SKY_September2014.pdf

66 September 2014 sky & telescope

Spottable Pairs

OmicronOmicron^11 & Omicron & Omicron^22 Cygni Cygni, separation 61′ (NNE)

Omicron^1 : mag. 3.8, K2II, 900 l-y

Omicron^2 : mag. 4.0, K3Ib, 1,050 l-y

Easy. R.A. 20h 14 m, Dec. +46.8°

OmicronOmicron^11 & 30 Cygni & 30 Cygni, separation 5.6′ (NW)

Omicron^1 : mag. 3.8, K2II, 900 l-y

30 Cyg : mag. 4.8, A5IIIn, 600 l-y

Moderately diffi cult. R.A. 20h 14 m,Dec. +46.8°

The two Omicron stars in Cygnus, 5° from Deneb, are

so far apart that they’re a double only under the loosest

defi nition. The challenge here is Omicron^1 Cygni and its

much closer neighbor, 30 Cygni. Binoculars and tele-

scopes split Omicron^1 into an orange-red and bluish pair,

which make a lovely triple with white 30 Cygni.

Alpha Capricorni (Algedi)Alpha Capricorni (Algedi), separation 6.3′ (WNW)

Alpha^2 : mag. 3.6, G8.5III-IV, 105 l-y

Alpha^1 : mag. 4.3, G3Ib, 570 l-y

Showcase naked-eye double! R.A. 20h 19 m, Dec. –12.5°

The western tip of Capricornus is one of the loveliest

naked-eye doubles in the sky. Although they’re just an

optical pair, both stars are yellow giants, and both have

extremely faint telescopic companions.

SteropeSterope, separation 2.5′ (SE). In the Pleiades.

21 Tauri: mag. 5.8, B8V, 370 l-y

22 Tauri: mag. 6.4, A0Vn, 380 l-y

Extremely diffi cult. R.A. 3h 47 m, Dec. +24.6°

Altas & PleioneAltas & Pleione, separation 5.0′ (N). In the Pleiades.

27 Tauri (Atlas): mag. 3.6, B8III, 380 l-y

28 Tauri (Pleione): mag. 5.0, B8Vne, 380 l-y

Moderately diffi cult. R.A. 3h 50 m, Dec. +24.1°

The Pleiades contain two naked-eye challenge pairs. The

famous Atlas and Pleione are the legendary parents of the

Seven Sisters. I rank them as only moderately diffi cult, a

beautiful pairing amidst the other jewels of the Pleiades if

you can manage it. The Sterope (or Asterope) pair, on the

other hand, is very tight and very faint as well.

Theta TauriTheta Tauri, separation 5.6′ (NNW). In the Hyades.

Theta^2 : mag. 3.4, A7III, 150 l-y

Theta^1 : mag. 3.8, K0IIIb, 155 l-y

Showcase naked-eye double! R.A. 4h  29 m, Dec. +16.0°

Delta TauriDelta Tauri, separation 18′ (ESE). In the Hyades.

Delta^1 : mag. 3.8, G9.5III, 155 l-y,

Delta^2 : mag, 4.8, A2Vs, 160 l-y

Fairly easy. R.A. 4h 24 m, Dec. +17.6°

The Hyades contain two much easier targets. Theta Tauri,

near Aldebaran, is right up there with Alpha Capricorni

as one of the fi nest near-equal naked-eye pairs in the sky.

Binoculars show a color diff erence: orange and bluish.

In the opposite arm of the Hyades’ V pattern, the

Delta^1 -Delta^2 pair is fainter but much wider. Delta^3 Taur i,

twice as far to their northeast, outshines faint Delta^2 by a

half magnitude and forms an elongated triangle with the

closer Deltas.

CAPRICORNUS

Alpha

Vega

Beta

LYRA

Delta

Epsilon

NakedEye_Doubles.indd 66 6/23/14 12:17 PM