M3 - Globular Cluster

Designations:	M3, NGC 5272
Object Type:	Globular Cluster
Constellation:	Canes Venatici
RA:	13 hrs 42.2 min	Dec:	+28 deg 22 min
Magnitude:	6.3	Size:	19 arcminutes
Distance:	32,000 light years
Discoverer:	Messier, 1764

M3 is another challenging object for beginners. Not only is it a great naked-eye challenge, but the stars in the cluster itself can be used to test telescopic vision. Although it is located in Canes Venatici, it's best to use the stars of Bootes and Coma Berenices as guides. M3 is just northeast of an orange 6th- magnitude star about two finger-widths due east of Beta Comae Berenices and 10 degrees (one fist) north and slightly west of Eta Bootis. Once located in binoculars, this cluster is easier to see with the naked eye than M2 for several reasons: it is a half- magnitude brighter, there is a 6th- magnitude guide star next to it, and it resides much higher in the northern hemisphere sky. Here's the catch: M3 lies so close to the guide star it may be hard to resolve the two! The observed color of globulars is open for debate. Some astronomers argue that the colors are merely optical illusions. But I find that at very low magnifications most bright globulars show distinct albeit faint colors - mostly shades of yellow and blue. Other observers have independently seen these tints, and true-color images of globulars reveal them as well. Visual observers should look for the mysterious dark spots that inhabit M3's nuclear region. Lord Rosse first noted them from his observatory at Birr Castle in Ireland as "small, dark holes"; they show up well on high-resolution photographs.

Telescope:	TMB 115 f7 Apochromatic Refractor
Focal Length:	805 mm
Mount:	Takahashi NJP 160
Camera	Starlight XPress MX916
Guider:	SBIG STV autoguider
Exposures:	4 180-second images and 5 300-second images were combined for this image. The shorter exposure image provided more detail in the core of the cluster without the usual core burn out. The 300-second images were used to provide more detail outside of the core. The images were combined using Adobe Photoshop. A small amount of sharpening (unsharp mask) was used to sharpen all images.
Location:	Cicero, IN
Software: