Archive for November, 2007

Google Sky Constellation Boundaries

November 30th, 2007 1 comment

Southern Constellations in Google Earth SkyIn a recent post, OgleEarth mentioned the lack of constellation divisions in Google Sky’s default layers.  As Stefan says, these are pretty useful landmarks for finding your way around the night sky.  I’m guessing GSky might include something like this eventually, but until it does, here’s a simple add-on KML file which does the job.

Google Sky Constellations (130kB)

To keep things simple the file just includes boundary lines.  However , on screen constellation labels are available through Google Earth’s Layers in the side panel. So I suggest switching those on once the file is open. 

The coordinates for the KML were drawn from Davenhall & Leggett’s “Catalogue of Constellation Boundary Data”, from the file for equinox and equator 2000.  I made a couple of minor modifications to remove spurious lines near the celestial poles.   

One more thing:  If you turn on  Google Sky’s grid (View menu -> Grid) you’ll notice the borders are slightly skewed compared with the vertical and horizontal red lines of the grid.  Nothing to do with my cack-handed coding skills, honestly 🙂 .  It’s because the source data accurately takes into account the slight change in orientation of the earth’s axis of rotation (precession of the equinoxes) since the modern divisions were set in stone in 1930.