Sidereal Clock
(ver 2.0.1)
Abandoned Freeware


This is the free version of Sidereal Clock, which
is a very useful clock for Astronomers.  Remember 
that you need to configure it before it will be correct 
for your location!  Right click on the clock face and 
select Configure to reach the configuration panel.

An upgrade can be purchased that unlocks the features 
of a Universal Time Clock that can be displayed 
alongside the Sidereal Clock, Sidereal Time Alarms, 
and a Sideral Time Calculator.  

What is a sidereal clock?  Astronomy buffs (radio and 
the other kind) often use a special clock which is 
based upon "star time".  If you used your normal clock 
and timed when a distant star passed due south of you 
each night, you would find that each night it passed 
about 4 minutes earlier.  That happens because in addition 
to the 360 degrees the Earth rotates in 24 hours it also 
moves 1/365.25 of its orbit around the Sun. Thus, we swing 
into position to see a given point in the sky a little 
earlier every night. 

Celestial objects are located on the sky by a coordinate 
system which includes a celestial longitude (Right Ascension) 
and latitude (Declination).  The right ascension of a 
celestial object is same as the local mean sidereal time that 
the object will pass an imaginary line drawn from the 
celestial pole to due South ( 180 degrees azimuth). Thus, if 
you know the Local Mean Sidereal Time (LMST) you also know 
what objects are in meridian transit at your location.