Clobular Clusters

This is an image of M13, the Globular Cluster in the constellation Hercules. It was done by a median combine of 10 unbinned - 3 second, unguided exposures at -15 degrees with the ST-10XME, CFW-10 Astrodon clear IR-block filter through the BRC-250 on a MI-250 mount with the Gemini Level 4 computer. Focus was done with the FLI DF2 focuser. Imaging was controlled with Maxin DL. The images were aligned using Mira Professional and combined in CCD Stack with a median combine. Additional image processing was done in PhotoShop CS2. It is interesting to note that "the Propeller" is visible in the lower right portion of the cluster.

This is an image of M15, the great globular cluster of the constellation, Pegasus. It was made of 6 unbinned 5-minute guided subexposures with the same set up as M13 above.

M13 (NGC6205) “The Great Globular Cluster in Hercules”, NGC 6207, and IC 4617

Constellation: Hercules
RA: 16h 41.7m
Dec: +36 Degrees 28 Minutes
Distance: 25,100 Ly
Magnitude: 5.8
Size: 20 arc minutes (145 light years)
Dates: 05 August 2007 to 14 August 2007
Location: The Dark Horse Observatory
Kimberton, PA

Luminance: 20 5-minute frames
Red: 18 5-minute frames
Green: 18 5-minute frames
Blue: 19 5-minute frames
Total: 390 minutes (6 1/4 hours)

Equipment:
Telescope: BRC-250
CCD: SBIG ST-10XME
Filterwheel: SBIG CFW-10
Filters: Astrodon Series E
Focuser: Finger Lakes Instrumentation DF2
Rotator: Optec Pyxis 2 inch Rotator
Mount: Mountain Instruments MI-250 with Gemini Level 4
Pier: Pier-Tech 3 Pier

Software:

Image Acquisition:
CDDAutopilot 3
Maxim DL
FocusMax
The Sky 6
Image Processing:
CCDStack
Mira Pro
Adobe PhotoShop CS3
Russell Croman’s Gradient Xterminator
Noel Carboni’s PhotoShop Tools
Kodak GEM noise reduction Plug-in

M13, the great globular cluster in Hercules shines at a magnitude of 5.8 with an apparent size of 20 arc minutes corresponding to a diameter of 145 light years. It is located at a distance of approximately 25,100 light years. This globular cluster is estimated to contain several 100,000 stars. It was first discovered by the English astronomer Edmond Halley and was cataloged by Charles Messier on June 1, 1764.

One interesting feature of M13 are the presence of several star-poor regions three of which form the shape of a three-bladed propeller, hence its appellation, “the propeller.” This is visible in the central region of this image. Additionally, M13 contains one young blue star, Barnard No. 29. Since globular clusters are relatively old it is postulated that this was a captured field star.

Also visible in this image at the left edge is the galaxy, NGC 6207 which was the site of a recent type II supernova, SN2004A. NGC 6207 is only magnitude 12.2 and spans only 3.3’ x 1.7’. It is estimated to be at a distance of 22 million light years, therefore its appearance in the image reflects a background object. An even smaller and fainter galaxy, IC 4617, located between the other two objects is also captured in this image. IC4617 has a brightness of magnitude 15.5 and is only 1.2’ x o.4’in apparent size.