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Southern Cross - October 2002

• Indus by Albert Brakel
• The Bennett Catalogue : Ben 125 - Ben 3 by Jenni Kay

Indus

Albert Brakel

Indus is one of Bayer's new constellations introduced in 1603, and named in honor of the North American Indian, but placed incongruously in the deep southern sky. It has an irregular shape with no readily recognizable star pattern. To find its northern half, where most of the easiest objects are, look between Alpha Pavonis and the promin-ent pattern of Grus. The rest of the constellation stretches south between Tucana and Pavo as far as Octans.

Frankly, Indus does not rank high on any sky tourist's priority list, and contains only some not-very-bright galaxies, and double stars.

Let's start with Theta Indi (RA 21h 19.9m, Dec. -53° 27'), right in the middle of the northern half of Indus, and about midway between Alpha Gruis and Alpha Pavonis. This is the best double star in the constellation, a very unequal pair consisting of a mag. 4.5 A5 primary and a m.7.1 G0 secondary, an easy 6.6" apart and lined up E-W. They were easily split with 77x. The spectral types suggest they should be white and yellow respectively, but Hartung saw them as pale yellow and reddish. To my eyes they looked very pale yellow and deeper yellow.

Halfway between Theta and Delta Ind, a fine edge-on spiral, NGC 7090 (21h 36.5m, -54° 33') glows at mag. 10.7. Unfortunately it was only barely visible with averted vision in the suburban sky of Downer with a 20 cm aperture, and no structure could be seen in it. It is oriented NW-SE. Though not an easy sighting, it was a confident one. There are several scattered stars in the same field, including a very wide equal optical pair lying to the east.

Two degrees SSE of Delta lies Epsilon Indi (22h 03.4m, -56° 47'), a m.4.7 deep golden yellow star about 11.5 light years away that has been a target of SETI searches. It has the unusually large annual proper motion of 4.7", which will carry it near the region of the south celestial pole in about 50,000 years.

About a degree SE of Epsilon, NGC 7205 (22h 08.5m, -57° 25') is a m.11.1 galaxy on the border with Tucana. The barest of feeble diffuse glows from Downer, it faded towards the edges but had no noticeable core region. It lies between two stars, a brighter one on the western side and a fainter one to the east.

Slide not quite 4 degrees north of Delta Indi, and halfway to Alpha Gruis, and you find IC 5152 (22h 02.9m, -51° 17'), a dwarf irregular galaxy about 5 million l.y. distant, in the northeastern corner of the constellation. Positioned in front of its northwestern end is a glary mag. 7.5 star that hinders observation more than somewhat. Nevertheless I could dimly see the ESE-elongated shape. It resides between the Local Group and the Sculptor Group of galaxies, but belonging to neither, making it one of the most isolated dwarf galaxies known. Owners of really big mirrors could try resolving stars in this galaxy in good conditions.

Turning now to five degrees due north of Theta Ind, NGC 7049 (21h 19.0 m, -48° 34') is the brightest member of a cluster of galaxies in that region. It lies about 15' east of a bright (m.6.5) yellow star. It appeared as a small, round hazy spot, visible with direct vision in the suburban sky, and brighter than any of the galaxies so far considered.

Nearby, I tried two other members of the galaxy cluster: NGC 7041 (21h 16.5m, -48° 22') and NGC 7029 (21h 12m, -49° 13'), but failed to see them, even after I cranked up the power to 154x to increase the contrast. If you have a darker sky though, they would be likely candidates.

NGC 7192 (22h 06.8m, -64° 19'), in southern Indus close to the Tucana border 7½° south of Epsilon (and 4° SSW of Alpha Tuc), seemed another possibility, but it too was elusive.

I decided to continue with some unidentified binaries marked on HB Astroatlas chart C77. One located 2½° WSW of Epsilon Ind (21h 43.0, -57° 19.5') turned out to be such a very wide pair that it just had to be an optical double, confirmed by Sky Catalogue 2000.0 which gives the respective distances as 49 and 61 parsecs (160 and 199 l.y.). The stars are pale yellow and mags. 6.5 and 6.9. With a deeper yellow m.7.3 star only a bit further to the southwest, the three make a fine sight.

Next I went for a binary half a degree south of Nu Indi in the far south, HD211931 (22h 23.7m, -72° 48'). This was revealed as a wide pair easily resolved with 50x, both pale yellow, and aligned E-W. The primary (m.7.8) lies on the east side, and is only slightly brighter than its companion.

