M25
Open cluster in Sagittarius

10.1″ f/4.5, Mallincam DS432cTEC with 0.5 focal reducer and Astronomik UHC filter
Exposure = 5 sec, Live Stacked frames = 30, Gain = 41 of 250

Another bright open cluster in Sagittarius, M25 is approximately a 1/2 degree across and is listed as 13 light years across and 2000 light years distant. There are a few dozen bright stars amongst the hundreds of fainter ones in this cluster. A couple of curved arcs of stars exist near the center, forming longer lines pointing to brighter stars at the outer edges. The brightest star near the center is U Sagittarii, a cepheid variable whose magnitude varies between 6.5 and 7.2 over a period of 6.7 days; when this image was taken, it looks like U Sgr was close to the same brightness or a little dimmer than the bright star near the top edge of the frame, HIP 90900 which is magnitude 6.95, so this suggests U Sgr was near minimum, around 7.0 or 7.1.

M25 is the only Messier object that is listed in the the Index Catalogue, as IC 4725.

North at 1 o’clock, East at 10 o’clock