe/Unsubscribe info, Frequently Asked Questions, SeeSat-L archive: > http://www.satobs.org/seesat/seesatindex.html > ------------------------------------------------------------------------- Subscribe/Unsubscribe info, Frequently Asked Questions, SeeSat-L archive: http://www.satobs.org/seesat/seesatindex.html
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