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Southern Cross - March 2000

• Constellation of the Month - Lepus
• The Brilliant Star Clusters of Puppis

Constellation of the Month - Lepus

John Morland

Lepus the Hare is one of the ancient constellations to which Ptolomy assigned twelve stars. It is easily recognised as a trapezium of 4 main stars immediately south of Rigel and Saiph (the two stars forming the two knees of Orion). At the moment, face west shortly after twilight: Lepus is just left of Orion, that is, high in the sky. Lepus lies at the feet of its hunter, Orion, pursued by across the sky by Canis Major, the Big Dog. Lepus cannot match Orion's brilliance, but that is not say there aren’t some interesting objects for an amateur astronomer's eye.

A quick look through binoculars helps to identify the shape of the constellation ( I thought it looked like a flat capital I, or a cross section of an I-beam), where the double stars are, and the places where the fainter objects lie. Before putting the binoculars away, have a look at gamma Leporis (RA 5h 44m, Dec -22°). This is a binocular double 277 light years away, consisting of a yellow star (3.6 mag.) and an orange companion (mag. 6.2). My 12.5" showed the colours beautifully with wide separation over 1.5 arc minutes at 55x.

Speaking of colours, you just must see R Lep (5h, -15° — easy co-ordinates to remember); it is an intensely red star (better than the one near beta Crucis) that varies in magnitude from 5.5 to 12 over 430 days. I saw it on 29 February and estimate it to be around mag. 9. Truly it was good sight in the 12.5-inch — a deep ruby-red Mira-type variable. The star is known as Hind's Crimson Star after John Russel Hind described it in 1845 as "like a drop of blood on a black field". To find it, star hop from Orion to the first star in the central bar of the "I" (alpha Lep), then turn left, go down westward to mu Lep, then jump a little over ½ that distance again, then a tiny amount north should land you right on it. Worth showing the neighbour when it gets brighter.

To the more mundane, kappa Lep (5h 13m, -13°) is a 4.4 mag. blue-white star with quite a close companion at 7.4 mag. only 2.3 seconds apart. Due to the magnitude contrast, I found around 200x useful. It is 220 light years away and can be found by going to mu Lep via alpha (this was the way to R Lep remember) but instead of continuing straight to R Lep, hang a right back towards Orion, and quite close you will see a faint square of 4 stars—Kappa is the bottom left one.

Burnham 94 (5h 49.6m, -14°29') is deep yellow 5.5 mag. star in a field sprinkled with faint stars. It is worth a look even if you cannot split its faint close companion (nearly 9th magnitude) at 2.4"away. Use high power for this to split it.

A better deep yellow star is beta Lep (5h 28m, -21°) at 290 l.y. away. It is a lot brighter at mag 2.8. Like Burnham 94 it also has faint companion, 77.3 mag, close in (2.3").

I now know that John Herschel had a better telescope than mine when he described h 3750 ( 5h 20.4m, -21°14') as a pair that is "most beautiful". H3750 is a 4.7 magnitude star with an 8.5 mag companion at 4.1' away. To find it go to alpha, then beta Lep (the central bar of the "I"), then head of west-southwest for almost 2°. I needed around 200x power before I could split it, and I could certainly think of better "more beautiful" pairs!

Moving on to a multiple star, a small cluster (which really cannot be called a cluster) or an attractive star group, we have NGC 2017 (5h 39m, -18°). It is also known as Herschel 3780 (not to be confused with h 3750 above, duh!). At 55x my 12.5-inch shows it as a small loose 4-star arrangement with a fainter 5th star when viewed after a while. The brightest has a close 7.9 mag. companion at 0.6°— the night I observed it was not good enough to split it (well that is my story, really my mirror was not collimated enough, whatever). I enjoyed the different colours of the stars, yellow, orange, bluish and grey-white or ashy. To find it go to alpha Lep and then head east for 6 minutes. Or leave the telescope on alpha, duck inside for a quick cuppa and...voilà, there it will appear in the eyepiece when you get back! Tricky, huh?