Another unlabelled double star sits about ¾° east of Mu Indi, and was just resolved with 77x (it was elongate and on the verge of resolution with 50x). It is catalogued as HD201247 (21h 10.4m, -54° 34'). The components are yellowish and almost of equal magnitude (about m.7), with the secondary to the southeast of the primary.

Finally, I can't resist throwing in something for those who want a really serious challenge. This one is not for the faint-hearted or the small-'scoped, and needs a demanding mix of a large aperture, dark sky, good seeing, observational skills honed by experience, and lots of patience. Abell 3716 (20h 51.5m, -52° 42', about a degree south of m.5 Iota Ind) is a cluster of more than 60 galaxies lying nearly 1 billion light years away. If you see any at all, you will see the brightest one, a mere 1' across and mag. 13.6. With care, you may pick up more of the barely non-stellar objects, up to a dozen or so in a square degree. Good luck!!

The Bennett Catalogue : Ben 125 - Ben 3

Jenni Kay FRAS

This month I return to working on observations from the Bennett Catalogue project. Here in the Adelaide Hills we've had rather poor skies the last couple of months, and so, it's not only good to get back to the telescope now, but it's even more enjoyable to start with a list of bright and easy targets. As an added bonus, I noticed there were a few other galaxies lying in the same fields as a couple of the Bennett objects. I've included them in the list below, along with a couple of galaxies that were too faint for me to detect. If anyone out there is able to make a positive observation of those “too faint" galaxies I would like to hear from you, and learn what telescope and sky condition revealed them.

The following observations were made from my semi-rural home site at Lobethal, SA, and the telescope used is noted beside each object record. Typically, the skies here have a limiting naked eye magnitude of 6.1, with the seeing rated at ANT II-III.

Ben 125 ­- Aqr

= NGC 6981 (M72) : 20 53.5 -12 32 (GC)

12.6" f/5 Newt. 8 x 50mm finderscope: star-like in appearance. 105X: Impressive - bright, large, round hazy glow, almost granular from the stars on the verge of resolving. 150X: More splendid - bright, round, 4.0' in size, with a mostly smooth to granular hazy glow. There are six 13 mag stars resolving towards the central region, and the cluster gradually brightens towards the centre. In the general, wider field, there are two bright 10 mag field stars 5.0' to the east, and the rest of the field is lightly sprinkled with 11 mag and fainter stars.

Ben 126 - Aqr

= NGC 7009: 21 04.2 -11 22 Saturn Nebula (PN)

12.5" f/5 Newt. 105X: Very obvious - very bright, intense, with a strong nearly sky-blue colour. Relatively small, a little oval in shape, with a bright even glow from edge to edge. 150X: Similar view - very bright throughout, 40" in size, with a round - oval shape.

Ben 127 - Aqr

= NGC 7089 (M2) : 21 33.5 -00 49 (GC)

8" f/10 SCT. 6x30 finder: bright, small, round, hazy spot. There are some bright field stars nearby, but the tiny cluster spot is obvious as non-stellar. 66X: very bright, large, round hazy glow with softer extensions from unresolved outliers. 140X: Remarkable - very bright, large, compact and granular, with a much extended, softer halo from outliers. Overall, the cluster is 6.0' in size, with the brighter, central region being 1.5' in size. In the wider, general view, there is a light scatter of 10/11 mag field stars, with the bright cluster dominating the field.

Ben 128 - Cap

= NGC 7099 (M30) : 21 40.4 -23 11 (GC)

12.5" f/5 Newt. 105X: bright and impressive - with a very bright, compressed central core region within a much extended soft outer halo. This outer halo is the glow from very faint, far reaching outliers. Furthermore, the halo shows two, prominent strands of stars in straight rows from the core with one trailing to the north, the other to the northwest. There are three 13 mag stars to each row. 150X: Magnificent - the very bright core is mostly round with a size of 30", and the halo gradually fades out to the edges to an overall size of 4.0'. There are about twenty stars resolved in the halo at this power, and these are spread evenly across the cluster.

Ben 129 - Aqr

= NGC 7293 : 22 29.6 -20 48 Helix Nebula (PN)

12.5" f/5 Newt. 8 x 50mm finderscope - obvious, faint, large, round, hazy stain. 105X: WOW!!! Bright, large, round, annular. There are five stars within the dark, central region. There is a very positive response to the UHC filter. 150X: 18.0' in size, seems stronger along the northern side. The central star, 13 mag, is clearly seen lying a little off centre to the north.

