Ophiuchus - Orion


A group replete with magnificent fields and clusters. It lies within the "Winter Triangle" of Sirius, Procyon and Betelgeuse, and contains a peculiar binary called Plaskett's Star, famous for being the most massive stars known. Each component of this peculiar double is 60 times more massive than the Sun. Most stars have masses of between 0.1 and 10 times the Sun's. Plaskett's star is of magnitude 6 and its position is given in the object index in the appendices.

Groups of stars

1. 12 (6.0), in the cluster NGC 2244, is surrounded by many brilliant formations.

2. 8 and 10. Sweep between these stars where you will find a bright group shaped rather like the constellation of Lyra.

3. 7(5.1). In a beautiful region.

4. Large triangle of 13, 15 and 17. Good sweeping here.

5. 06h 49m, -02. Group of bright stars extending to 13 (4.5).

Wide doubles

07h 14m, -10. Small triple, near the cluster NGC2353.

δ This 4.1m star makes a wide pair with 21.

Close doubles

Σ1183. A rather difficult, isolated pair. Mags 6 and 8, distance 31".

P.218. A faint pair in the central plane of the Galaxy. Mags 8.0 and 8.2.

P.219. A pleasant coloured pair of 6.5 and 8.3; 91" separates the faint star from its brighter blue primary.

P.223. A beautiful yellow and blue double of 6.8 and 7.0m. It can be found by drawing a line from ζ through 27 (5.1, orange) and prolonging it twice the distance.

Variable stars

U (5.6-7.3) An excellent star for the beginner, with good variations in a reasonable time. This member of the RV Tauri class is one of a little rectangle near a. The other members are 6.0, 6.6 and 7.0. Observe it once a week.

X (7.3-9.2) Another star giving good "value for money". A chart is supplied.

RV (6.8-8.3) A deep red star best found from the 6-7m arc a couple of degrees North. It lies between two stars of 6.5 & 7.1, and has a 7.7m neighbour.

RY (7.7-9.2) Another red variable, but with few good comparisons.

SU (7.7-9.0) A star of the rare spectral type S, 1 South of alpha. Take care to separate SU from its companion of 8.7 to the S. Just to the N. is a useful little triangle of 8.3, 9.0 and 9.0.

Clusters and Nebulae

NGC 2244. A brilliant cluster containg some bright coloured stars.

NGC 2343. Large instruments may show several little stars in this cluster.

NGC 2264. Appears as bright in the centre, with a prominent star to the South.

M.50 (NGC 2323). A large cluster, partially resolved in 20x70s.

NGC 2353. A really fine object, showing several stars in binoculars.


A really vast group, containing relatively few bright stars to the eye, but revealing many beautiful sights to the binocular lenses


Groups of stars

1. The yeds , or δ and ε. Fine sweeping around these stars, whose full names are Yed Prior and Yed Posterior. Imaginative or what?

2. Beautiful sprinkle around 19 (6.0).

3. Another neat group is near the 4.7m υ.

4. The naked-eye T-shaped asterism of 66, 67, 68 and 70; this used to be a separate constellation called Taurus Poniatowskii back in the days when influential patrons of scientists were being elevated to realms celestial! A beautiful part of the sky.

5. θ. In a region of numerous bright stars, clusters and dark nebulae.

Wide doubles

72. Has two companions, one of which is orange.

14. This has an attendant to the NW.θ. Note the orange star of 6.6m near this object.

Close doubles

Σ2166. A rather close pair (26") near Rasalhague.

53. An easier pair of magnitudes 6 and 7, 41" apart.

67. 55" apart, this is hard due to the 9m companion.

ρ. Binoculars reveal two companions. This star is in a large complex of dark nebulae which abound in this area. Best seen at high altitude and in dark skies.

OΣΣ 164. A faint pair 50" apart, readily found between 71 (4.7) and a curving line of bright stars.

Variable stars

X (6.5-9.0) A bright LPV, this is near a large bright parallelogram. Note a little triangle just E, of 7.3,7.2 and 7.1. Maxima of this star are given in the appendices.

V533 (7.0-8.0) A red star near ζ Serpentis. A large triangle of 6.5, 7.3 and 8.2 to the North can be used to estimate it.

V1010 (6.1-6.8) A chart is provided for this bright eclipsing binary.

