M3 is estimated to contain approximately 500,000 stars and to be at a distance of 33,900 light-years from Earth, The cluster spans an angular distance of 18 - 20 arcminutes corresponding to a diameter of 180 - 200 light-years.

Additional information about the cluster can be found at the following links:

http://antwrp.gsfc.nasa.gov/apod/ap980719.html

http://www.seds.org/messier/m/m003.html

Iris is an outstanding piece of software which is written and maintained by Christian Buil and kindly offered at no charge (although it is copyrighted).

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Detailed mapping information for this image using the SIMBAD astronomical database can be found here or by clicking on the image to the left. The database was used to generate a map of this portion of the sky and the image was superimposed upon the SIMBAD map. This allowed proper orientation and scaling of the map along with identification of objects captured in the image.

Information on the SIMBAD database can be found at the link below:

SIMBAD MIRROR SITE

The SIMBAD system database provides basic data, cross-identifications and bibliography for astronomical objects outside the solar system.