Messier 7 - Ptolemy's Cluster

Observation Notes:

A beautiful, wide open cluster near the stinger of Scorpius. While the bulk of the cluster filled the 1.4° view, the more concentrated portion spanned about 15-20'. This concentration was bounded by a square of brighter stars. The SW corner of that square appeared to be marked by a reddish star, while a row of 6 stars spanned the E edge like a spine. As low as this was in the haze of the southern sky, it was still a striking view.

Factoids:

This cluster was recently named after Ptolemy who described it in 130 AD as a "nebula following the sting of Scorpius". M7 is an open cluster consisting of 80 stars brighter than 10th magnitude. It is 800 to 1000 light years distant, and spans 20-25 light years across. The age of the cluster is estimated at 220 million years. The whole group is approaching us at 14 km/sec. The brightest star is a yellow giant. (Thus demonstrating my current ignorance in estimating the color of stars through the eyepiece--it looked red to me, at least in comparison to the neighboring stars.)

SubjectM7/NGC 6475
ClassificationOpen Cluster
PositionScorpius [RA: 17:53.9 / Dec: -34:49]*
Size*80'
Brightness*3.3
Date/Time10/3/04 - 8:00 PM
Observing Loc.Flagstaff, AZ - Home
InstrumentOrion SVP 6LT Reflector (150 mm dia./1200 mm F/L)
Eyepieces/Mag.32 mm (37X)
Seeing5/10
TransparencyMag 4.5

* Based on published data.

The Cerulean Arc

My weblog for
everything else non-astronomy

Pin at will!


(Thanks for maintaining
return links.)

About this Entry

This page contains a single entry by Jeremy Perez published on October 3, 2004 8:00 PM.

Messier 69 was the previous entry in this blog.

Observing Report - 10.03.2004 is the next entry in this blog.

Find recent content on the main index or look in the archives to find all content.

Categories

Monthly Archives

Powered by Movable Type 5.2.3