posted on Aug, 5 2011 @ 09:58 AM
I should add Telling time by the stars is not really very useful.... but if ya want to be really hard core...
Really this is way crazy Comp-lu-ma-kated... but I know someone is bound to ask...
Anyway, here is how I do it. This is just a quick overview; you will have to fill in many details on your own. Also note that tradeoffs have been made
between convenience and accuracy: there are simpler methods that are grossly inaccurate, and more-accurate methods that are more complex (using
equatorial rather than circumpolar stars).
1. Memorize four landmarks (skymarks?) ◦ The 0-hour circle. This is marked by Beta Cassiopeiae (Caph) which is the star at the bright end of the
famous W in the constellation Cassiopeia, i.e. the end with the acute angle. Continuing along the 0-hour circle, we come to Alpha Andromedae
(Alpheratz) and Gamma Pegasi (Algenib) which together constitute the trailing (eastern) edge of the Great Square – hard to miss.
◦The 6-hour circle. This is marked by Delta Aurigae, Beta Aurigae (Menkalinan), and Theta Aurigae.
◦The 12-hour circle. This is marked by point halfway between Delta and Gamma Ursae Majoris, the two non-pointer stars in the bowl of the Big
Dipper. (The pointer stars are excellent markers for the 11-hour circle.)
◦The 18-hour circle. This is marked by Chi, Phi, Xi, and Gamma Draconis, i.e. the hind feet, chin, and nose (Eltanin) of the Dragon.
Also remember that the 12-hour circle is the continuation of the 0-hour circle, and that the 18-hour circle is the continuation of the 6-hour
2.Remember that the 12-hour circle is overhead at midnight at the spring equinox. The 18-hour circle is overhead 6 hours later, and/or 3 months later
in the year. And so forth. This gives you four “primary” reference pictures, where one of these four circles is overhead.
3.You can then construct four “secondary” reference pictures, halfway between the primaries. These correspond to the situation where the primary
circles form a giant V shape that is symmetrical with respect to the vertical. Do not try to judge the angle that the circles form relative to
horizontal, because the perception of horizontal is distorted by the spherical geometry. The perception of vertical is OK, and the perception of
symmetry is OK. Anything else you need can be judged by interpolation between the symmetrical (secondary) picture and the vertical (primary)
4.As you face north, the great clock in the sky rotates counterclockwise.1,2 It moves counterclockwise as you get later in the night or later in the
year. The time-of-year contribution is 2 hours per month, or half an hour per week, or four minutes per day.
5.Therefore: Suppose it is March 22nd. If you see the 12-hour circle is past vertical, 1/3rd of the way to the symmetrical V position, it must be
1:00 AM. If it is two weeks later in the year, the same picture is 12:00 midnight (standard time); the advancement is explained by being later in the
year, not later at night.
6.Correct for daylight savings time. If DST is in effect, official time is one hour later than star time.
7.Correct for longitude. ◦To a rough first approximation, time zones are 1 hour wide, and the standard time in each zone more-or-less corresponds
to the mean solar time at the middle of the zone. Therefore, roughly speaking, if you are near the edge of a zone, standard time could be offset by
half an hour from the local mean solar time.
◦In reality, things are much more complicated than that. Time zone boundaries follow political boundaries, not the ideal theoretical lines of
longitude. Useful diagrams can be found in reference 1. You can easily find places (such as western Spain) where the standard time is offset by more
than 1.5 hours from the local mean solar time. That is, the zone extends more than 1.5 hours from where the middle of the zone “should” ideally
If you are west of the nominal midline of your time zone, official time is later than star time. By the same token, if you are east of the midline,
official time is earlier than star time.