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Southern Cross - April 1998

• Constellation of the Month - Leo Minor and Ursa Major
• Notable Australian Astronomers - Walter Gale
• RCW 57: a remarkable nebulae complex in Carina

Constellation of the Month - Leo Minor and Ursa Major

Steve Crouch

Ursa Major is probably one of the best known constellations of all and one of the easiest to pick out if you are in the northern hemisphere. Unfortunately, we see only its extreme southern regions at these latitudes but there are still a few good things to look at. For the benefit of anyone travelling north in the near future, I will also mention some of the other highlights of Ursa Major that I saw on a visit to Hawaii several years ago.

Leo Minor is a far less distinguished constellation formed by Hevelius in 1660. It is situated between Leo and Ursa Major. Given the distance from the galactic plane of both constellations, globulars and open clusters are absent but Ursa Major does have one famous planetary nebula (M97 - The Owl nebula) which is unfortunately invisible from Canberra latitudes.

The observations in this article were done with my newly acquired C14 mostly using a 35mm Panoptic eyepiece giving a magnification of about 111x. It should also be noted that, observing from Theodore, Ursa Major and Leo Minor are deeply embedded in the Canberra sky glow and someone observing from the north of Canberra would probably do a lot better.

Double Stars

I only managed to observe a few of these so I will mostly rely on the entries in Hartung.

Struve 1374 (RA 09h 41.4, Dec. +38d 57m) is said to be a test pair for 7.5cm. The component magnitudes are 7.3 and 8.6 and the separation is 3.0".

Xi UMa (11 18.2, +31 32) is an interesting system with almost equal components of magnitudes 4.3 and 4.8 where the separation varies from 0".9 to 3.1" over a period of 60 years. As it was at its closest in 1993 it may now be reasonably difficult for small telescopes. Given the turbulence of the atmosphere, I could not say that I split it but I did see some elongation.

Nu UMa (11 18.5, +33 06) is a widely separated pair at 7.3" with 3.5 and 9.9 components.

57 UMa (11 29.1, +39.20) is stated to be a fine pair with 5.3 and 8.3 components separated by 5.6". I split it easily at low power with the C14.

Galaxies

A sampling from both constellations follows. Given that these are mostly in the magnitude 10-11 range, 20 cm from a dark sky should be sufficient.

NGC 3245 (10 27.3, +28 30) was fairly bright at magnitude 10.8. I could not see any structure, however. NGC 3254 (10 29.3, + 29 30) was, by contrast, very hard to see through the Canberra glow. I had no trouble with NGC 3344 (10 43.5, +24 55) as it is quite large and bright.

NGC 3486 (11 00.4, +28 58) is also quite large and bright.

NGC 4031 (12 00.5, +31 57) is an averted imagination job. The photographic magnitude is stated to be 14.

NGC 4062 (12 04.1, +31, 54) is much easier but still fairly faint. The C14 shows it as an elongated blur.

From Hawaii, I saw M 81, M 82, M 97 and M 101 (all in Ursa Major) with a 17 1/2" Dobsonian. M 81 should be familiar to CAS members as it is the galaxy used on the T-shirt emblem. It was bright, but not particularly interesting in terms of structure. The famous starburst galaxy, M 82, reminded me of a smaller version of our own NGC 55 in Sculptor. The planetary nebula, M 97, although having a fairly low surface brightness, clearly shows its owl face shape in this aperture. My favourite object of this group of four was the face-on spiral M 101. Through the 17 1/2" it simply overflowed with detail. It is a low surface brightness object, however, and is not as impressive in smaller telescopes.

Notable Australian Astronomers

Ross Gould

Walter Gale is one of several notable amateur astronomers who appeared at the end of the 19th century when John Tebbutt was nearing retirement. Gale was born in Sydney, and early developed an interest in astronomy - Harley Wood, who knew Gale in his later years, records that “he always said that he did not remember the time when he did not know the constellations”. His father encouraged his interest in astronomy, and this was reinforced by the Great Comet of 1882. His observing began with a small refractor, and in 1886 at age 19 he built himself a 7-inch reflector.

Gale was known both in scientific circles and among the public for his work in astronomy, rather than for his professional life, which was mostly with the Savings Bank of NSW, later the Government Savings Bank of NSW, in which he rose to become manager of the Head Office. He retired in 1925. Gale was a keen populariser of astronomy as well as producing many papers based on his observing. He was also a member of the Board of Visitors to Sydney Observatory for 28 years, being its chairman at the time of his death.

As a planetary observer he appears to have been the first to notice the Martian markings known as “oases”, and in 1892 he discovered several previously unobserved “canals”. He also extensively observed Jupiter and Saturn, and many of his planetary observations were published in the Journal and Memoirs of the BAA. His planetary work, like his comet hunting, continued for decades. Comet hunting was a life-long commitment. Of his seven comet discoveries, three were named for him (1894b, 1912a, and 1927f).

