Sky and Telescope - January 2017 - 63

Mel Bartels noticed this interstellar material (often called
"Integrated Flux Nebulae" or IFN by amateur astronomers) the
ﬁrst time he pointed his brand-new 6-inch f/2.8 Dobsonian
at the Pleiades, which also happened to be ﬁrst light for his
wonderful telescope. For the ﬁrst time he saw the Pleiades in
context, and suddenly the dusty environment was impossible
not to see. He dubbed the nebulosity the Pleiades Bubble.
I saw it through his new scope at the 2014 Oregon Star
Party - and it was a really cool sight. I was in the ﬁnal
stages of building an 8-inch f/3.3 Dob, and as soon as it was
ﬁnished and I got it under a dark sky, I went looking for the
Bubble. To my surprise, it didn't jump out like it had in Mel's
scope. But after placing the bright stars of the cluster to one
side of the ﬁeld of view (FOV) I couldn't miss it.
The 2.7° true ﬁeld of view (TFOV) my 8-inch produces
with a Paracorr 2 and 21-mm Ethos eyepiece isn't quite large
enough to frame the Bubble adequately while the cluster sits
in the center of the ﬁeld, making it more difﬁcult to see.
Mel's 6-inch, on the other hand, has a 4.2° TFOV with the
same P2/21-mm Ethos combo, which frames the Bubble perfectly. Chuck's 4-inch f/5.5 APO refractor mentioned above
produces a nearly identical 4.3° TFOV.
I put it on the 2016 Oregon Star Party advanced observing
list, and the people who gave it a go were delighted.

That said, the wider the ﬁeld of view for a given aperture,
the easier it is to see the nebulosity. A wideband ﬁlter may
boost contrast a little, but a narrowband nebula ﬁlter won't
help because you'll be looking at reﬂection nebulae. The 115
million-year-old age of the Pleiades makes them too old to
have retained any of their natal nebulosity: the dust and gas
associated with and highlighted by the cluster's stars is interstellar material simply passing through and being illuminated
by the Pleiades. This moving material includes the Merope,
Alcyone, Electra, and Maia nebulae as well.
A note of caution: the brighter Pleiads usually show a circular glow around them through a telescope, but sometimes
that's just irradiation, or diffraction from dirty or damp
optics. Check a nearby star of similar brightness to see if the
same effect is visible - and make sure your eyepiece isn't
fogged over. Chances are you'll see a glow around Merope,
Maia, Alcyone, and Electra no matter what, so you're looking
for a glow that's larger than you see around the comparison
star you chose. The Merope Nebula, NGC 1435, is the brightest, so concentrate your gaze there ﬁrst.
qCAREFUL PLACEMENT The author used an 8-mm Plössl eyepiece
with his 28-inch f/4 telescope to make this sketch of IC 349. Placing
Merope just outside the field of view when the nebula was between
Merope's diffraction spikes made this observation possible.

Seeing the Classic Pleiades Nebulosity

qSTELLAR SPECTER The ghostly streamers in this Hubble Telescope image show
the effect of Merope's light on the reflection
nebula IC 349. The cloud's smallest particles,
slowed by the star's radiation, are left behind
at the lower left of the frame while larger
particles continue toward Merope's brilliant
lure. The rays of light at the upper right are an
optical artifact introduced by the telescope.

As for any faint nebulosity, you need dark and transparent
skies for a successful observation. Next is a wide-ﬁeld-of-view
telescope. You don't need a super-wide-ﬁeld telescope like
Mel's to see the classic Pleiades nebulae, but you do want to
use a telescope/eyepiece combination that gives at least a 1.5°
TFOV to see them well. It's my guess that almost anyone with
access to a dark sky and a wide-ﬁeld scope will see the Bubble.

Star magnitudes

IC 349: N ASA / HUBBLE HERITAG E TE A M (STSCI / AUR A); SK E TCH: HOWA RD BA NICH

5h 00m

4h 30m

3h 30m

3
4
5
6
7

4h 00m

+25°
M45
1435

+20°

ε
α

Aldebaran

TAURUS
Hyades
γ

+15°

π
λ

s k y a n d t e l e s c o p e .c o m

* JANUARY 2017

http://www.skyandtelescope.com

Sky and Telescope - January 2017

Table of Contents for the Digital Edition of Sky and Telescope - January 2017