And now to the fuzzies, M79 (5h 25m, -25°) is small but rich globular cluster 43 000 l.y. away. It can be seen as a fuzzy 8th mag. object 2.5 minutes across. It came up well between 100x to 200x power in my 12.5-inch and it resolved into stars quite well. To find it go to alpha then beta (remember the centre beam of the flatish "I", okayyy?), then continue southward, hopping the same distance again to M79. I could definitely make it out at 55x.

IC 418 (5h 27.5m, -12° 42') is a small 9.3 mag. planetary nebula about 12"across. At 90x it appeared as a bright bluish tight disk, almost starlike. At higher power it definitely became apparent as a planetary nebula. Although not by any means dazzling, I was surprised how bright it was for its magnitude. Well worth the effort to find it. Oh, yes — to find it, remember kappa Lep? You hopped from alpha then to mu Lep, then hung a right, then hopped to the small square of 4 faint stars), well point the telescope (with a low power eyepiece) ½-way between the two stars forming the top side of the square (opposite kappa, okayyy), then go inside for a cuppa (again) and come out in 7 minutes and... voilà, there it will be in the eyepiece (haven't I heard this before?), the tiniest bright blue disc all by itself.

I enjoyed looking at Lepus (the objects within it, I mean), I saw and enjoyed some objects that I would not otherwise have seen (really?). Some objects in Lepus are not the easiset to find (compared to say the Orion nebula), but anytime I started to think I was hard done on the photon front when in Lepus, I pointed my telescope towards the nearby Horse Head Nebula — now that was a challenge!

The Brilliant Star Clusters of Puppis

Jenni Kay, FRAS

The constellation of Puppis covers a large area of sky and can be easily picked out by the many bright naked eye stars involved. Also, since it sprawls across the bright Milky Way glow, it makes for an ideal area to look for some brilliant star clusters that are set against very rich, starry backgrounds. From one field to the next, the views are quite exquisite! And since Puppis is such a large constellation, it means that many consecutive nights can be spent here enjoying these splendid sights. Overall, Puppis is one of the richest areas for bright and easy finding of deep sky splendours in the southern skies.

All of the following observations were made with a 12.5" f/5 Newtonian from my semi rural home site in Lobethal, SA. The typical limiting naked-eye magnitude is 6.1 with the seeing graded at ANT II-III.

NGC 2432 : 07 40.9 -19 05

83X: Obvious enough, although it is a little lost in the rich star field. The cluster is relatively large, relatively rich, somewhat concentrated, and somewhat detached, with a size of 8.0'. There are forty stars involved all similar in brightness at around 12 mag. The main feature of this cluster is a bunching of some eighteen stars along a line through the centre of the cluster, lying north to south. 150X: More dramatic view with these sparkling gems over a smooth dark sky. In general, the cluster appears as a quaint little gem, set in a busy star field, and is certainly worth the effort to seek out.

NGC 2448 : 07 44.6 -24 40

83X: The star field is so rich it is difficult to pick out a cluster here. 150X: In the smaller 20' field of view, cutting out much of the busy surrounding star field, there is a loose star group, of some eighteen stars, all similar in brightness at around 11/12 mag. It is because the stars are the same brightness that they stand out as a group against the general, background star field. Overall, the cluster is loose, somewhat detached, 8.0' in size, with an irregular shape. There is a bright 8 mag.star near the western edge. [Some modern catalogues class this as a "non-existent" star cluster, while others find it a valid cluster.]

NGC 2453 : 07 47.6 -27 12

83X: Interesting — there is a prominent asterism of five bright stars shaping an arrowhead, where off the eastern tip there is a soft bunching of faint stars. It is this smaller (second) group which is the cluster. Overall, the cluster is small, somewhat rich, somewhat concentrated, with all of the stars involved similar in brightness at around 13 mag. 150X: More impressive view — the cluster is only 3.0' in diameter, with an overall spherical shape, and some fifteen stars involved. The view shows both the arrowhead and cluster have a combined size of 5.0', and being set in a very rich star region the lasting impression is one of being very attractive and interesting.