In 1894 he discovered a number of double stars and a ring nebula (IC 5150) with his 8.5-inch reflector. Among his other published observations are timings of crater immersions into the Earth’s shadow during lunar eclipses (1892 and 1906); the 1894 Transit of Mercury; various bright meteors; lunar occultations of Spica (during the day) and Antares, and the occultation of a star by Mars; and the naked-eye visibility of Venus by day.

Harley Wood remarks that “During his lifetime he owned more telescopes than pass through the hands of most astronomers, either professional or amateur...”. A number of telescopes he built himself, making the mirrors. He owned an 8.5-inch reflector by 1892, later 10-inch and 18-inch reflectors. Wood mentions two 18-inch reflectors - one of these had a mirror by the famous English maker George Calver; in the 1970s this mirror was remounted in a telescope at the University of Wollongong. Gale also owned a 6-inch refractor, and for a time - after John Tebbutt’s death - the 8-inch Grubb refractor that later went to Frank Bateson in New Zealand and is now back at Windsor. Other telescopes are mentioned in his published papers.

Walter Gale became an FRAS in 1893, at nearly the same age as John Tebbutt - a point noticed by Tebbutt, who was reluctant to sponsor Gale’s election at that time. Also like Tebbutt, he was awarded the Jackson-Gwilt medal of the Royal Astronomical Society, in his case in 1935 “for his discoveries of comets and his work for astronomy in New South Wales”.

In 1893 Gale travelled overseas, observing the eclipse of the Sun in Chile with the Lick Observatory expedition, and visiting observatories in America. On his return, he became very actively involved in the founding of the NSW Branch of the British Astronomical Association, an organisation notable in NSW for its outstanding membership and commitment to observing particularly from its founding in the 1890’s until the First World War. Gale was the Branch’s first Secretary, and was President for 20 years. He was a member for over fifty years.

Gale led the NSW group to observe the solar eclipse of 1922 from Stanthorpe in Queensland. He had also observed the 1905 partial solar eclipse, and been prevented by cloud from observing the total solar eclipse of 1910. Cloud also prevented his “usual sweep of the sky” on 1 June 1945; later that night he died of a heart attack.

RCW 57: A Nebula in Carina

Jenni Kay, FRAS

In this article I have included descriptive notes on the complex as seen through both an 8-inch and 12.5-inch telescopes. Further to this, I have also inserted the historical 1834-38 observation notes made by the discoverer of the NGC objects, Sir John Herschel. Herschel used a 20-foot reflector of 18 inches aperture speculum mirror.

The following observations were made with an 8" f/10 SCT, and a 12.5" f/5 Newtonian, from my semi-rural home site in Lobethal, SA. Typically the limiting naked-eye magnitude is 6.1, with the seeing rated at Antoniadi II-III.

The seven NGC objects of RCW 57 are: NGC3576, NGC 3579, NGC 3581, NGC 3582, NGC 3584, NGC 3586, and NGC 3603.

The general view through the 8" f/10 SCT.

In a low powered field, (66X, 46' FOV) NGC 3581 and NGC 3582 appear as a bright, obvious, single, large hazy mass. This hazy mass has an overall fan shape, widest in the north, with a size 5' north to south, by 3' east to west. In the southern region of this haze lies a noticeably brighter knot, which is in fact NGC 3581 itself. It is difficult to realise visually that the two nebulae, NGC 3581/ 82, are here, since one joins and blends into the other. North, and well detached from the main, fan-shaped haze, there are two much softer hazy glows. These nebulae are NGC 3579 in the west, and NGC 3584 in the east.

Only with a careful study of the field can I detect the very subtle glow from NGC 3576 southwest of the main fan-shaped haze. NGC 3586, which lies southeast of the principal haze mass, is too faint for me to detect. East, and well detached from the main nebulae complex, lies the very obvious NGC 3603. This is easily noticed as a very bright star wrapped in bright nebulosity. In the rest of the field there is an extensively rich mix of bright and faint field stars against the background milky way glow. The whole view is impressive and interesting! See figure 1 which is an AAT image annotated to show the locations of the six NGC objects. Following is a closer study of each NGC nebula.

NGC 3576 : 11 11 32.7 -61 21 48
N3576 = JH 3324
"F; oval; The first of a group of 6."

8" f/10 SCT. 110X; 28' FOV.
I can barely notice the small, round, very soft glow from this nebula, but averted vision detects the nebula with full confidence. The round, subtle glow may be 1-1.5' in size. Immediately west of the nebula is a mag 12 star, and in order to locate the nebula again I find it helpful to search for this star first. The star lies about 5' southwest of the main, fan-shaped haze.

12.5" f/5 Newt.
105/151X: slightly elongated, tuft of relatively faint nebulosity, 2.0' x 0.5' in size, easy enough to spot with averted vision. Three 12/13 mag stars involved lying in a line almost east to west. Positive response to the UHC filter showing the nebula very strongly.

