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Southern Cross - March 2003

• COTM: Puppis by Michael Nelmes
• Some Puppis Doubles by Ross Gould
• Star Clusters & Nebulae In Monoceros by Jenni Kay

COTM: Puppis

Michael Nelmes

'They felled the pines on Pelion and shaped them with the axe, and Argus taught them to build a galley, the first long ship which ever sailed the seas. They pierced her for fifty oars - an oar for each hero of the crew - and pitched her with coal-black pitch, and painted her bows with vermilion; and they named her Argo after Argus, and worked at her all day long.'

Overhead in the early evening this month is Puppis, a constellation last seen in this column eight years ago. In days of old it formed the stern of Argo Navis, the ship in the ancient Greek tale of Jason and the Argonauts. Now divided into Vela the sails, Carina the keel and Puppis the poop deck, it's a good region for low power viewing, with a profusion of southern Milky Way open clusters. Charles Messier catalogued just three clusters here (M46, M47 and M93) during the late 18th century. However, with the advantage of southerly latitude, we Canberrans can reward ourselves with more by scanning along the galactic equator using nothing more than good binoculars.

To find Puppis, draw a line from Sirius to Canopus and look east of it. It's bordered by Pyxis, Carina, Pictor, Columba, Canis Major, Hydra and Vela, and although it has few bright stars - zeta (ζ), rho (ρ), pi (π) and tau (τ)(presumably following the order of Argo Navis, hence no alpha, beta etc.) being the brightest at mag. 2.3 to 3 - it's not too hard to find if you star hop from Sirius. The observations below were on a moonless night from Spence with a C14 Schmidt Cassegrain using, for the most part, a 2-inch 55 mm Plossl eyepiece giving 72x.

M46 (NGC 2437). RA 07 41.8, Dec. -14 49. A rich, magnitude 8 open cluster of some 150 moderately bright stars, with the apparent size of the Moon. The thing that sets M46 apart from other clusters is an interesting interloper: the planetary nebula NGC 2438 superimposed on its northern edge. Higher magnification shows this 1 arcminute, 11th magnitude nebula to be ring-like, with a star just off centre and another at its edge. Not to be missed.

M47 (NGC 2422). 07 36.6, -1430. Consists of brighter (up to magnitude 5), but fewer, stars than in nearby M46.

M93 (NGC 2447). 07 44.6, -23 52. Another open cluster of around 50 stars, magnitudes 8 to 13 giving it an integrated magnitude of 7 - borderline naked-eye. A smaller but brighter group than M46.

NGC 2477 07 52.3, -38 33. 'Splendid, rich'; (from Burnham), this open cluster is dense enough to appear like a diffuse globular. Slightly smaller in apparent size than the Moon.

NGC 2451 07 45.4, -37 58. One for small scopes, being diffuse and containing relatively bright stars without the background of faint ones that gives nearby NGC 2477 its beauty.

2 Puppis. A binary of magnitudes 6 and 7, with separation 15 arcseconds.

Cr 135 07 17.0, -36 50. A very loose association of bright stars. My notes refer to an attractive binary near Pi Puppis in this grouping, closely separated and of equal brightness [see Ross Gould's article below].

NGC 2440 07 41.9, -18 13. Planetary nebula, slightly dimmer than NGC 2438. The central star is magnitude 16.

Some Puppis Doubles

Ross Gould

The doubles here are a small selection of some of the brighter and more interesting from the 160+ I've observed in Puppis, all accessible to medium apertures (circa 20 cm). Observations were with 7" and 14" scopes.

HJ 3834 06047-4505 AB m6.0, 9.0 5.7" pa218 1995 F5

AC: m 6.0, 6.4 196" G0

7-inch 100x: three bright stars dominate a thin field; the AC pairing is very wide, both stars yellow, and the brighter has a fairly close companion, an easy neat little point near the primary (AB). AC pair is obvious in 8x50 finder.

DUN 23 06048-4828 m7.3, 7.7 2.6" 120 1999 G6

7-inch 100x: fine nearly even close yellow pair in a not very starry field; a nice object.

