Bob Moler's Ephemeris Blog

Ephemeris for Tuesday, April 3rd.  The sun will rise at 7:18.  It’ll be up for 12 hours and 54 minutes, setting at 8:13.   The moon, 3 days before full, will set at 5:43 tomorrow morning.

The brilliant planet Venus is passing by the Pleiades star cluster.  It will be a great sight in the west in the evening.  Binoculars will help in picking out the Pleiads, as the individual stars of the Pleiades are called.  The celestial sphere is the ultimate reference frame for objects in the heavens.  It used to be the stars, but the stars move, the sun moves and the earth moves.  Now the standard for an unmoving frame of reference is distance quasars, the nearly stellar in size active cores of distant galaxies.  While they’re moving too, they are so far away we cannot detect any motion on the celestial sphere. Our earth centered frame of reference rotates within that at once in 26 thousand years as the earth’s axis precesses  due to the gravitational pull of the moon.

* Times are for the Traverse City/Interlochen area of Michigan.  They may be different for your location.

Addendum

Venus passing the Pleiades April 2 - 4, 2012. Created using Cartes du Ciel.

Click here for a Space.com write up on how  quasars are being used as  a reference for the GPS system.