NGC 3579 : 11 11 58 -61 14 41
N3578 = JH 3325 "F; oval. The 2nd of 6..."
"R, sbM, by diagram."

8" f/10 SCT. 2' North and well detached from the main, fan-shaped haze is the dim glow from this nebula. The haze is a round patch, and may be 1-1.5' in size. A mag 12 star lies at the southeastern edge of this nebula.

12.5" f/5 Newt. 105/151X: relatively bright, irregularly round, 2.5' in size, relatively large fragment of nebulosity northwest of main hazy mass. UHC: very strong, bright, smooth, even glow throughout. 12 mag field star at southeastern edge.

NGC3581 : 11 12 00.0 -61 18 18
N3581 = JH3326 "Fanshaped, adhering to a star. The 3rd of 6. Place of direct obs."
"A * 12m, with a fan neb attached."

8" f/10 SCT.
This nebula lies in the southern region of the main, fan-shaped haze. It appears as an obvious, bright, elongated knot, northeast to southwest, with much softer extensions fanning to the north. There is a mag 12 star at the tip of the nebulous knot. 1.5' east of the nebula lies a very bright, mag 9 star (SAO251313).

12.5" f/5 Newt.
105X: Very obvious, very bright, small knot in the southwestern region of the main haze mass. UHC: Very strong response. 151X: Fan shaped, 2.5' in size.

NGC 3582 : 11 12 08.1 -61 16 30
N3582 = JH 3327
"A * 11m in centre of a round neb. (The 4th of 6.)..."
"R; has a * in middle..."

8" f/10 SCT.
In the northern region of the main, fan-shaped haze, lies a mag 10 star, and around this star, the nebulosity appears a little brighter again. This nebula is irregularly round and large. Since neither NGC 3581 nor NGC 3582 appear as two separate nebulae, I am only able to estimate a size of 5' x 3' for the whole hazy mass.

12.5" f/5 Newt.
105X: Hardly perceptible as a separate identity to NGC 3581, however it does seem to be slightly fainter than 3581. Overall, it is bright, irregularly round, large, 3' in size, with at least three stars involved. UHC: strong. 151X: six stars resolved, one 11 mag star near the centre, the rest ~ 12 mag.

NGC 3584 : 11 12 19.2 -61 13 12
N3584 = JH3329
"F; L; oval; bM; The 5th of a group of 6."
"L, bM, E in merid.."

8" f/10 SCT.
3' North and well detached from the main, fan-shaped haze, and east of NGC 3579, lies this long, streaky nebula. The UHC filter enhances the view of this haze. There is a mag 11 star at the southern tip, and a mag 12 star at the northern end. The haze is 5' long, north to south.

12.5" f/5 Newt.
105/151X: Bright, broad, long curving wisp of nebulosity, 5' north to south. Wider at southern end, 1' in width, and tapers to a fine tip in the north. UHC: strong, smooth glow. Two stars at the northern edge, one star at the southern.

NGC 3586 : 11 12 29.2 -61 20 54
N3586 = JH3330
"S, oval,...the last of a group of 6."
"eF; oval..."

8" f/10 SCT.
4' Southeast of the main body of nebulous haze. The glow from this nebula is too weak for me to detect.

12.5" f/5 Newt.
105/X: Relatively faint, long wisp, which averted vision detects and holds easily enough. UHC : good response.

151X: Slim streak, extended north to south with a size of 2.5' x 0.7'.

NGC 3603 : 11 15 07.0 -61 15 33
N3603 = JH 3334
"A red star 10 m, the centre of an excessively condensed group of stars 15....18m, with a nebulosity extending over 2' diameter"
"Viewed the neb of sweep 432, No.21, [preceding observation] which is a very remarkable object. The centre, when examined with powers 240 and 320, decidedly not a star, and the nebula about it all resolved. Perhaps it is a globular cluster vsvvmbM."

8" f/10 SCT.
About 23' east of the principal nebula complex, lies this obvious compact star cluster in nebulosity. At low power, 66X, it appears bright, nearly stellar in size, equal in brightness to a mag 9 field star, and set in a bright hazy patch. At 110X, the near-stellar object is more of a very bright, very small knot, with some nearby mag 10 stars, all encompassed in nebulosity. The brighter knot lies at the northeastern edge of the nebulosity. Overall, the neb is fan-shaped, about 3.0' in size, with the brighter knot being 0.3' in size.

12.5" f/5 Newt.
105/151X: Eyecatching -- bright, very small knot plus stars grouping around it, all wrapped in bright nebulosity. Seven stars involved, ranging from 9 - 12 mag. The nebula has an irregularly round shape, 3' in size, with a very strong response to the UHC. This object is so obvious it would not be overlooked in a general sweep through this very rich star region.