Messier M21


Object Information
Messier object: M21
NGC (New General Catalog) number: NGC 6531
Discription: Open Cluster
Located in constellation: Sagittarius
Right ascension in hours:minutes: 18:04.6
Declination in degrees:minutes: -22:30
Visual magnitude: 6.5
Size: 13.0 arc minutes
Image size: 55.23 arc minutes high by 40.98 arc minutes wide
Image orientation: North is top, East is left
Detailed discription of M21 in SEDS Messier database
Other Messier galleries, images or catalogs

Observing Log
Date September 20, 1998
Time at end of first CCD image 20:49 PDT
Time at end of last CCD image 20:53 PDT
Observing Location: At home on the drive way
Observation of object: M21 is a small irregularly open cluster with few stars.
Sky Conditions
Sky transparency: 5.2 (Magnitude of the faintest star visible with the unaided eye in Ursa Minor)
Notes: Image taken over Portland, Oregon, U.S.A. sky glow.
Moon sets at 19:28 PDT on September 20, 1998
Astronomical twilight ends in the evening at 20:51 PDT on September 20, 1998
Astronomical twilight starts in morning at 5:11 PDT on September 21, 1998
Observing Equipment
80 mm aperture refractor telescope and CCD Cookbook Camera
CCD image time: 4 -60 seconds images added together
CCD dark calibration frames: 4 - 60 seconds dark frames

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