The Caldwell Objects

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reflector at 100x NGC 3242 resembles the eyeshaped
logo used by the CBS television network.
Indeed, the "CBS Eye" moniker has caught on fast
and is now popularly employed as much as the
"Ghost." The more streamlined name, the Eye
Nebula, didn't fare so well because there is yet
another Eye Nebula: the Cat's Eye (Caldwell 6), a
bright planetary in Draco.
Smyth, who is infamous for his truly "colorful"
descriptions of double stars, did not note
NGC 3242's subtle blue or green hue, which so
many amateurs enjoy today. I believe that since
William Herschel did not attribute a particular
color to NGC 3242, neither did Smyth. John
Herschel first specified the nebula's color, seeing
it as a "decided pale blue; at all events a good
sky-blue." The Rev. T. W Webb found it "of a
steady pale bl[ue] light."
Heinrich Louis d'Arrest didn't see color in
NGC 3242 but made out two "nuclei" near the
limb. And Angelo Secchi, who studied NGC 3242
at 1,000x, saw "within a circular nebulosity two
clusters, connected by two semicircular arches of
stars, forming a sparkling ring, with one star on
the hazy ground of the centre." William Huggins
acquired a spectrum of the "Ghost," and this
spectrum led him to conclude that Secchi's ring is
made of gas, not solid matter.
Curiously, of all these great observers, only
Secchi saw the planetary's central star. I say
"curious" because in photographs the star blazes
at magnitude 11.3. Granted, most visual
estimates place it closer to 12th magnitude. Still,
the central star should be obvious at the eyepiece
of a fairly large telescope. Why, then, did John
Herschel — who observed NGC 3242 from the
Cape of Good Hope on four different occasions
with an 18¼-inch reflector — not record it? After
all, John, like his father, tried to resolve all
nebulae into stars.
The central-star mystery lives on. I have seen
very few accounts of amateurs seeing
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NGC 3242's central star through small telescopes.
But consider the following sequence of notes
from Houston's "Deep-Sky Wonders" column. In
1947 Houston said the central star was 11th
magnitude. In 1971 he reported seeing the" 11.5magnitude"
central star in a 6-inch at 150x. In
1978 he wrote that the central star is "much
fainter" than photographic magnitude 11.4. And
in 1984 he said that California amateur Tokuo
Nakamoto estimated the star as magnitude 12.5.
That same year "Scotty" was at the eyepiece,
looking at NGC 3242 after having cataract
surgery. This is how things looked through a 5inch
"apogee" scope at 39x: "The central star was
easily seen with my eye that had its lens removed
during cataract surgery. The star appeared
almost as bright as the entire planetary in this
eye, while it was hardly visible at all in my
normal eye. This was surely due to a greater
amount of ultraviolet (UV) light reaching the
retina of the eye without its natural lens. Central
stars in planetaries are generally strong emitters
of UV." In their Observing Handbook and Catalogue
of Deep-Sky Objects, Christian Luginbuhl and
Brian Skiff record the central star's magnitude as
11.9, while The Deep Sky Field Guide (1993) lists it
as 12.1. James Mullaney also has noticed the
central star's "strange variations over the
Deep-Sky Companions: The Caldwell Objects