Sky & Telescope - June 2021 - 29

I consulted Steven J. Hynes's Planetary Nebulae: A Practical
Guide and Handbook for Amateur Astronomers and identiﬁed
several objects that would pass through my sendero - all had
magnitudes suitable for moderate-size telescopes (between 9
and 13). The only drawback was their southerly declinations
(as low as -44°), which might render them difﬁcult to see
because of atmospheric extinction, sky glow, and murk when
viewed in Houston skies. I nevertheless decided to pursue this
project - here was an opportunity to see some planetaries
possibly neglected by some observers.

ESO

Equipment and Protocols
I used my 7-inch Questar Maksutov-Cassegrain telescope to
view the nebulae presented here. I was unable to sit during
observing sessions because of the low declinations of my
chosen targets, but the pier for the telescope elevates so I
could stand comfortably with the eyepiece within easy reach.
The only restriction was that the fork-mounted Questar in
equatorial mode could only be aimed to about -45° declination before the tube collided with the base of the mount.
I selected four different eyepiece setups for these observations. They were as follows: I used a 34′ eyepiece ﬁeld at 80×;
a 25′ eyepiece ﬁeld at 106×; a 17′ eyepiece ﬁeld at 160×; and a
13′ eyepiece ﬁeld at 212×.
A O III narrowband ﬁlter is necessary for enjoying most
planetary nebulae - and I used one at some point for each of
the objects discussed here. When I use the ﬁlter, I pre-focus
on a nearby brighter star for the sharpest image possible. This
way, I can evaluate any disk the nebula may present. Another
tool is an eyepiece equipped with an occulting bar, which I
made by afﬁ xing a very thin strip of aluminum foil across the
ﬁeld stop. The bar can be rotated to any position.
The most important pieces of observing " equipment " I
have are my eyes. In 2008, I had cataract surgery in both eyes
and had acrylic lenses implanted. Along with greatly improved
visual acuity, another noticeable difference is that many
planetaries, which I previously described as greenish-gray or
green, now appear to be blue. Indeed, the Ghost of Jupiter
(NGC 3242) presented an electric-blue disk one evening. By
the same token, though, the star Beta (β) Librae still seems a
benign green to me, implying that the yellowing of my cataracts probably caused the greenish colors of the nebulae.
Years ago, I noticed that light pollution worked in concert with atmospheric pollution. When weather conditions
scoured the sky of smog, haze, and particulates, often a
period of relatively good seeing and transparency followed.
Picking those rare nights to observe improved the odds for
locating and viewing faint nebulae near the southern horizon, but of course the targets have to appear in the sendero
in order for me to spot them.
Most of the planetary nebulae observed in this exercise are
relatively bright (for this class of objects) and associated with
micro-asterisms and/or brighter stars, which made them
easier to locate. On the negative side, it required patience to
wait for the nebulae to clear the foliage and enter the send-

ero. Moreover, once diurnal motion carried the object out of
the corridor, it was generally lost for the year.

From Vela to Hydra via Pyxis
For a few evenings in May, NGC 2792 culminates in my sendero about 18° above the southern horizon for a few minutes.
This 11.6-magnitude planetary in Vela is around 13′ southwest
of a 6.3-magnitude star. At 80× I positioned the star in the
northeastern quadrant of the ﬁeld, installed an O III ﬁlter, and
was rewarded by a small (5″ to 8″) gray form near the center.
With the ﬁlter and at 160× the view in the eyepiece improved,
revealing a small, round, whitish disk. I didn't see the central
star nor any evidence of annularity. After I removed the ﬁlter
and refocused, I could still see the nebula with averted vision.
Shifting north in declination, I popped into Pyxis to view
the planetary nebula NGC 2818. It's associated with an
open cluster that - depending on source - carries the same
designation as the planetary (see S&T: Mar. 2021, p. 61).
On setting the coordinates for NGC 2818, I immediately
saw a suspicious area at 106×, along with a few stars of the
open cluster. Switching to 160× with ﬁlter, I conﬁrmed the
11.6-magnitude planetary. I saw it as a gray-white puff but
didn't make out its bipolar structure.
Heading back into Vela, I searched for NGC 3132, or the
Eight-Burst Nebula as it's also known. A relatively bright
magnitude of 9.2, large diameter, and high surface brightness
facilitate its detection. At 160× with the O III ﬁlter in place, I
saw the nebula as bluish-white with irregular edges. The disk
was elongated in the northwest-southeast direction, and I
suspected annularity. When I removed the ﬁlter, I noted the
displaced 10th-magnitude central star.

S SOUTHERN OWL NEBULA You can find this ethereal bubble, also
known as Kohoutek 1-22, in the southern reaches of Hydra. This image
was captured with the European Southern Observatory's Very Large
Telescope in Chile.
sk yandtelescope.org * JUNE 2 021

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Sky & Telescope - June 2021

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