Antilhue - Chile
Antilhue - Chile
|
|
|
| Designation | Messier 4 ( M 4 ), NGC 6121, Bennett 75 |
| Object type | Globular cluster |
| Coordinates | 16h 24 min - 26° 32' Scorpius (Sco) |
| Description | M 4, size 26', is a loose
globular, classified by Dreyer as an open cluster. He also
described a bar of 8-10 stars across the center of
the cluster and called it extremely rich (for an open cluster).
Bennett observed it with a 5-inch short-focus refractor, including
it in his list of cometary objects as number 75. His coded annotation
describes it as a circular or slightly elliptical extended object, fully
or partially resolved into stars under a higher magnification, with a
larger aperture or in very good conditions.
This marginal naked eye object ( mag 5.9 ) is located 1.3° west of Antares. At less than 6.500 light years, Messier 4 may well be the nearest globular cluster to the sun. Interstellar absorption in this direction is estimated at 1.4 magnitudes and accounts for the yellow-orange colour. Click on the image for higher resolution (1600 x 1050). The field of view is 37 x 25 arcminutes with north towards the top. |
| Exposure | LRGB 50:15:15:15 min @ -20°C ; all exposures unbinned |
| Camera | SBIG STL-11000 with Astronomik Type 2 filterset - selfguided |
| Optics | RCOS 14.5" Ritchey-Chrétien @ f/9 (prime focus) |
| Mount | Astro-Physics AP1200GTO |
| Software | MaxIm DL/CCD, Sigma Pre Beta, Registar, PixInsight V.1, Adobe Photoshop CS |
| Location - Date - Time | San Esteban (Chile) - 11Apr2005 @ 08:00 UTC |
| Conditions | Transparency 8, Seeing 8, Temperature + 7°C |
