imaged these clusters with iTelescope
T21 on the night of April 26th with a waning gibbous moon in
the sky. Image
two globular clusters are separated by less than a degree in the
sky. They provide a wonderful
study in contrasts, for it is difficult to imagine two more
different clusters. M53
(right) is your classic globular with a bright rich center. NGC
5053 (left) is a most unusual
globular cluster, it's stars are spread much more loosely and
irregularly, appearing more like an open cluster than as the
familiar tightly wound globular.
M53 was discovered by Johann Bode in 1775.
Smyth reportedly called M53 an "interesting ball of
innumerable worlds." Visible in binoculars, small telescopes,
and even finders as a small ball of haze, it is only in 6-inch or
larger scopes that it begins to grudgingly give up a few of its
myriad stars. As you move to larger apertures and higher
magnification, more and more stars become resolved. Sir William
Herschel said of M53 that is was "one of the most beautiful
sights I remember to have seen in the heavens." In larger
scopes at magnifications of 250x or greater, this cluster is quite
beautiful. It is somewhat asymmetrical for a globular, with a
tight core that is resolved when the seeing is good.
M53 is clearly visible in my 8x52
finder scope, appearing as a big fuzzy star. In my 18-inch at 94x
it appeared as a round haze with bright center overlaid with a
smattering of resolved stars. At 270x the view was very different.
It now filled 1/2 of the field of view and my eye was met by a
myriad of countless stars. My notes began with a single word,
"Spectacular!" The brighter inner region now
resolved into many stars, very regular in appearance and
distribution. But across the face of the cluster lies another
population of brighter stars. These stars are scattered very
irregularly and extend far away from the cluster center. It must
be these stars that are first resolved at low magnification or in
smaller apertures. Perhaps this dichotomy is what Smyth was
talking about when he described M53 as "a mass of minute
stars 11-15 mag. and from thence to gleams of star-dust, with
stragglers." Increasing the magnification still more, M53
appeared absolutely wondrous in my 4.8mm Nagler (425x), filling
the field with myriad, tiny points of light.
Of NGC 5053 Walter Scott Houston
wrote , "In large instruments it is a little gem of woven
fairy fire." It was discovered by William Herschel in March
of 1784. As globular clusters go, NGC 5053 is pretty faint. It
didn't jump out at me like most do. In my 18-inch at 94x it
appeared primarily as a faint, mostly round, smattering of stars
embedded in a large very faint glow. The entire cluster appears
diffuse--there is no bright core of tightly bound stars as seen in
most examples of its type. At 270x NGC 5053 resolved into an
irregular smattering of faint stars. At that magnification it
appeared much more like an open cluster than a globular.
Oddly, the fainter NGC 5053 is
actually the closer of the two (although not by much). Both are
located far above the plane of the Milky Way. In fact, NGC 5053 is
one of the intrinsically faintest of the known globular clusters,
shining perhaps with the light of a mere 16,000 suns. It is also
one of the most metal-poor, indicating that it formed from
interstellar gas that had not been significantly enhanced with the
byproducts of many generations of stars.
that we have made the window as small as possible to fit the space
SkyTools 3 Nightly Planner is set up (above) for May 2 at Tierra
Del Sol for
a 10-inch (25 cm) telescope. This location has a naked-eye limiting magnitude of
6.9. The red-dashed line in the graphic at the top displays
the altitude of M53 during the night. The shading is the actual brightness of the
sky taking into account moonlight, twilight, and light pollution.
at the line we can see that the best time to observe M53 (and NGC
5053) will be after 11 PM. SkyTools has calculated that you
can go ahead and start looking at 20:45 (the Begin column in the
planner). The best view will be at 23:12, and the good views will
last until 03:21, when it is low enough in the sky that we are now
looking through too much air. These
calculations are unique to SkyTools, which samples the visual
contrast of the object as seen in the eyepiece over the course of
is easy to find less than a degree to the northwest of Alpha Com.
Greg Crinklaw — Developer of
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