Deep Sky Object in Summer
M25 (Open Cluster in Sagittarius)

Date & Time: Aug 7 2010, from 22:45 to 23:04 JST(+0900)
Composed 3 shots with 8 minutes exposed
Optical: TAKAHASHI 16cm(6.3") epsilon (f=530mm, F3.3)
with IDAS LPS-P1 Light-pollution suppression filter
Auto-guided with TAKAHASHI EM-200 Equatorial & Meade Pictor 201XT
Digital Camera: Nikon D50 (Remodeled)
Location: Koumi town., Nagano pref.

Camera Settings: Recording Format...12bit CCD-RAW, converted to 16bit TIFF(3008×2000)
CCD Sensitivity...ISO800

M25 (IC4725) / Open Cluster, type d, I 3 m
R.A.18h 31m 36.0s (2000.0)
Dec.-19° 15' 00" (2000.0)
Apparent Size40'
Real Size21 light yrs.
# of Stars30
Distance1790 light yrs.
You can find a medium-sized open cluster of M25 (no NGC number, IC4725) being buried under the Milky Way around the northern region of Sagittarius. Gamma Sgr is a good mark to catch the cluster about 6 degrees north from the star. The cluster has a diameter of 40 arc minutes and contains 30 fine stars.
And you can enjoy many other attractive celestial objects around this field like the Star Cloud in Sagittarius, the Omega Nebula (M17) and so on. Perhaps you'll notice that M25 has a dark lane dividing the cluster into north and south regions; it's one of characteristics of the cluster. M25 is estimated about 1800 light years away.



Copyright(c) 2010 by Naoyuki Kurita, All rights reserved.
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