(IAAC) OBJECT: M13 Hercules Cluster (Globular) INST: 18" F/4.2 Newt.

Observer:  Todd Gross
Your skill:  Intermediate 
Date and UT of observation: 2/7/99 10:00GMT
Location & latitude: 22 mi. West of Boston, Ma. 42.3N
Site classification: Suburban
Limiting magnitude (visual): 4.5(estimated) zenith 
Seeing (1 to 10 - worst-best): about 3
Moon up (phase?): Yes, Gibbous
Weather: Mostly Clear
Instrument: 18" Stabilite Newt f/4.2 1925mm fl
Magnifications: 214X, binoviewer
Filters used: none
Object: M13
Constellation: Hercules
Object data: Globular Cluster
Magnitude: 5.8
Personal 'Rating' (at this aperture and sky condition): A+

After developing a CCD photograph (http://www.weatherman.com/edf.htm)
of M13, I wanted to try again with the 18" scope to see how much of 
the detail I could ascertain visually. A more overall description of M13
can be found with my previous 16" scope in the NETASTROCATALOG. 

I am happy to report that quite a bit of the detail in the CCD photo 
is there at the eyepiece too. The magnificent cluster breaks to individuals
down to the center of the core with detail seen. The outer arms (strings
of stars) branching out from M13 are not symettrical. There are two 
particular strings that come out, and flatten out on the NE side that always
give me a frame of reference. Within the core is a noticeable sideways 
"Y" dark lane on that NE side. Being that each leg of the Y is about the same
length, it is nick-named the "propeller". Also easily discernible is the
"little propeller", or a small group of stars just below the core (assuming
NE is "up") The bright group of stars near the center of the cluster is
shaped as a small "X". The bottom right hand part of the X is dimmest. 

I also searched for more dark lanes visible in the ccd photo. One was found
on the right hand (north) side coming off the core, as a straight-line
gap following along a straight line of stars. Another thin dark lane in the 
vicinity of the "Y" was not discerned, probably because of poor seeing.


Boston Meteorologist Todd Gross

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