SKY_September2014.pdf

SkyandTelescope.com September 2014 67

42 & 45 Orionis42 & 45 Orionis, sep. 4.2′ (ESE). In Orion’s Sword.

42 Ori: mag. 4.6, B1V, 900 l-y

45 Ori: mag. 5.2, F0III, 360 l-y

Very diffi cult. R.A. 5h 36 m, Dec. –4.8°

Theta OrionisTheta Orionis, sep. 2.2′ (NW). In Orion’s Sword.

Theta^2 : mag. 5.0, B1, 1,400 l-y

Theta^1 : mag. 5.1, B0.5V, 1,400 l-y

Extremely diffi cult. R.A. 5h 36 m, Dec. –5.4°

Iota OrionisIota Orionis, sep. 8′ (SW). In Orion’s Sword.

Iota: mag. 2.8, O9III, 2,300 l-y

Σ 747: mag. 4.7, B0.5V, 1,600 l-y

Moderately diffi cult. R.A. 5h 36 m, Dec. –5.9°

The familiar Sword of Orion is a complex

and fascinating area in binoculars and

telescopes. But did you know that each of

its three brightest stars is a challenging

naked-eye pair?

The northern pair consists of 42 and 45

Orionis. They’re embedded in a very faint

nebula for telescopes under dark skies.

The toughest is Theta^1 and Theta^2 in the

brightest part of the Great Orion Nebula;

they’re the closest pair in this entire list,

very faint, and they contend with the nebu-

losity and other stars in the immediate

area. I’ve never been able to split them, but

it might just be possible for someone with

exceptional eyesight and observing skills.

At the south end of Orion’s Sword is the

least diffi cult pair: bright Iota Orionis and

its neighbor Struve 747. The latter is a lovely

binocular double, magnitudes 4.8 and 5.7,

separation 0.6′.

Zeta CorviZeta Corvi, separation 6′ (WNW)

Zeta: mag. 5.2, B8V, 420 l-y

HD 107295: mag. 5.9, K0III, 400 l-y

Moderately diffi cult. R.A. 12h 21 m, Dec. –22.3°

Jumping forward into the spring sky, Zeta

Corvi and its companion lie within the

four-star “sail” pattern of Corvus. This con-

stellation is never very high, and the Zeta

double is a challenge for its faintness.

I often imagine myself sharing the sky

with our pre-technological ancestors, who

only had their unaided eyes with which to

explore the stars and fi nd these pairings.

I imagine that they must have found this

pursuit fascinating too. ✦

Jerry Lodriguss is an author, professional

photographer, and educator who writes about

and teaches astrophotography. For more of his

images of the double stars in this article, see

http://www.astropix.com/doubles.

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NakedEye_Doubles.indd 67 6/29/14 1:42 PM