Sky and Telescope - July 2017 - 38
p WHITHER THE WINGS This unfiltered view of Abell 79 was captured
through a 27-inch f/4.2 Newtonian reflector at 419×. Although aperture
helps, the author recommends using an O III filter to observe the uneven
surface brightness. Deep-sky images suggest that this planetary has
wing-like extensions, but they're very difficult to find visually.
p IMPOSTER The 13th-magnitude star shining near the center of Abell
82 is not responsible for the dumbbell-like shape of this planetary.
Rather, it's caused by the 15th-magnitude star 18 arcseconds to the
northwest. This sketch shows the view through the eyepiece of a 16-inch
f/4.5 Newtonian reflector at 150× with an O III filter.
critical mass and ignited fusion into carbon and oxygen. This
"ﬁnal helium ﬂash" ejected hydrogen-deﬁcient clumps inside
the old planetary. The star's temperature decreased, and it
returned to the AGB. Abell 78's born-again event is thought to
have occurred between 600 and 1,100 years ago.
On deep images, Abell 79 is an unusual elliptical ring
with extensions that morph into thin outer arcs or wings.
The orbit and interaction with the binary central star played a
crucial role in sculpting its bipolar morphology. This celestial butterﬂy hovers in a Lacerta star ﬁeld, 2.7° southeast of
4.2-magnitude Epsilon (ε) Cephei.
Through an O III ﬁlter at 115×, Abell 79 is an irregular oval
roughly 50″ × 40″ and it dips slightly in brightness towards the
center. The rim was a bit uneven and slightly more concentrated on the southeast side, but there was no evidence of the
wings. A couple of 14th- and 15th-magnitude stars cling to the
south side, and a similar star is pinned against the east edge.
Abell 81, also known as IC 1454, was originally discovered by accomplished British amateur William Denning in
J U L Y 2 0 1 7 * SK Y & TELESCOPE
1891 while he was comet hunting in the northern reaches of
Cepheus, 3.9° northwest of 3.2-magnitude Gamma (γ) Cephei.
Using his 10-inch reﬂector, Denning reported ﬁnding "rather
a difﬁcult object, except on a good night, though I picked it
up with a power of only 40. It is noteworthy as being situated
in the midst of a region containing very few nebulae."
A glaring 7th-magnitude star is parked 4′ east, but the
O III ﬁlter suppressed the star and revealed a faint 30″ disc.
Using a narrowband ﬁlter at 225×, the planetary appeared
fairly bright with a crisply deﬁned periphery. A relatively thick
rim enclosing a small, weaker center formed a delicate smoke
ring. Two 14th-magnitude stars are just off the northeast
edge, and a 13.4-magnitude star rests 1′ southeast.
Abell 82 lies 3.7° southwest of 2.4-magnitude Beta (β)
Cassiopeiae (Caph), the western star in the constellation's
distinctive W asterism, and 1.5° west-northwest of the
gorgeous open cluster NGC 7789 ("Caroline's Rose"). The
planetary was faintly visible unﬁltered as an irregular, diffuse
patch, roughly 1.5′ across. When I attached the O III ﬁlter,
the outline sharpened up and the contrast increased considerably. Images display an apple-core body with lobes extending both northwest and southeast (a mini-version of M27),
though visually only the northwest end seemed enhanced.
A 13th-magnitude star is superimposed just southeast of
center and masquerades as the central star. A more careful look disclosed the 15th-magnitude central star only 18″
to its northwest. I later checked the professional literature
and found the ionizing source is somewhat of a mystery. The
15th-magnitude star turns out to be a K0-type orange subgiant, and the true central star is likely an invisible companion.
Abell 84 is tucked into the southwest corner of Cassiopeia
less than ½° southwest of a 6.5-magnitude star and centered
within a 12′ pentagon formed by ﬁve 10th-magnitude stars.
An 11th-magnitude star abuts the east edge - look for a dim
glow spreading to its west.
I found the best view using a combination of 115× and an
O III ﬁlter, which yielded a 4-mm exit pupil. The moderately
p DIMMER YET Abell 84 is a ghostly apparition in the eyepiece. Look
for the 11th-magnitude star on the east edge of the shell. The faint nebulosity extends west and southwest of the star.
SK E TCHES: U WE G L A HN (2); A BELL 84: SH A RON K EMPTON & K A REN BRISTER / A DA M BLOCK / NOAO / AUR A / NSF