evening, Mr. Barbee. On
February 1, 1786
William Herschel, discovered a rift of emission nebulosity due south of the
star Alnitak (Zeta Orionis) in Orion's Belt.
When it was omitted from the New General Catalogue, but later added to
the Index Catalogue as IC 434, nobody thought much about it.
That is, until 102 years later, when the American astronomer Williamina
Fleming noticed a small silhouette in front of it on a photograph of the area
taken at Harvard College Observatory. Edward
Barnard later cataloged that patch of dark nebulosity as Barnard
33, but most of us know it today as the Horsehead Nebula.
Since then, countless photos of the Horsehead have been taken, and while
many observers have tried to see the Horsehead directly, few have succeeded.
mission, should you choose to accept it, is to find the Horsehead for yourself
with your own binoculars. This
article will self-destruct in 5 seconds. Good
Above: Winter star map adapted from the book Star
Watch by Phil Harrington
Okay, I'm kidding about the self-destruct part, but not about
seeing the Horsehead through binoculars.
Last October, I received an e-mail from CN member Buddy Barbee asking if
I might relate my experiences with seeing the Horsehead Nebula through
binoculars. I'm happy to oblige; in
fact, I do just that in my new book, Cosmic Challenge (2010: Cambridge
University Press). Seeing the
Horsehead through giant binoculars is one of the most demanding tests in chapter
4, “Small Scope Challenges: Giant Binoculars, 3- to 5-inch telescopes.”
those who may have read my first book Touring the Universe through Binoculars
(1990: John Wiley and Sons), you will know that in there I say that "the
Horsehead Nebula…is too small and faint to be visible in binoculars."
I reasoned that it's tough enough to find it through large backyard
telescopes, let alone binoculars.
Well, that was before the 1991 Winter Star Party in the
some time observing alongside Tom Lorenzin, a talented astronomy author and
observer from North
I found out that I was wrong. Tom
showed me that the Horsehead is indeed visible in giant binoculars!
Above: Finder chart for this month's Binocular Universe.
Chart adapted from Touring the
Universe through Binoculars Atlas (TUBA), www.philharrington.net/tuba.htm
Here's how we did it.
First, we were in an ideal observing site.
The Keys' crystal clear skies and Orion's height above
the horizon certainly made a big difference.
Next, he taped a pair of hydrogen-beta line filters to
the eyepieces of his 10x70 Fujinon binoculars.
Finally, we made sure that Alnitak was just outside the
northern edge of the field, while nearby Sigma Orionis was
toward the western edge.
Then, with a detailed chart of the area at our side, we
looked for a close-set pair of 8th-and 9th-magnitude stars near
the center of the field.
These coincide with the leading edge of IC 434, the
emission nebula that lights the Horsehead from behind.
With Tom's help, it took
me only a few minutes to pick out both nebulae.
Of course, the Horsehead was very small, looking like the
silhouette of a thumb viewed from a few dozen feet away.
Tiny, but it was unmistakably there.
Give it a try and let me know how you make out!
If this challenge was a little too demanding,
then let’s try for something a little easier (but still
demanding enough to be included in my book).
In chapter 3 (Binocular Challenges), I challenge readers
to spot the reflection nebula M78 through more traditionally
Like the better known Orion Nebula, M42, M78 belongs to a vast
expanse of hydrogen gas called the Orion Molecular Cloud
currently wafting across the constellation.
While the hydrogen gas in M42 is being ionized into
fluorescence by ultraviolet energy emitted by the many stars
embedded within, M78 is visible only by reflecting the light
from nearby suns.
The starlight reflects off the grains of interstellar dust
scattered throughout the cloud, creating a reflection nebula.
To see objects like M78, we need a reasonably
dark, transparent sky.
Actually, I find M78 to be an excellent test of a winter
sky's quality. Under
a sky with a naked-eye limiting magnitude of 4.5, M78 is barely
visible through my 10x50 binoculars as a small, very faint blur.
Improving conditions to a naked-eye limiting magnitude of
5.5, M78 becomes much more obvious when the same binoculars are
aimed its way. The
oval cloud appears punctuated by a brighter, slightly offset
core. Although the
overall appearance reminds many of a faint comet, the brighter
"nucleus" is actually a pair of close-set 10th-magnitude stars
that are embedded within the cloud.
Despite the fact that the ultraviolet radiation emissions
from these stars is not enough to turn the cloud into an
emission nebula, their visible light is sufficient to light up
the multitude of dust grains within.
M78 is barely visible through the author’s 10x50
binoculars as a small, very faint blur along the
left edge of this sketch.
The three Belt stars, along with many
other members of Collinder 70,
line the right
North is up.
the author's new book,
Here is one final target this month that I
know every reader has seen a multitude
of times. No challenge here; in
fact, it’s visible easily to the naked eye.
You just may not have realized what you were look at.
I’m talking about the Belt of Orion.
All three of the Belt stars, along with another hundred or so fainter
suns, belong to an open star cluster known as
Collinder 70 (abbreviated Cr 70 on
the map above). The Belt Cluster was
not recognized as such until research conducted by the Swedish astronomer Per
Collinder (1890-1974) showed that the stars were all about the same distance
away and moving in the same direction through our galaxy.
Many of the 471 open clusters that Collinder included in his 1931 catalog
are too large and sparse to appreciate through most telescopes, but are perfect
Most of the stars in the Orion Belt Cluster shine brighter
than 9th magnitude, bringing them within range of 50-mm binoculars from suburban
skies. When you look their way,
consider that those stars are probably less than 10 million years old.
That's very young compared to our 4.5-billion year old Sun, but much
older than the stars in the Orion Nebula, which date back no more than 300,000
Overall, Collinder 70 looks football-shaped, with the three
Belt stars marking the ball's length.
There is also a distinctive S-shaped chain of 11 faint stars snaking from
Mintaka, the Belt's western star, to Alnilam at its center.
I like to think of them as stitching on the football!
So, there we have a couple of binocular tests and one easy object that will
hopefully push you out the door on these cold midwinter nights.
Looking for other objects to view?
Here are a few visible within this month’s Binocular Universe window.
If you spot any of these tough objects, I'd love to hear
about it. Send an e-mail to me at
firstname.lastname@example.org with particulars, or with any comments and
suggestions you might have for this e-column.
And be sure to print the
PDF version of this column to bring outside with you.
Click on the 'Download this Document' link at the top of this page
to download the PDF file, which you may print or save for future use.
Next month, we return to enjoy more of the magnificent winter
sky. Until then, remember that two
eyes are better than one.
About the Author:
Harrington is the author of Touring the Universe through Binoculars.
Visit his web site at www.philharrington.net
for more binocular targets visible this month.
Phil Harrington's Binocular Universe
is copyright 2011 by
Philip S. Harrington. All rights
reserved. No reproduction, in whole
or in part, beyond single copies for use by an individual, is permitted
written permission of the copyright holder.