Open Cluster M50 (NGC 2323), type 'e', in Monoceros

RA 07 : 03.2 (h:m); DEC -08 : 20 (deg:m); Distance 3200 light years
Visual Brightness 5.9 (mag) ; Apparent Dimension 16.0 (arc min)

Open cluster M50 is probably about 3,200 light years distant. Its angular diameter of about 15x20' therefore corresponds to a linear extension of about 20 light-years, the central dense part being only about 10' or 10 light-years in diameter.
The visual appearance is described as a "heart-shaped figure" by Mallas and Kreimer.

Source and more: SEDS

February 10, 2008 20:19 - 20:56 UT.
Imaging: William Optics Zenithstar 80 ED II APO F/6.8 [focal length 545 mm], ATK16IC camera, Astronomik LRGB filters.
Exposures: L 18x90s [1x1]; RGB 5x30 [2x2]; all unguided.

March 10, 2007 19:50 - 20:01 UT.
Imaging: William Optics Zenithstar 80 ED II APO, f/6.8 [focal length 545 mm] with diagonal, Baader Infra Red Blocking Filter; SC3a b/w RAW camera.
24 unguided exposures of 20 seconds.

January 23, 2007 22:53 - 22:59 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 6 seconds.