## 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.

Star Magnitude Table

Magnitude Range Number of Stars
per Range
Cumulative
Stars
% Increase in
Stars Seen
-1 -1.50 to -0.51 2 2
0 -0.50 to +0.49 6 8 400%
1 +0.50 to +1.49 14 22 275%
2 +1.50 to +2.49 71 93 423%
3 +2.50 to +3.49 190 283 304%
4 +3.50 to +4.49 610 893 316%
5 +4.50 to +5.49 1,929 2,822 316%
6 +5.50 to +6.49 5,946 8,768 311%
7 +6.50 to +7.49 17,765 26,533 303%
8 +7.50 to +8.49 51,094 77,627 293%
9 +8.50 to +9.49 140,062 217,689 280%
10 +9.50 to +10.49 409,194 626,883 288%
11 +10.50 to +11.49 1,196,690 1,823,573 291%
12 +11.50 to +12.49 3,481,113 5,304,685 291%
13 +12.50 to +13.49 10,126,390 15,431,076 291%
14 +13.50 to +14.49 29,457,184 44,888,260 291%
15 +14.50 to +15.49 85,689,537 130,577,797 291%
16 +15.50 to +16.49 249,266,759 379,844,556 291%
17 +16.50 to +17.49 725,105,060 1,104,949,615 291%
18 +17.50 to +18.49 2,109,295,881 3,214,245,496 291%
19 +18.50 to +19.49 6,135,840,666 9,350,086,162 291%
20 +19.50 to +20.49 17,848,866,544 27,198,952,706 291%

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.

Telescope Limiting Magnitude

Aperture
Inches
Aperture
mm
Faintest
Magnitude
2 51 10.3
3 76 11.2
4 102 11.8
6 152 12.7
8 203 13.3
10 254 13.8
12.5 318 14.3
14 356 14.5
16 406 14.8
18 457 15.1
20 508 15.3
24 610 15.7
30 762 16.2

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

Aperture and Limiting Magnitude Table

Aperture
Inches
Aperture
mm
Theroetical
Minimum Magnitude
Faintest Magnitude
Easly Observed
1.97 50 10 6
3.94 100 12 8
7.87 200 14 10
15.75 400 16 13