This a method of determining how many constellations you can observe for observers in the Northern hemisphere. First, the North latitude of your location determines how far South declination can be seen with a flat South Horizon. Portland, Oregon is at 46 dregrees North latitude which means observers in Portland can see stars to -44 degrees declination. The equation for North latitude locations is Declination = (your_latitude-90).

The more sky can seen when observing closer to the equator. For example, in Singapore which is 2 degrees North latitude an observer can see from +90 to -88 degrees declination which is almost the complete sky.

Next, using a star atlas like "The Bright Star Atlas 2000.0" (by Wil Tirion) determine what constellations and stars are between 90 degrees declination, the celestial North pole, and your farest South declination. This is the part of the sky you can observe.

Side note: only the bright stars are seen close to the horizon because the nearer a star is to the horizon the fainter the star appears because of atmospheric absorption.

© 1998-2003 David Haworth