The Caldwell Objects

with a sheen of light, especially at low magni-
fications. The key, then, must be power. W need e
to push the magnifications of our telescopes to
the limits in order to penetrate this inner sanctum.
How much power is needed? From
Houston, Texas, Barbara Wilson viewed NGC
7662 at 356x through a 13.1-inch f/4.5 reflector yet
failed to see the star. Roger Clark suggests an
astoundingly high power of 720x for telescopes 2
to 8 inches in diameter. "This object provides a
good example of how the upper limit to useful
magnification depends on image brightness,"
Clark says of NGC 7662. "The lesson is that if you
are observing an object and feel that higher
magnification may bring out more detail, go
ahead and ignore the 'accepted' magnification
limit of 60x per inch of objective diameter."
Without question, the central star is there in
photographs and CCD images of the Light Blue
Snowball. Furthermore, while Hartung could not
directly see the star with his 12-inch reflector, he
did perceive its presence as a continuous streak
when he inserted a prism into
The Caldwell Objects
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the telescope's light path, spreading the star's
light (and the nebula's) into a spectrum. Whoever
does see the star will be rewarded by a rare sight:
that of a hot, blue dwarf that has driven its own
atmosphere away. As seen today from Earth, the
nebula's shells are expanding outward at rates
measured in tens of km per second; the bright
inner shell already spans three-tenths of a lightyear
and its faint outer envelope extends some 2
light-years. Had its precursor been our Sun, the
outer envelope of NGC 7662 would stretch
halfway to the nearest neighboring star.
Before you leave this fabulous object, I'd like
you to search for an asterism I chanced upon
while seeking NGC 7662. It is a nearly exact
replica of M73, a Y-shaped grouping of four l0thmagnitude
stars in Aquarius. The four close-knit
stars in the Andromeda Y appear in the
Millennium Star Atlas. The 3'-long group lies 2°
south-southwest of 13 Andromedae and just 30'
east of the 11th-mag-nitude galaxy NGC 7640.
The Y is oriented northeast to southwest.
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