Clusters and Nebulae

IC 4665. A really magnificent sight in binoculars, which will show over a dozen stars. An easy naked-eye object.

NGC 6633. Another marvellous cluster. A rather V-shaped group of many stars with an irresolvable glow behind them.

M.12(NGC 6218). A globular cluster, of which class there are many in Ophiuchus. It lies between two 6m stars.

M.10(NGC 6254). Another globular. A nebulous point in 6x30's.

M.19(NGC 6273). Yet another globular, as are M.9, 14 and 62. Try them all.


What can one say about Orion? The swordsman of the sky overwhelms us with his brilliant stars whether we use either naked eye or optical aid. The whole constellation teems with interesting objects - and is one of those rare instances in which the stars in a constellation really are, at least for the most part, connected with each other. Many wisps of nebulosity, and not just in the region of the famous nebula, either. Search out the whole constellation for these delicate objects when you have a suitably transparent night.

Groups of stars

1. The "shield" repays sweeping, even with the smallest glasses.

2. λ (3.7) forms a wide triple with φ1 and 2, with a pretty little straight line of three close by. Some nebulous gleams here.

3. Small arc below ξ (4.4) terminating in the cluster NGC 2169.

4. 71. One of a bright semi-circle.

5. Brilliant trapezium of 21, 23, 25 and ψ . Many bright stars here.

6. Sweep along Orion's belt, noting another fainter and less regular line to the South.

7. The equally famous sword is one of the most beautiful parts of Orion; the powerhouse of the whole group, if you like. Note two small sprays near the Nebula, M.42.

8. 56, 59 and 60. Members of a bright but isolated group. 59 is an easy double star, and 56 is orange.

Wide doubles

π1. A wide triple lies closely SW, of 6.1, 6.8 and 7.6. See if you can see any colour in the brighter stars.

72. A 5th-mag star with two yellow associates. Small group to the N.

π3 The lucida of the shield has two attendants which form a right-angle.

π5 Forms a contrasted wide pair with the red star 5 Orionis.

ζ Between this star and gamma Monocerotis is a wide triple of 6.0,6.2 and 7.1.

Close doubles

OΣΣ 58. Magnitudes 6 and 9, separation 89". One of a quadrangle.

Σ627. Easy to find, but hard to split at only 21".

23. One of group (5), this pair appears to me both white, though it is supposed to be yellow and blue. What do you think? Distance is 32".

δ. An easy pair, more definitely coloured, with a reddish secondary.

Σ747. A beautiful object near the Orion Nebula. 36" apart and both white.

Σ855. A more testing object of mags 6 and 7, 29" distant.

Variable Stars

U (6-12) A red Mira star which can become quite prominent, and which is very easy to find and estimate near maximum (see appendix). It is close to a bright trapezium, led by the 4.5m star χ1; the other stars are of 5.8, 6.0 and 6.6.

W (5.9-7.7) This deep red star is well-served with comparisons, including 21 (5.5) and a 6.3m just S. of rho. Directly between π5 and 6 is a fainter star of 7.9m. Use small glasses on this variable, otherwise it appears too red.

RT (8.1-8.9) A chart is supplied for this red variable.

BL (6.3-6.9) This red star on the border with Gemini is one of a quadrilateral. Use the Northern members of 6.5 and 6.8 for comparisons.

BQ (6.9-8.9) There is a line of stars to the NE of 6.9, 7.5, 8.6 & 8.9. A good star to follow, with a decent range in light.

KX (6.9-8.1) This, along with NU, V359 and V372 below, appears on the chart here. All these stars are eruptive variables, associated in some way with the Nebula; young, and recently-formed out of the vast cloud of gas they inhabit.

NU (6.5-7.3) See above.

V359 (6.9-8.1) See above.

V352 (7.4-8.9) As a relief from nebular variables, try this red star, which is in a line of four. West to East, they are: 7.5, 8.4, V352, 9.0.

V372 (7.8-8.5) See above.

Clusters and Nebulae

M.42(NGC 1976). The great Orion Nebula is easy with the naked eye, and binoculars of whatever size, but the larger the better, give an impressive view. The diagram under KX above shows the area in close-up and includes several bright representatives of the class of Nebular variables. One has to be careful in this area, as there are so many variable stars here that you never know if your comparison stars are variable themselves!

M.43(NGC 1982). Visible as a condensation around NU Orionis.

NGC 2169. A cluster visible as a misty patch.