M103 (NGC 581)

All Images Copyright Steve Cannistra

Please click here for a larger image.

Magnitude:  7.4
Size: about 6'
Distance: 8,500 light years
RA: 1h 33m 22s
Dec: 60 degrees 39' 29"

This beautiful open cluster is an under-appreciated target in the constellation Cassiopeia, which contains many other clusters such as M52 and NGC 663.  Although it is called M103, it was not discovered by Messier but rather by Pierre Mechain in 1781.  This little jewel can easily get lost in the background of Milky Way stars, and it can be difficult to appreciate during visual observation.  Nonetheless, this cluster makes a wonderful target for astrophotography, especially with the nice contrast provided by several red giants in the field.  At 8,500 light years distant and with dimensions of 6 arcminutes, its 172 members span about 15 light years across.  Here is another image of M103 taken by Rob Gendler.  More information about this open cluster may be found here.

Photographic Details:

Date:  November 25, 2005
Scope:  Takahashi FS-102 at f6 with TOA-130 focal reducer, on the G11 Losmandy Mount.
Autoguider:  SBIG STV with e-finder.
Camera:  SXV-H9.

Astronomiks Type II  RGB filter set; IDAS-LPS filter.
Exposures:  Luminance filter, 6 x 4'; R, G, B 5 x 4' (all unbinned).  Total exposure: 84 minutes.
Conditions:  Temperature 22 degrees F; average transparency, average seeing; calm; clear. 
Post-processing:  No darks were needed for this image.  Subs were bias subtracted, aligned, and combined in Maxim.  DDP performed in ImagesPlus (IP), with further processing in Photoshop CS (16 bit format).  Diffractions spikes created with two pieces of kite string placed perpendicularly in front of the telescope.
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