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| Catalogue and alternative designations | NGC
6522, NGC 6528 and B298
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| Type | Globular clusters and dark nebula |
| Position | 18 04 21, -30 02 57 |
| Constellation | Sagittarius |
| Camera and Telescope | STXL16200 and 36.8cm RCOS Ritchey Chretien |
| Focal Ratio | F9 |
| Exposure Details | This is a simple LRGB image with Luminance = 150 minutes and Red = Green = Blue = 60 minutes. Luminance was unbinned and the colours were binned 2x2 |
| Description | NGC
6522 and NGC 6528 are two
globular clusters in a
dense star field in Sagittarius.
NGC 6522 is the larger at the
bottom. The dark nebula B
298 is visible at the top of the
frame to the left of NGC 6528
which is significantly reddened
by interstellar absorption. NGC
6522 has the apparent magnitude
of 10.5, apparent diameter of 2
arcminutes and is about 25,100
light years distant. It is
possibly the oldest cluster in
the milky way with an estimated
age of 12 billion light
years. NGC 6528 is
somewhat fainter at magnitude
10.65. It's 25,800 light years
distant.
Also of interest in this field is Baade's window which is an area of sky containing relatively little interstellar dust in the line of sight from our solar system. It is centered on NGC 6522. The astrophysical significance of Baade's window is that it provides a relatively unimpeded view of the galactic centre. This was first recognised by Walter Baade in 1942.
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