Deep Sky Object in Summer
M54, M69, M70 (Globular Clusters in Sagittarius)

Date & Time: M54: Jun 2 2001, 25:02 JST(+0900), 60sec. exposed 5shots
M69: Jun 2 2001, 24:18 JST(+0900), 60sec. exposed 6shots
M70: Jun 2 2001, 24:42 JST(+0900), 60sec. exposed 5shots
Optical: Meade 25cm(10") Schmidt-Cassegrain, afocal method with LV12mm eyepiece
Synthesized focal length f=2583mm (equivalent f=15222mm in 35mm film format)
Auto-guided with Meade LX200 Equatorial
Digital Camera: CASIO QV2800UX
Location: Ooizumi vil., Yamanashi pref.

Camera Settings: Mode.....1600×1200 FINE
Lens.....f=12.4mm (equivalent f=83mm in 35mm film format), Stop: F3.2
CCD sensitivity.....ISO160, White Balance.....Daylight

I'd like to show you three tiny globular clusters distributed around south of the asterism of "Teapot" of Sagittarius in this page. Many globular clusters are distributed surrounding the "Bulge" region of the central Galaxy seems like a convex lens. So the constellation of Sagittarius contains uncountable globular clusters because the center of Galaxy is positioned in the constellation. The Sagittarius occupies only 2% of all area of the celestial sphere, but surprisingly the constellation has about one third of all discovered globular clusters.
These three globulars have diameters of less than 3 arc minutes, you can see only nebula like dimmed images even if you use fairly large telescopes. Perhaps you will realize that M54 is a bit denser than other two.

M54 (NGC6715) / Globular Cluster, type III
R.A.18h 55m 5.9s (2000.0)
Dec.-30° 29' 00" (2000.0)
Apparent Size2.1'
Real Size55 light yrs.
Distance49,000 light yrs.
M69 (NGC6637) / Globular Cluster, type V
R.A.18h 31m 24.0s (2000.0)
Dec.-32° 21' 00" (2000.0)
Apparent Size2.3'
Real Size68 light yrs.
Distance23,000 light yrs.
M70 (NGC6681) / Globular Cluster, type V
R.A.18h 43m 11.9s (2000.0)
Dec.-32° 17' 59" (2000.0)
Apparent Size2.5'
Real Size59 light yrs.
Distance65,000 light yrs.



Copyright(c) 2001 by Naoyuki Kurita, All rights reserved.
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