Sky and Telescope - July 2016 - 35

ability to see them depends on how well your instruments handle the faint stars of these clouds.
While some dark objects - such as Barnard's E and
B133 - are within binocular range, a basic beginning
demands that your telescope be able to pull in 13th- to
15th-magnitude or fainter stars in relatively large ﬁelds
of view. The 13th-magnitude limit is provided by telescopes with single-digit inches of aperture. Besides my
trusty 2-inch f/8 refractor, I've also used a homemade
6-inch f/6 reﬂector and an Orion 120-mm (4.72-inch)
f/5 refractor. The 15th-magnitude limit will generally
require instruments with inches of aperture in the
double digit range. I've used a 12-inch f/5 reﬂector and
a 20-inch f/5 reﬂector, as well as various professional
instruments of larger sizes, with great success.
Let me know your impressions of these wonderful
and mysterious dark objects. From which dark sites and
with which scopes were you able to observe them? Enjoy
the view of the dark side of the summer Milky Way! ✦

LDN 676
LDN 677

JIM THOMMES

LDN 673

Richard P. Wilds is a member of the American Astronomical Society, Division for Planetary Sciences. His latest publication is Bright and Dark Nebulae: A Pocket Field Guide
(Springer, 2016). Richard can be reached at astromaster@
att.net.

FRACTURES AND FISSURES To locate a dark nebula, search
for an "absence of light" that marks the central part of the
structure. From there, work to tease out the extensions and fragments at the nebula's edge.

B135
LDN 581

star plow into surrounding nebulosity; the interaction
causes the light of hydrogen atoms and sulfur ions to
glow. Nearly adjacent to LDN 673, HH 32 is one of the
easiest HH objects to capture. Slew just 10′ southeast of
HD 181384 to ﬁnd it. There are several 11th-magnitude
and fainter stars in close proximity, and all are involved
in some faint nebulosity, but HH 32 can be seen as a
"ﬁnger extension" to the south of the 11th-magnitude
variable star V1352 Aquilae. Their proximity gives the
appearance of a double star that requires higher magniﬁcations than I usually apply around dark nebula regions.
The excitement for me is knowing that I'm looking at a
relatively close dark nebula and seeing in it evidence of
newly forming protostellar planetary systems much like
our own solar system (only much younger, of course).

LDN 577

15 Aql
B136

B328

LDN 580

B132
LDN 574

Be aware that dark nebulae can be seen with many different telescopes - as long as the observer is willing to
travel to an extremely dark location. For the most part,
suburbia will not work. Dark nebulae are visible because
they front brighter, more distant objects. In the case of
those in Aquila, the "brighter, more distant objects" are
provided by the star clouds of the Milky Way, and your

DAN CROWSON

What to Use and When to Use It

GLOOMY GATHERING This LRGB image, processed from data gathered
during a 240-minute total exposure with a 90-mm f/6.7 apochromatic refractor and imaging CCD reveals the dark objects in the vicinity of 15 Aquilae.

Sk yandTelescope.com July 2016

http://www.SkyandTelescope.com

Sky and Telescope - July 2016

Table of Contents for the Digital Edition of Sky and Telescope - July 2016