HJ 3905 06583-3525 m7.8, 9.7 14.7" 270 1991 Ap

I 66 (AB of HJ3905) 7.8 9.3 1.9' 253 1991

C14 70x: an obvious easy pair in a field with 4 bright stars, and scattered fainter ones in patterns. At 120x the main star is double, uneven and close, both stars white (I 66). Pi Pup 07171-3706 m 2.9, 7.9 69" K3, B9

C14 70x: dominating a field that includes some bright stars is this very bright orange star with a wide white companion, showing a hint of blue in contrast. A good field. There is a loose cluster here, Cr 135: the 10x70 finder gives a fine view of the cluster, with a main group of four stars; Pi is orange, the other stars white.

JC 10 07183-3644 AB: m4.7, 5.1 240". At 117" in PA 216 (SW) is pair CD: m 8.7, 9.2 at 3.0" pa212 1991.

C14 70x: two bright white stars have a less bright star making a triangle with them: it is a neat close pair, near even — elegant and nicely separated at 120x. JC 10 is also part of the Cr 135 cluster along with Pi Pup (above).

STF 1121 07366-1429 m7.0, 7.3 7.8" 305 1997 B6, B6

7" 100x: even easy white pair in the little cluster NGC 2422. At the western end of the cluster is STF 1120, an obvious uneven easy white pair [07 36.1 -14 30: AB-C mag. 5.7, 9.6: 19.8" 041 1974].

HWE 65 07523-3442 m5.1, 8.6 3.6" 270 1994 F5

7" 100x: a beautiful delicate pair - 'A' is bright and pale yellow, 'B' a tiny point beside it. Scattered field.

BU 454 08 15.9 -30 56 m 6.5 8.2, 1.9" 002 1997 G5

C14 120x: a fine field, with stars in wide pairs and patterns. The deep yellow BU 454 dominates - barely double at 120x, it is a fine fairly close uneven pair at 240x. Just north is an attractive arc of 8-11 mag. stars.

Star Clusters & Nebulae In Monoceros

Jenni Kay FRAS

There is a rich concentration of star clusters and nebulae around the area of the Rosette Nebula (N2237-9, 46). There are also some so-called "nonexistent" star clusters in this region, but I will hold over until next month to tell that story. Here there is a mix of open star clusters (OC), emission nebulae (BN), and reflection nebulae (RN), all offering interesting and impressive sights.

The following observations were made with either an 8" f/6 Newtonian or 12.5" f/5 Newtonian from my semi-rural home site in Lobethal, SA. The skies here have a limiting naked eye magnitude of 6.1, with the seeing rated at ANT II-III. I have also included an observation on the Cone Nebula (lies within NGC 2264) as seen through the 30-inch f/5 Newtonian from Riverton, SA. The skies here have a limiting naked eye mag. of 6.5.

IC 446 : 06 31.0 +10 27 (RN)

12.5" f/5 Newt. 105X: Obvious enough - relatively faint, relatively large, irregularly round, soft, nebulous glow around a 12 mag. star. 150X: Improved view - relatively faint, round, 1.5' in diameter, smooth glow with the star at the centre. The neb lies 49.0' NW of NGC 2264 : OC/BN.

IC 448 : 06 32.7 +07 19 (RN)

8" f/6 Newt. 80X: Very obvious - there is a very bright, 4.5 mag. star, showing a strong yellow colour, within a bright, hazy halo. The nebula stands out well. 120X: Similar view - very bright, round, 4.5' in diameter.

IC 2169 : 06 31.1 +09 56 (RN)

12.5" f/5 Newt. 105X: Requires care as the soft nebulous glow is very subtle. Firstly, there is a sweeping arc of four bright stars ranging from 8-10 magnitude, and around them there seems to be a very faint, milky glow. It is rather surprising that this nebulosity can be seen at all since in the wider region are extensions from the nearby Rosette nebula. The IC 2169 glow seems a little stronger around the two most northwestern stars of the four in the arc. 150X: No improvement. Lies 31.0' W NGC 2264.

