M3

M3 is one of the most outstanding globular clusters, containing an estimated half million stars.  At a distance of about 33,900 light years, it is further away than the center of our Galaxy, the Milky Way, but still shines at magnitude 6.2, as its absolute magnitude is about -8.93, corresponding to a luminosity of about 300,000 times that of our sun.  M3 is thus visible to the naked eye under very good conditions - and a superb object with the slightest optical aid. Its apparent diameter of 18.0 arc minutes corresponds to a linear extension of about 180 light years; Kenneth Glyn Jones mentions an estimate of even 20 arc minutes from deep photographic plates, corresponding to about 200 light years linear diameter.  It appears somewhat smaller in amateur instruments, perhaps about 10 minutes of arc.  But its tidal radius, beyond which member stars would be torn away by the tidal gravitational force of the Milky Way Galaxy, is even larger: About 38.19 minutes of arc. Thus, this cluster gravitationally dominates a spherical volume 760 light years in diameter.

Date Taken:
- 3/30/2007

Equipment Used:
- TMB 203 F/7
- SBIG STL-6303
- Paramount ME
- FLI PDF
- Astrodon 50mm filters

Exposures:
- Red:  20x3 minute subs, totaling 1 hour
- Green: 20x3 minute subs, totaling 1 hour
- Blue:  20x3 minute subs, totaling 1 hour

Processing:
CCDStack:
- Initial sub registration
- RGB combine
- Deconvolution (Positive Constraint, 20 runs)
- DDP

PSCS2:
- Gradient control (see my gradient control tip in the tips and tricks section)
- Noise control (NeatImage)
- Slight sharpening via Smart Sharpen in PS-CS2

Further details available at:
http://www.flemingastrophotography.com/m3dss.html