NGC 2455 : 07 49.0 -21 18

The field is easy to locate being a short star hop from the naked eye Theta Pup, and following a trail of bright stars as seen through the finderscope. 83X: Requires a moment to pick out the cluster in the very busy star field - relatively large, somewhat concentrated, not very rich, with all stars about 12 mag. The cluster is somewhat noticeable with its members all the same brightness in a field rich in a mix of bright and faint stars. 150X: Improved view - stands out better - there are twenty five stars involved, in a 10.0' diameter. Many of the stars lie in chains. Overall, the cluster is a neat little treasure in an attractive and rich star field.

Ha 16 : 07 50.3 -25 27

Lies about 1/2 degree southwest of Theta Pup. 83X: Very obvious, as a small knot of stars plus some stragglers. The cluster is set in a very attractive, rich star field. 150X: There are about three 12 mag. stars in the tight knot, with at least six fainter stars gathered nearby. There may be more stars involved, but they are too faint to resolve well. Overall, the charming little cluster is 2.0' in size.

NGC 2467 : 07 52.5 -26 25 OC + BN.

It is the nebula that stands out visually, with the associated star cluster appearing little more than a handful of stars shining through the neb. 83X: very obvious, bright, round, relatively large, hazy glow, with an 8 mag.star a little north of centre and a few other faint stars involved. While this is an extensive, rich and bright star field, the eye is drawn to the nebula as soon as it moves into view. 150X: Bright neb, 5.0' in size, with a very strong response to the UHC filter. Apart from the 8 mag.star involved, there are a further nine 12 mag.stars within the nebula.

NGC 2479 : 07 55.1 -17 42

83X: This is a charming little cluster, with the initial impression of being a soft spray of stars, standing out very well in the crowded, bright star field. Overall, the cluster is relatively large, rather rich, somewhat concentrated, and very well detached. The cluster has an irregular shape, with all of the stars similar in brightness at 12/13 mag. 150X: Delicate and charming — there are fifty stars sprinkled across the 20.0' field, over a smooth and dark background sky.

NGC 2482 : 07 55.2 -24 15

83X: The little starfish — the stars along the outside edge of this cluster lie in long chains shaping the outline of a starfish. It is the starfish shape that catches the eye as soon as the cluster moves into view. Overall, the cluster is relatively large, somewhat concentrated, with fifty stars involved, all similar in brightness at around 11 mag, and a size of 10.0'. 150X: Similar view. The cluster lies in an attractive, bright star field, and it is certainly worth the effort to seek out.

NGC 2483 : 07 55.7 -27 53

83X: Set in a very busy star field, the cluster takes a moment to pick out. With care, the cluster is soon noticed chiefly as a pair of long strands of stars that are twisted together near the centre. The eye picks out these strands over the very rich background of stars. Overall, there are twenty-five stars involved, with a small brightness range of 10/11 mag, and a long, irregular shape, 12.0' east to west x 5.0' north to south. 150X: improved view, the cluster more prominent confined to a smaller field cutting out some of the busy surrounding field stars.

NGC 2489 : 07 56.3 -30 04

83X: Stands out very well in the busy star field - relatively large, rich, strong concentration of bright 11 mag.stars. There are eighty stars involved in this 20.0' diameter cluster, with a strong central concentration and gradual thinning out towards the edges. 150X: Similar view. It is the whole view that is worth a mention. Apart from the cluster appearing as a gem in a busy star field, there are three bright field stars nearby displaying good colour. 13.0' south of the cluster lies a 6.3 mag.star showing a strong yellow colour, a yellow/white 4.3 dazzler lies southeast of the cluster, and a soft yellow 7.3 mag.star lies to the southwest. On the other side of this line of three stars lies the cluster Ha 20. All-in-all, a most remarkable field!

