The Caldwell Objects

ightest stars shine
around 4th magnitude
and form a nearly
flattened diamond. Its
central and easternmost
stars also can be seen as
a dipper — a comforting
sight for us northern
ers, who have grown fond of dippers in the polar
regions of the sky. Two of the dipper's bowl stars,
Gamma (γ) and Delta 1,2 (δ 1,2 ) Chamaeleontis,
even point to a spot within 2° of the South
Celestial Pole. The dipper also harbors our target,
NGC 3195 (Caldwell 109), which lies halfway
between 5th-magnitude Zeta (ζ) Chamaeleontis,
the closest star in the dipper's handle to the bowl,
and the slightly brighter pair of stars that
constitute Delta 1,2 Chamaeleontis, the bowl's
southernmost "star."
Small-telescope users may have some difficulty
picking out the magnitude -11.6 glow of
NGC 3195 from the background sky at low
power. Indeed, it is the second-faintest planetary
in the Caldwell Catalog. And though NGC 40
(Caldwell 2) in Cepheus is nearly a full magnitude
fainter, it is easier to see because it has a
magnitude-11.6 central star. NGC 3195 does not
share this visual luxury; its central star shines at a
feeble magnitude 15.3. Fortunately NGC 3195 has
a high surface brightness (10.6 magnitudes per
square arcminute). So all a
The Caldwell Objects
109
small-telescope user needs to do is sweep the
region between Zeta and Delta Chamaeleontis
with powers between 75x and 100x and look for a
swollen star. As with many planetaries,
magnification is needed to differentiate the object
from field stars. Averted vision helps, too, since
it captures the nebula's outer shell and causes the
planetary to swell. Kent Wallace of western
Australia writes that through an 8-inch Schmidt-
Cassegrain telescope at 62.5x the planetary
displays a "nice small disk" under averted vision.
He uses an Oxygen III (O III) filter, however, to
find the nebula. Wallace concurs that the
planetary is easier to see at 100x and up.
Large-instrument users will have no problem
sighting the nebula, but seeing detail in it
will still be a challenge. Australian amateur
Andrew Murrell observed NGC 3195 in February
1999 with a 20-inch f/5 Dobsonian. He saw it as a
slightly flattened ring and noted a brightening on
the ring's inner eastern edge. The planetary
responded well to an Ο III filter, which made it
appear slightly larger and its annular shape
easier to pick out. But Murrell saw little else. In
August 1997 I studied NGC 3195 under the light
of a waxing gibbous Moon with the 20-inch f/13.5
Zeiss reflector at Auckland Observatory and with
its 4½-inch finderscope. The planetary was
virtually stellar in the finderscope, though it
swelled slightly with an increase in
magnification. The view was different through
the 20-inch. Despite the moonlight the planetary
displayed a robust, elliptical inner ring with a
swollen eastern lip. The ellipse is oriented
roughly north-south. It has a pale aqua inner
annulus that floats in a fainter sea of light whose
visual fabric appears rippled, like leathery skin;
but this detail was highly suggestive. I had no
problem seeing the 15th-magnitude central star at
686x, but I am not aware of anyone else who has.
Many ama-
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