Ben 129a - Gru

= NGC 7410 : 22 55.0 -39 39 (GX) GRU

12.5" f/5 Newt. 105X: Very obvious - very bright, long and broad, gradually brightening to an almost stellar nucleus. The surface glows seems uneven, hinting at some structure by a mottling effect. 150X: Improved view - bright, 3.0' x 40" in size, major axis lies NE - SW, with a brighter round core region, 30" in size, and a stellar nucleus. The galaxy has a high surface brightness, with the mottling effect still apparent. Overall, the general, wider view is most charming! There is a light sprinkle of bright 9/10 mag field stars around the prominent galaxy, and a smooth, dark, background sky.

NGC 7404 lies 22.0' NE, and is worth a mention. At 105X: it is obvious enough, relatively bright, small, round to a little elongated, hazy smudge, with a stellar nucleus. 150X: Improved view - relatively bright, small, 35" x 15" in size, major axis lies almost N-S, and brightens to a stellar nucleus. The galaxy lies among a small group of 5-6 bright stars, the group is well detached, 10.0' in size, with the galaxy easily picked out as a small fuzzy.

Ben 129b - Gru

= IC 1459 : 22 57.2 -36 28 (GX)

12.5" f/5 Newt. First up, the field is easy to locate being a short, 6 degree star-hop south of Fomalhaut, and there is a good trail of bright stars to follow to it. 105X: Very obvious - relatively bright, relatively large, round - oval in shape, with a very bright, small, round core. 150X: Improved view - bright, 2.0' x 1.0' in size, major axis lies NE - SW, with a very bright core 25" in size and a high surface brightness. In the wider general field lie a few other galaxies, and these are listed below.

IC 6264 lies 6.5' SW. 150X: obvious - relatively bright, long, slim, hazy wisp, 2.0' x 25", major axis lies almost E-W, with a smooth and even, high surface brightness, gradually brightening towards the centre.

IC 5269B lies 14.5' NE. 150X: needs averted vision - extremely faint, relatively long and broad, 1.5' x 30" in size, axis lies almost E-W, with a low surface brightness.

IC 5269 lies 27.5' NNE. 150X: very obvious - relatively bright, relatively small, elongated NE - SW, 1.0' x 25" in size, slightly brightening to an almost stellar nucleus. High surface brightness.

NGC 7418A lies 19.5' SSW. Too faint.

IC 5269A lies 16' NWN. Too faint.

Ben 130 - Scl

= NGC 7793 : 23 57.8 -32 35 (GX)

12.5" f/5 Newt. 105X: Wow! - Bright, very large, oval in shape, hazy glow, gradually brightening towards the centre, with a very small, round core, and suspected stellar nucleus. Overall, the galaxy appears very soft and smooth. 150X: Improved view - bright, 8.0' x 7.0' in size, major axis lies ESE - WNW, with a brighter core 10" in size, and a stellar nucleus.

Ben 1 - Scl

= NGC 55 : 00 14.9 -39 11 (GX)

12.5" f/5 Newt. 8x50mm Finderscope: relatively faint, long, thin, hazy wisp. 50X: Very impressive - bright, long and broad, brighter on the western half of the galaxy glow. This brighter end seems mottled, with three stars superimposed, or three almost stellar-sized hazy knots. The eastern and fainter half also appears mottled. The whole length of the galaxy must be about 25.0'. 105/150X: The overall size is 25.0' x 2.0', stretching across the field nearly NW-SE. There is one bright, very small, round knot near the centre. There are also two stars or two very small knots in the west. The brighter half seems to bulge, giving the galaxy an uneven shape.

Ben 2 -Tuc

= NGC 104 (47 TUC) : 00 24.1 -72 05 (GC)

8" f/10 SCT. Known as one of the finest objects in the southern sky, this globular cluster is an easy target for the smallest of optical instruments. In at least 7x50mm binoculars, the globular appears as a brilliant haze surrounded by a much softer and extended glow. At 66X, through the 8" SCT, the stars sprawl across the field in a magnificent display. There is a brilliant, grainy core, 2.0' in size; enveloped in a large mass of stars and haze, 7.0' in size; and numerous outliers stretching to 28.0' in diameter. At 140X: there are at least 150 stars resolved well and these are scattered throughout. The whole view reminds me of a splendid firecracker bursting into trails and count-less points. All magnifications offer appealing views but the higher the magnification the stronger the visual impact.

Ben 3 - Scl

= NGC 247 : 00 47.1 -20 46 (GX)

12.5" f/5 Newt. Obvious - relatively bright, very long and broad, with a large, bright, central bulge, and a 10 mag field star at the southern tip. There are a few field stars superimposed in the southern region of the halo. Overall, the galaxy has a smooth and even surface brightness. 150X: Improved - relatively bright, 20.0' long by 5.0' wide at the central bulge, and then tapers towards the tips. The major axis lies N-S.