Antilhue - Chile

Messier 55 and Zelia
Home Clusters Galaxies Nebulae Solar System Bennett Catalogue Published images



Image Data

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