Some 7,000 light-years away, this pair of open or galactic star clusters is an easy binocular target and is visible to the unaided eye from dark sky areas. In fact, it was cataloged in 130 BC by Greek astronomer Hipparchus. Now known as h and chi Persei, or NGC 869 (left) and NGC 884, the clusters themselves are separated by only a few hundred light-years and contain stars much younger and hotter than the Sun. In addition to being physically close together, the clusters' ages based on their individual stars are similar - evidence that both clusters were likely a product of the same star-forming region.

This image was taken with a Canon 40D DSLR and Stellarview 102ED Refractor at f/5.6. 10 x 60 seconds @ ISO 1600 captured, aligned and stacked in Nebulosity. Final processing in Photoshop.

Globular cluster Messier 15 (M15, NGC 7078) is among the more conspicuous of these great stellar swarms. At a distance of about 33,600 light years, its diameter of 18.0 arc min corresponds to a linear extension of about 175 light-years, and its total visual brightness of 6.2 magnitudes corresponds to an absolute magnitude of -9.17, or roughly 360,000 times that of our sun. Its brightest stars are about of apparent magnitude 12.6 or absolute magnitude -2.8 or a luminosity of 1,000 times that of our Sun, and its horizontal branch giants are about of magnitude 15.6. Its overall spectral type has been determined as F3 or F4. The globular cluster is approaching us at 107 km/sec.

In amateur instruments, M15 appears somewhat smaller, perhaps about 7 arc minutes visually and 12.3 arc minutes photographically. On the other hand, the tidal radius of this globular cluster, beyond which member stars would escape because of the Milky Way galaxy's tidal forces is a bit larger: 21.5 arc minutes, corresponding to a distance of 210 light years from the cluster's center.

This image was taken with a Canon 40D DSLR and Stellarview 102ED Refractor at f/5.6.....20 x 30 second images at ISO 1600 captured, aligned and stacked in Nebulosity. Final processing in Photoshop.

The globular star cluster known as M92 contains several hundred thousand stars. It is located 26.000 light years from our solar system.

This star cluster is located within the constellation of Hurcules. It is visible in small telescopes. In 1781 the French comet hunter, Charles Messier, made it the ninety second, M92, of his now famous catolalog. However, lying only 9.5 degrees northeast of the spectacular globular cluster M13, it is often overlooked if not completely forgotten.

This image was taken with a Canon 40D and Stellarview 102ED refractor at F / 5.6. The exposure time is 20 minutes, 10 x 120 second @ ISO 1600.  Images calibrated in Nebulosity. Processing in Images Plus and Photoshop.

M13 is probably the most looked at and most beautiful object that can be seen in the Northern skies. Even modest amateur telescopes show it as a blazing ball of stars. Again we can be glad that instruments have improved since the days of Messier. When he cataloged this object as M13 in 1764, he described it as a "nebula containing no stars". This is about what one sees in a pair of binoculars today.

This color image not only shows that it contains so many stars that it just becomes a blob of light in the core with long exposure but further that the stars come in several different colors.

It is difficult to determine the exact number of stars, especially in the central core where they are most numerous, but 30,000 stars have actually been counted and estimates are that the cluster contains something like one million stars.

The total luminosity of M13 is over 300,000 times that of the Sun and the total mass is equal to perhaps half a million Suns. The brightest members of the cluster are red giants, each as bright as 2000 Suns. It is interesting to note that looking back from M13 ( a distance of about 21.000 light years ), the Sun could not be seen visually in even the largest telescope.

This image was taken with a Canon 40D DSLR and Stellarscopes 102ED Refractor @ f /5.6. 10 x 120 second images @ ISO 400 in Nebulosity.