Ha 20 : 07 56.2 -30 22

19.0' south of N2489. 83X: Averted vision is drawn to a soft, granular glow from very faint stars. The cluster is small, irregularly round, with a size of 3.0'. 150X: There are a few stars momentarily resolving within the glow, about six in number and possibly 14 mag.in brightness.

NGC 2509 : 08 00.8 -19 03

83X: Very obvious, although quite soft in appearance being comprised of 12/13 mag.stars and set in a very busy, bright star field. Overall, the cluster is relatively small, strong concentration, 5.0' in size, with forty-five stars involved. 150X: Improved view, where the cluster seemed soft at 83X it now appears brighter with magnification, though still retains a delicate, overall impression. One prominent feature of this cluster shows a circlet of stars, empty within; and a trailing of stars from the circlet to the southwest.

NGC 2527 ( = NGC 2520): 08 05.3 -28 08

83X: Stands out well enough in the bright star field as a bright, loose, relatively large cluster, with a small brightness range from 10 - 12 mag. There are many rows and chains of stars in numerous geometric patterns. 150X: Improved view — the 20.0' field is strewn with mostly bright 10 mag.stars, and there are also many doubles and triplets of stars. The cluster is very attractive and certainly worthy of note. [Sir John Herschel made a duplicate observation of the same cluster, therefore we have two NGC designations but only one cluster.]

NGC 2546 : 08 12.4 -37 37

8x50mm finderscope : large, bright, hazy patch. 83X: The whole 47.0' eyepiece field is full of bright stars, and then the cluster spills over the edges. There are at least 200 stars in the field, with many in dainty pairs, charming triplets, small bunchings of stars and numerous others scattered throughout.

NGC 2567 : 08 18.5 -30 39

83X: Obvious enough, relatively large, somewhat concentrated, fairly rich, with all of the stars involved similar in brightness at 11 mag. The cluster has an overall spherical shape, 10.0' in diameter, and there are about sixty stars involved. The stars in the cluster lie in long curving chains, which are very attractive. 150X: The cluster takes magnification well, the view is much more appealing; however, there are no further details to add. NGC 2580 lies to the northeast.

NGC 2579 : 08 22.2 -36 24OC + Neb.

83X: The eye is drawn to a bright double star in the centre of a round, relatively small, bright nebula. This nebula lies at the northwestern edge of the cluster and gives a positive response to the UHC filter. In general, the cluster is a loose grouping of some eighteen 11 mag.stars, in a very irregular overall shape, 20.0' in size. 150X: There are numerous fainter background stars between the brighter and at this power it seems they too are cluster members. In this 20.0' field there are almost fifty stars including the 11 mag.stars seen at 83X, plus some fainter 12/13 mag.stars.

NGC 2580 : 08 21.4 -30 17

43.5' northeast of N2567. 83X: The cluster is almost lost in the busy star field appearing only as a slight concentration of stars in the general field. The cluster is relatively large, not very rich, somewhat concentrated, and not well detached. There are forty-five stars involved ranging from 11 - 13 mag. The cluster is 10.0' in size. 150X: Improved view — in the smaller field (20.0'), where the view is much more attractive. There are fifteen brighter 11 mag.stars mixed with the fainter over a smooth, dark background sky.

NGC 2588 : 08 23.2 -32 58

83X: Needs a few moments to spot being a small and faint cluster set in a busy star field. The cluster appears as a soft, delicate grainy, irresolved glow, where averted vision catches the flicker of some of the faint stars involved. 150X: Improved view — There are some fifty 13.5 mag.stars resolving in this well concentrated cluster, that is 2.5' in size. In the general, wider view there is a generous mix of bright and faint field stars which pretty much overpowers and conceals the faint cluster in a casual sweep of the area.

Star Asterism : 08 25.3 -32 26

42' northeast of 2588. While star hopping to N2588, I came across a very prominent asterism, which to my knowledge has no catalogue designation. The eyecatching asterism is comprised of six 10 mag. stars shaping the number "7". I found the asterism standing out so well over the very busy star field, I felt it worth a mention.

Ross Gould covered both Caleum and Columba in the April 1999 Southern Cross.