NGC 2180 : 06 09.6 +04 43 (OC)

8" f/6 Newt. In my opinion, this is quite an unremarkable sight! There is no star cluster here per se, it appears more like an asterism of stars to me. There is one bright 9 mag. star with a long chain of stars curving around it. There are about 12 stars involved, with no central concentration, but well detached from the background sky. 120X: Similar view, and same impression - twenty stars involved, ranging from 10 - 12 magnitude, 10.0' east to west and 4.5' north to south.

NGC 2186 : 06 12.1 +05 27 (OC)

8" f/6 Newt. 80X: Obvious, soft and delicate collection of a few stars, small in size and well concentrated. The stars range in brightness from 11-13 mag. 120X: There are ten stars involved, but I suspect there are more that are lost in unresolved haze. The cluster is 4.0' in size and irregularly round in shape.

NGC 2202 : 06 16.8 +05 59 (OC)

8" f/6 Newt. 80X: Most unremarkable - a few stars in a group almost shaping a circlet. There are thirteen stars involved, ranging from 10 - 13 magnitude, and open in the centre. Not a visual star cluster per se, and hardly even rates as an asterism. 120X: Slightly improved where the star group is now contained in a smaller field of view and somewhat detached from the busy background sky. There are 15 stars involved in this group which is 5.0' in size.

NGC 2236 : 06 29.7 +06 50 (OC)

8" f/6 Newt. 80X: There are two stars, 12/13 mag. in a soft glow from very faint unresolved stars. 120X: Much improved - two stars surrounded by a small gathering of a few faint stars, fifteen in number, 13-14 mag. in brightness, and 5.0' in size. The cluster is spherical in shape, somewhat concentrated, and well detached. In general, the view is rather charming!

NGC 2237-9, 46 : 06 32.3 +05 03 The Rosette Nebula (BN)

8" f/6 Newt. 80X: Bright, very large, extends over two 49.0' fields of view. The nebula is smooth throughout rather than showing the rose petal folds, and the brightness in the nebula is uneven. The star cluster N2246 is involved, and here, the bright nebulosity is broken by a darkness at the centre of the rose.

NGC 2239 : see NGC 2237. The Rosette nebula.

NGC 2244 : 06 32.3 +04 51 (OC) associated with the Rosette nebula.

8" f/6 Newt. This large loose grouping of bright and faint stars lies within a dark break (appearing like a dark hole) in the Rosette nebula. There are some eighty stars involved, with a few bright 7th mag. stars mixed with 10 - 11 and fainter. Overall, the cluster is spherical in shape. 150X: Striking view - the stars are strewn across a dark background sky encircled by the bright nebula extending outwards. The cluster is 25.0' in size.

NGC 2245 : 06 32.7 +10 10 (RN) 12.5" f/5 Newt. 105X: Very obvious - bright, relatively large, fan shaped, or comet shaped hazy glow with a star at the NE tip. 150X: Improved - bright, 2.5' in size, brightest near the star. Overall, the nebula is very attractive. 20.0' east of N2264 (OC/BN).

NGC 2246 : see NGC 2237. The Rosette nebula.

NGC 2247 : 06 33.2 +10 20 (RN)

12.5" f/5 Newt. 105X: Obvious enough - there is a bright 8.5 star within a relatively faint, relatively large, round hazy halo. The star lies in the northern region of this nebulosity. 150X: Improved - relatively bright, irregularly round, 3.5' in size.

NGC 2251 : 06 34.7 +08 22 (OC)

8" f/6 Newt. 80X: Obvious - very irregular shape, more like an asterism rather than a star cluster per se. The stars stand out as a group being more concentrated than surrounding stars which are evenly spread out. Overall, the group is relatively large, loose, with twenty-five stars involved all similar in brightness at around 12 mag. Stars form one long, fairly straight chain on the SW side, and a curving chain of the opposite side, and overall, remind me of a cone-style sea-shell. Interesting! 120X:The group is 10.0' in size NW - SE x 3.0'. Overall, the star cluster, or asterism, is most attractive and certainly worthy of note.

