SKY_September2014.pdf

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Sept 1

Saturn

Mars

Gary Seronik

Binocular Highlight

SkyandTelescope.com September 2014 45

Barnard’s E

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AQUILA

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Aquila’s Dark Secret

Dark nebulae are one class of deep-sky object that

doesn’t get enough attention. That’s not surprising

because appreciating them requires a diff erent mindset.

Instead of seeking light, you’re hunting for the absence

of luminosity. The other factor that works against dark

nebulae is that you need very good skies to have any

chance of seeing them at all. If you can’t see the Milky

Way easily, you’re out of luck. That’s because you need

the background glow of starlight to render these opaque

objects visible. Riding high in the sky this month, the

constellation Aquila provides both a rich swath of Milky

Way and one of the fi nest binocular dark nebulae.

The Charles Messier of dark nebulae was Edward

Emerson Barnard. Like Messier, Barnard started out

a comet hunter, but he’s best known for his work at

Yerkes Observatory, where he produced a photographic

atlas of the Milky Way. A byproduct of this eff ort was

his catalog of dark nebulae. Instead of M numbers, his

objects have B numbers — including Aquila’s B142 and

B143. Together, these opaque clouds are also known as

Barnard’s E, owing to their photographic resemblance to

the fi fth letter of the alphabet.

I can make out Barnard’s E fairly easily in my 10× 30

image-stabilized binoculars, provided the skies are dark

and clear. The E shape isn’t distinct, however — the

nebulae more resemble a pair of east-west elongated

blobs joined by a vague vertical protrusion. I can see the

dark nebula in my 15×45 image-stabilized binoculars too,

but it’s actually slightly more diffi cult. That’s because

the fi eld of view is a bit too constricted to include both

the nebula and enough of the surrounding Milky Way to

let it stand out. ✦

When

Late July Midnight*

Early Aug. 11 p.m.*

Late Aug. 10 p.m.*

Early Sept. 9 p.m.*

Late Sept. Nightfall

* Daylight-saving time.

NHSC layout.indd 45 6/23/14 12:18 PM