Designation |
M 55, NGC 6809, Bennett
122 |
Object type |
Globular cluster |
Coordinates |
19 h 40 min -
30° 58' Sagittarius (Sgr) |
Description |
Messier 55 is a quite large
globular cluster (about 19', roughly 2/3 of the Moon's apparent diameter)
with a loose appearence which makes it readily visually resolvable even in
small telescopes. M55 was originally discovered by Abbe Lacaille on
June 16, 1752, when he was observing in South Africa. Charles
Messier finally found and cataloged it on July 24, 1778, after having
looked in vain as early as 1764: this is a consequence of this object's
southern declination.
The multicolor bar to the lower right of the
cluster is a trace left by 10th mag minor planet (169) Zelia as it moved
at 35 arcseconds/hour from right to left (E -> W) throughout the 21 x 5 min
individual frames that make up this composite image.
Click here or on the image for a higher resolution
version. The field of view is 37 x 25 arcminutes with north
towards the bottom (180°).
|
Exposure |
NRGB 45:20:20:20 min @ -20°C
; all exposures unbinned, no filter on luminance |
Camera |
SBIG STL-11000 with Astronomik
Type 2 RGB filterset - selfguided |
Optics |
RCOS 14.5" Ritchey-Chrétien
@ f/9
(prime focus) |
Mount |
Astro-Physics AP1200GTO |
Software |
MaxIm DL/CCD, Sigma Pre
Beta 11, Adobe
Photoshop CS |
Location - Date - Time |
San Esteban (Chile) - 19Jul2006 @
06:00
UTC |
Conditions |
Transparency 7/10, Seeing 6/10, Temperature
+ 14°C |