NGC 2252 : 06 35.0 +05 23 (OC)

8" f/6 Newt. Another cluster which appears more like an asterism rather than a star cluster per se - the eye is drawn to a long and lanky group of stars seeming to form two long strings entwined like a piece of rope. Interesting, and worthy of note! There are 20 stars involved, all similar in brightness at 11-12 mag. 120X: twenty-five stars counted, with a size of 10.0' N-S x 3.0' E-W. Also worthy of note is a quaint, tight, triangle of three stars 25.0' to the east.

Many of the modern catalogues use the Gosta Lynga position (as noted above), but this places the centre of the cluster 10.0' too far to the east. A more central position would be 06 34.3 +05 20. At the Lynga co-ordinates there is no cluster, or concentration of stars seen by me.

NGC 2254 : 06 36.0 +07 40 (OC)

8" f/6 Newt. 80X: Obvious - small collection of a few faint to irresolved stars, appearing very soft and delicate in the bold and rich star field. Overall, the cluster forms a crescent shape, making it attractive and worthy of note. 120X: Improved view - there are six stars all similar in brightness at 13-14 mag. The cluster is well detached, well concentrated, with a size of 3.0'.

NGC 2259 : 06 38.7 +10 53 (OC)

8" f/6 Newt. 80X: The eye is drawn to a very soft glow to a little resolved, from the small gathering of a few loose, faint stars. 120X: Slightly improved - soft unresolved glow, but averted vision resolves ten stars, with more suspected. The stars range from 14 to fainter in magnitude. The cluster is 4.0' in size, spherical in shape, and somewhat concentrated. In the general, wider view, there is a very bright 6.0 mag. star 10.0' to the west, showing a strong yellow colour, and a light mix of 10-12 mag. and fainter field stars over a milky background from the outskirts of the N2264 nebula.

NGC 2261: 06 39.2 +08 44 ( B + RN) "Hubble's Variable Nebula"

8" f/6 Newt. 80X: Obvious - relatively bright, small, fan-shaped spot, with a star at the southern apex. Very attractive whole view - fairly rich star field being a good mix of 10, 11 mag. and fainter stars and this obvious nebula. 120X: Improved - almost resembles a comet in appearance with the star at the apex like a comet nucleus. Overall, the nebula is bright, and 1.5' in size.

NGC 2264 : 06 41.1 +09 53 (OC/BN)

8" f/6 Newt. This is a star cluster with very extensive nebulosity involved, where the nebula itself has two specific features known as the "Christmas Tree Nebula" and the "Cone Nebula". Overall, this complex nebula extends out to 2.0 degrees in size. On the star cluster: Large, loose collection of bright stars, with 15 Mon invol-ved, which resemble a large stellar association in appear-ance, rather than a star cluster per se. There are 25 involv-ed, ranging from 5-9 magnitude, with 15 Mon displaying a pale yellow colour. The cluster is a little elongated N-S, and 25.0' in size. The nebulosity is strong here as the cluster lies within the "Christmas Tree Nebula".

The Christmas Tree Nebula : There is a strong, hazy glow around 15 Mon which decorates the tip of the Christmas tree shape. From here the nebulosity stretches 8.0' to the SW to three bright stars that form the base of the tree. Between the tip and tree base the nebulosity is mottled, textured, and a little irregular. There is a very strong response to the OIII filter here and in the general, wider area. Also, 8.0' ESE of 15 Mon are three stars in a triangular shape, and these too are wrapped in a brighter, nebulous halo. 120X: No further detail seen. (12.5" f/5 Newt. Similar detail seen, but brighter and stronger.)

Cone Nebula : 12.5" f/5 Newt. 75% suspected, with a slight difference in contrast seen, but difficult to see any cone shape. 30" f/5 Newt; Riverton, SA: 120X: UHC filter - dark figure seen. At the northern tip of the cone there is a very small, nebulous knot. 240X: UHC filter - best view so far of dark, cone shape. A central position for this nebula is 06 41.0 +09 27.