Designations: M3, NGC 5272 Visual Magnitude: 6.3
Visual Description: 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
Exposure: 180 and 300 second
exposures
Other: SBIG
STV autoguider
Image Processing: 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.
The Visual description of the M3 Globultar Cluster was writen by Steven James O'Meara in the book "The Messier Objects" by Stephen James O'Meara. Page. 45. ISBN number 0-521-55332-6.
Copyright(c) 2007 Doug Sanqunetti. All rights reserved
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