A Challenge for Large Apertures.

You will not find any of these next planetaries listed in common references - including Sky Atlas or Uranometria 2000.0. I give them as a challenge for those in the plus 30cm. class - and all have the advantage of being within a 2.2^O field! SA2-61 and SA2-64 are just visible in a 20cm. or 25cm., but the rest are uncertain. Carinae and Vela can become 'your worst astronomical nightmare' when looking for faint objects. These five all lie some 4^O north of Eta Carinae. Each has the characteristic of being bright in UHC or O-III filters. If you find the brightest, SA2-64 - you can easily attempt the others, but a warning - these may push 'Pyrex to the Limit'!

SA2-61/ He2-49/ WRAY 16-71/ PK283+2.1 (10315-5520) is the brightest of these five. The photographic magnitude is 12.7p, but I estimated the visual magnitude to be more like 13.2± 0.2. Some confusion exists in regards the nomenclature, and we sometimes delete the Sanduleuk reference, although Mayall discovered it spectroscopically in 1951. It can be found 1.1^O WNW of x Velorum (See "Surrounding Field" in this part.) SA2-61 is placed within a 18' triangle of 8th magnitude stars. Using the western star of this triangle, move 8' east, and the telescope is centred on a small trapezium of 12th magnitude stars. In the centre of the trapezium is the planetary. I saw a round colourless and featureless disk, some 4"sec.arc. across, that appeared particularly obvious when blinking the O-III filter. Catalogued diameter is 7.6"sec.arc., with the faint PNN at 17.2 mag., though some later sources state 16.9.

SA2-64 / He2-52/ WRAY 16-75/ PK285+1.1 (10385-5647) in a 30cm., I found it about ten frustrating minutes of searching before I could truly identify it. Discovered by Lubos Perek in 1960 (though some state Heintz did in 1964), it lies 1.2^O south of x Velorum. Most references state that SA2-64 is 14.0 ph., though I estimated the visual magnitude between 13.6 and 13.8. It appears as a tiny Neptunian size disk, a mere 3.0"sec.arc. across. Flicking the O-III over the field, the planetary is the one that slightly jumps at you, but it is obvious because most of the surrounding stars just disappear. I found that I had to check each of the field stars to make certain of the PN. Using a 6mm. Orthoscopic (346X in a 20cm.), the tiny disk was easily visible. Surface brightness was even, and I noted a distinct lack of colour.

SA2-65 / He2-53/ WRAY 16-76/ PK 285+1.2 (10395-5706) is the next assignment, and it is closest to the Vela-Carina border by 3'. From SA2-64, SA2-65 is 22'min.arc. to the S.S.E. Within the centre of the field is a bright 'cross'. The stars are respectfully; SW at mag. 5.9; SE 7.7; NW 8.1 and NE 8.6. The planetary lies at in intersection of this cross. I did not see this object, though I could identify the field easily. In the 30cm. the O-III filter turned up nothing. At photographic magnitude is a tough 15.0p, while the planetary is only about 5.0"sec.arc. Observers using the 40cm. at Bowen Mountain could have better luck.

SA2-66 / WRAY 16-77/ PK 285+2.1 (10413-5609) is even fainter, and is set at magnitude 15.4p. I could not see this through lack of aperture. The field contains two 6.7 and 8.7 mag. stars, separated by 3'min.arc. Using the 8.3 magnitude star, the planetary lays 4' SW, and below the two 12th mag. field stars. The Strasbourg/ ESO catalogue states the diameter is uncertain, but the STScI image shows that it is about 8" to 10"sec.arc.

I would appreciate any amateur observations of this planetary or SA2-65.

SA2-68/ He2-55/ WRAY 16-79/ PK286+2.1 (10487-5603) is likely an impossible target for amateur observers. Using x Velorum, it lies 1.4^O to the S.E.E. The field contains a stretched trapezium of stars, with the brightest being mag. 8.3 to the NW. Two others, to the NE and NW, are 9th mag. stars that appear as wide triples. The planetary is west of the solitary southeastern star by 2.5'min.arc. The American Karl G.Heintz in 1964 discovered it. For the amateur it is faint at photographic magnitude 15.0, while the visual magnitude is c.14th. The disk is some 18.0"sec.arc., with a very low surface brightness. SA2-68 has a PNN magnitude reported to be 17.4. This is the hardest object in this Sanduleuk quintet.

[Note: I have only included SA2-68 for those currently in remission from the incurable disease, commonly known as Bi Radii Dobsonia Reflectus Extremius or simply aperture fever! Treatment for this disease is very expensive - so members remember - please humour them!]

Little is known about these five objects, but all belong to the section of the Vela spiral arm of the Milky Way. All are likely quite distant. I suggest that if you do search for them - wait for a night of good seeing. One problem with very small planetaries, is that they appear to merge with the other stars in the field. Although an O-III helps you find them, if the resolution is not there, it will appear as a normal star. Perhaps Andrew Murrell and his beloved Hector, or one of our beloved and foolhardy astrophotographers, may like to take up the challenge and try to capture these objects?

