M13 - Hercules Globular Cluster

by Chuck May 10, 2013

Astronomy Observation Record


Date: 5-9-2013 Time: 9:30 p.m. Location: Brambly Hill
Instrument: Z10 Aperture: 254mm Focal length: 1250mm
Eyepiece/Magnification: 32/ 13/ 9/
Transparency: Seeing:


Object Notes

Cor Caroli

 Used this double to align finder scopes tonight. Something more interesting than a bright star.


M13 appears in the finder as a faint blur. It is centered in the finder just as nHerc reaches the edge.

At low power (32mm) M13 is a gray blur that resolves into a grainy patch with averted vision. The best focus for averted vision was HIP81848 up and to the right of M13 in the field of view. There is a rich field of background stars that set off the patch of M13 nicely.

Medium power (13mm) brings out individual stars around the edges of the cluster. The stars form gently curving arcs with gaps between. The center remains a glow, but now with surface irregularities suggesting structure within. Filed stars are now dimmer than the cluster and the cluster dominates the field of view.

With high power (9mm) the cluster fills the field of view. There is an amazing sense of depth with tendrils of stars reaching out toward me. The center, while still a mass of unresolved stars has a subtle texture that suggests additional layers lying within.


Backyard Astronomy

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