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STARS

How Many Stars You Can Observe

The following table shows the number of stars in each magnitude range, the cumulative number of stars from -1 magnitude to the current magnitude of the row, and the precentage increase in stars with an increase of one magnitude.

On the average when you can increase the faintest stars you can observer by one magnitude fainter you can observer about three times (3X) more stars. For example, if can observer magnitude 2 stars in the city and can observer magnitude 3 at your home you should be able to see three time more stars at your home. If you go to a star party where you can see magnitude 5 stars you should see about 27 times more stars at the star party as compared to observing in the city (magnitude 2 to 3 is about 3x, magnitude 3 to 4 is about 3x, and magnitude 4 to 5 is about 3x for total of 3x3x3=27).

The number of stars in the table are for the complete sky. Under ideal conditions an observer can only see one half of the sky at any time. Also the stars are not evenly distriubuted across the sky. Some parts of the sky have more stars per unit sky area than others parts of the sky.

Data is based on the Tycho Catalogue which was obtained from page VII of the Millennium Star Atlas, Volume I, Sky Publishing Corporation and European Space Agency. The Tycho Catalog is believed to be 99.9 percent complete to magnitude 10.0 and 90 percent complete to magnitude 10.5. Table data for magnitudes 11 to 20 are projected on the average increased of 291%. 291 % is the average increase of stars between magnitudes 6 to 7, 7 to 8, 8 to 9, and 9 to 10.

The dimmest star that can be seen without optical aid in a dark sky is around 6 magnitude depending upon the observer's eyesight and sky conditions. The below Telescope Limiting Magnitude table gives a rough idea of the faintest star magnitude that can been seen through a different aperture telescopes. The magnitude values are not precise because many factors affect the magnitude values such as optics, sky conditions, etc. Also the 2 inch row can be use for a 10 x 50 binoculars which is very close to a 2 inch (51 mm) telescope.

Telescope Limiting Magnitude Table is from page 5 in the excellent book Star Ware, Second Edition by Philip S. Harrington, John Wiley & Sons, Inc.

Aperture and Limiting Magnitude Table from The Guide to Amteur Astronomy by Jack Newton and Philip Teece, Second edition, page 33.

© 1998-2003 David Haworth