Surrounding Field of 'The Five Planetaries'.

x Velorum/ 95 (AB) and HJ 4341 (BC) (10393-5536) is third in my Top 5 of favourite double/ multiple stars. I have named it 'Albireo Australis'. (Alpha Centauri is first, Gamma Velorum is second, Beta Cygni is fourth, Acrux is fifth.) In 1826, James Dunlop discovered the wide and bright AB components (Mag. 4.4/ 6.6) at Parramatta Observatory. Separation is 51.9"sec.arc. at position angle 105^O. (See Figure 4.) Little has change in the relative positions of the two stars since the Dunlop's first measures. The ASNSW Double Star Section during the 'Double Star Colour Estimates Programme' (DSCE) in 1979-81, saw the star colours as orange-yellow and pale blue. The thirty-six members of the ASNSW and other contributing Societies assessed this. H.C.Russell on the 21st March 1873, described the colour as straw yellow and greenish blue. He comments also that "Glimpse several minute points near this." The colour difference is magnificent, significantly enhanced by an optical illusion - reflect by star's spectral classes; G2-3 Ib and B8 V. Difference in magnitude ( m) is 1.2, though the twelve observers in this part of the programme overall estimated the difference is closer to 1.8. Closer inspection reveals that the blue component is again double, and Sir John Herschel discovered this pair, HJ4341, some eight years later than Dunlop. Burnham's incorrectly names' it 95b, and saying the primary AB is HJ 4341. Russell also incorrectly assumes that the HJ 4341 was the AB system, though Herschel's observation implicitly refers to the BC system. Such a discrepancy is difficult to explain satisfactorily, as the AB pair is too obvious. The third 11th magnitude yellowish star is found opposite to the 'A' component, at PA 176^O. We measure separation of 20.2"sec.arc. as a third the distance between A and B. This can glimpse this in a 7.5cm., though a 10.5cm. will prove better in seeing the component from the bright glare of the 'B' component.

All three stars have the same common proper motion, so it is still possible that this might be a physical system. However, if it is, the periods are likely to be very long time.

The field is dense with stars, and contains another 8.2 magnitude star some 6'min.arc. at PA 120^O. This colourful triple is one of the most attractive objects in the south - even for the smallest of telescopes.

J Velorum/ Rmk 13 (10209-5603) is a spectacular triple which lies in a dense stellar field, some 2.6^O WSW from x Velorum (or 2.5^O WNW from SA2-64). Unlike most system Rumker discovered the AC pair first in 1835, and the AB pair a year later. I suspect he may have missed the brighter AB pair, because of bad seeing and not be carelessness. The main pair is magnitude 4.5 and 8.4 and separated by 7.2"sec.arc. at position angle 102^O. I see the colours as blue-white, and could discern no difference. AOST2 describes them as white, and stating "...this is a beautiful object." Spectral types for the two Giant stars are B4 and B9.5. The pair is visible using medium to high power in a 10.5cm., and medium power in a 20cm. Difficulty in the separation for smaller apertures is more from the m=3.9, than the quality of the telescope. Component 'A' has been found to show a variable spectrum, and a suggestion says that this maybe either spectroscopic binary, or that this star has some peculiarities. Some 37"sec.arc. (PA=102^O) to the south of the main pair is a 9.8 magnitude star. (SAO 277958) This wider star is easy in a 7.5cm., and I see the colour as yellowish-white. Little has changed in the positions, so it is uncertain if all the stars are physically associated.

AR Vel (10400-5944) is a faint detached Algol (EA) eclipsing binary system in the same field as SA2-64. It can be found between the planetary and a 9th magnitude to the ENE. (Using a 20cm. at 76X) Over a period of 3.21275 days (3d 05h 06.4m), the stars vary between 12.0 and 12.6p. The duration of the darkest eclipse is some 9 hours 15.1 mins. (0.3856 days). Observers have made few observations of this system since 12th February, 1925 (JD=2424193.324.) Observers may like to check the time of the primary eclipse, as the small variations in period of 77 years may have significantly changed the time of mid-eclipse.

ZZ Vel (10379-5557) is another detached main sequence EA-type eclipsing binary. It can be found some 30' NNE of SA-66, and 20'min.arc. SSE of x Velorum. Magnitudes vary between 9.93-10.39 in a period of 2.87615 days. The primary is a blue A0V. Duration of the primary eclipse is 11h 02.6m (0.460184 days), last adjusted made on 8th October 1923. (JD=2423700.42). Although, the magnitude difference is a mere 0.45, observers may like to check ZZ Vel over an observing night if they can detect any variations with any of the other stars in the field.

Postscript 1 : Neat Planetary Web Sites - Do Your Socks!

I have come across several web sites that have brilliant images of some planetaries. The first is one of the most beautiful series of planetary nebulae images I have ever seen, but the other sites are just as interesting. These sites include;

http://www.blackskies.org     Planetary Nebulae Observer's Home Page - You Are Here!
http://seds.lpl.arizona.edu/billa/bb/inline.html
http://www.noao.edu/jacoby/pn_gallery.html
http://www.noao.edu/jacoby/more.html
http://www.noao.edu/wiyn/

Postscript 2 : Finder Charts for Planetaries