Globular Cluster M10 (NGC 6254), class VII, in Ophiuchus ".

RA 16 : 57.1 (h:m); DEC -04 : 06 (deg:m); Distance 14.300 (light years);
Visual Brightness 6.6 (mag) ; Apparent Dimension 20.0 (arc min)

Messier 10 (M10, NGC 6254) is one of the bright globulars populating constellation Ophiuchus.
This 7th mag globular cluster appears at about 8 or 9 arc minutes diameter when observed visually in smaller instruments. Average photos show it at about 15.1 arc minutes diameter, and deep photos show it to reach out to about 20 arc minutes, or 2/3 of the diameter of the Full Moon. At its distance of 14,300 light years, this corresponds to a linear diameter of 83 light years.

Source and more: SEDS

M10 - Globular Cluster
July 12, 2009 21:10 - 21:44 UT.
Imaging: William Optics Zenithstar 80 ED II APO, f/6.8 [focal length 545 mm], Astronomik LRGB filters; ATK16IC camera.
Exposures: L: 13x90s [1x1]; RGB: 5x45s [2x2], unguided.