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NGC
7006 is one of two prominent globular clusters in Delphinus.
It is small and compact and may be mistaken for a faint star in
small instruments at low magnification. One of the many
distinguishing characteristics of this globular is that it lies much
farther away than most; nearly 4 times farther away than M15, and
ten times farther away than Omega Centuari.
In my 18-inch f/4.5 Dob
it appeared faint, small, diffuse, and not at all resolved at 94x.
I was struck by how comet-like it appeared at first glance, looking
more like a telescopic comet than most other globulars.
Walter Scott Houston
claimed that, "Large telescopes may show it with a clumpy
appearance, but I doubt it can be resolved in any amateur
instruments." It's not clear to me when he wrote these
words. Perhaps they were written before large aperture amateur
instruments became generally available. In my 18-inch f/4.5
Dob at 430x I was able to resolve the majority of the brighter stars
to within about 10% of the cluster center. Most strikingly,
this globular displayed a hazy outer envelope of faint, unresolved
stars, surrounding the partially resolved central region. This
makes an interesting contrast with the other globular in Delphinus
(NGC 6934) which can appear in the opposite sense; with a halo of
resolved stars surrounding an unresolved central region.
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