Open Cluster M18 (NGC 6613), type 'd', in Sagittarius
RA 18 : 19.9 (h:m); DEC -17 : 08 (deg:m); Distance 4900 (light years);
Visual Brightness 7.5 (mag); Apparent Dimension 9.0 (arc min)
M18 is best observed in small telescopes, which show over a dozen of fairly bright stars; based on a distance of 4900 light years, its linear diameter should be about 17 light years.
Source and more: SEDS
Wide field image of M16, M17 and M18
August 4, 2009 20:52 - 21:30 UT.
Imaging: 50mm SLR Photolens, Astronomik Ha filter; ATK16IC camera.
Exposures: Ha: 4x300s [1x1] unguided; RGB: not captured: these objects are very low in my skies and my imaging window is only 25 minutes ...
August 23, 2008 20:06 - 20:12 UT
Imaging: William Optics Zenithstar 80 ED II APO, f/6.8 [focal length 545 mm], Astronomik Lum filter; ATK16IC b/w camera, K3CCDTools.
Exposures: Lum 5x90s, unguided. RGB could not be captured: this object is almost impossibly low for me with trees blocking my view.
July 14, 2006 22:31 - 22:35 UT
Imaged with LX200 10-inch f/10 telescope with 0.33 Focal Reducer operating at f/4.06 [focal length 1015mm],
Vesta Pro-SC3a b/w RAW camera, Baader Infra Red Blocking Filter.
30 unguided exposures of 5 seconds.
As I live at 52 degrees North, M17 (with DEC -16) is very low for me, as you can see on this picture.
And M18 [DEC -17] is even lower ...