NGC 6638 -- Globular Cluster in Sagittarus
“… A Miniature of M53”
The above quote is that of William Herschel who observed, NGC 6638, in 1814. This
dense small Globular Cluster was my surprise for the night. I believe that if it were not
stuck between the two large Globular Clusters M22 and M28 that it would be more
observed and appreciated than it is.
NGC 6638 is also easy to find since it is only ¾ of a degree from the bright star Lambda
Sagittarii and the cluster’s bright core is easily seen in the same low-power eyepiece as
the star. In the drawing, Lambda Sagittarii is the bright star at the edge of the drawing
at 9:00 o’clock.
Although the brightest stars in the cluster shine at magnitude 14 and thus below the
resolution of my 110mm refractor, I could still see that this globular had a complicated
internal structure. Its core seemed knotted with subtle extended arms of unresolved stars
radiating from its center. I found this globular mesmerizing for it seemed to not let me
visually solidify its core, but instead seemed to dance gracefully to a celestial rhythm that
I could not hear.