This installment covers two planetaries in southern Vela, placed to the east of the asterism of the False Cross.

NGC 2899 / He2-30/ WRAY 16-47/ My 48/ Gum 27/ RCW 43/ PK277-3.1 (09270-5606) (Vela) was first discovered by Sir John Herschel in 1835. NGC2899 is found in a moderately bright star field, found some 8'min.arc. west of the 7.6 magnitude star SAO 236965. The blue Kappa ( or ) Velorum (Markab or Markeb) is the nearest bright star (Mag. 2.6), which is the most easterly star in the False Cross. Culminating at midnight on the 26th March each year, taking the mid point between Kappa Velorum and the orange N Velorum easily finds the planetary. (2.7^O SE from Kappa Vel). Using a 20cm., it took me less than thirty seconds to find the object. NGC 2899 does not appear in Sky Atlas 2000.0, but does appear listed in the Catalogue. However, they correctly identify it in Uranometria 2000.0.

At visual magnitude 11.8, a 15cm will show the planetary plainly, with a 25cm. or greater starting to show some structural details. They state a photographic magnitude in some sources to be between 9.7 and 12.2, with the later perhaps being closer to the truth. Unlike some planetaries, this object improves with magnification.

The structure of this planetary is unusual, and though they give no classification of structure, the photographic images show that it might be anomalous - a possible Vorontsov-Velyaminov Type VI (6). However, visually it appears closer to a Type IV! My first observation was made during particularly bad seeing, and the visibility of the outer edges or of the mottling within the nebulosity was impossible. My next session showed a vast improvement, as the night was so good, that at 420X I could still see the faint hole in the centre. An O-III filter made the hole appear prominent, and in all, vastly improved the structures within the nebulosity. I was surprised to be able to see this 'hole', as only a few observers have claimed to see it using apertures above 30cm.

The edges to me looked unusually uneven, especially to the east and north, and in some ways even reminded me of NGC 5189 in Musca or even NGC 5844 in Triangulum Australe. Throughout the literature, it seems that it is overall structural quite different. AOST2 states;

"... It is an irregularly oval luminous planetary nebula about 1.5' across, of rather uneven light and showing its emission nature by its single prism image."

According to the AAO website, David Malin took the colour image using three separate plates at 385nm., 495nm. and 630nm. Each exposure of NGC 2899 was taken for 30 minutes, and combined into a single image. Listed as A beautiful colour image of AAO Slide #109, also appears in AOST2 as Plate 61.

I thought that the nebulosity appeared yellowish - and this is quite different other planetaries discussed in this series. There seems quite a difference between the visual and photographic images. Visually it appears to me as a mottled annular disk, which is brightest at PA 40^O. Averted vision help discerns the appearance of the mottling, showing that the surface is uneven. Photographs show a more square or 'chair-like' structure, that some claim to think is more like an 'abstract' butterfly.

In size, the nebula covers about 90"sec.arc., though some sources say 110"sec.arc. Deep sky photographs, show the edges extend to a maximum of c.120"sec.arc.
Doubt was expressed of the planetary nature of this object in 1968. To quote Hartung in AOST2;

" This object is not listed either as a planetary or a diffuse nebula, and little seem to be known about it." and "...and the position and gaseous character show that it must be a galactic object."

The only star atlas I could find which had NGC 2899 mapped and listed was Verenberg-Blank's 'Handbook of the Constellations.', but it gives it as a diffuse nebula. The planetary nature of this object was first suggested by Henize in 1964, but we did not accept this until the mid-1970's. Looking at the images and the spectral profile, there is a strong red N II emission (at 658.4nm.), and no doubt the reason that NGC 2899 was first mistaken for a small emission nebula. Unlike the 90% of planetaries in colour photos that appear blue or greenish, this one is red. (Interestingly, this single N II line is also prominent in the red colour seen in some aurorae.) Readers may like to compare this spectral profile with other profiles seen in this series in the last month or two.

To improve contrast, observers with apertures >30cm. may like to attempt to use a light red filter on this object. Perhaps this may also reveal the 'butterfly' structure seen in the astrophotos.

Based on the nitrogen emissions, the literature states (Ie. IAU Symposium No.103; Peimbert and Torres-Peimbert (1983)) that NGC 2899 may be a candidate of a bipolar planetary Type I with extreme filamentary structure. They currently know only twenty-nine of these objects.

The central star is invisible to all amateur telescopes - even using a direct vision prism. ESO-Strasbourg catalogue states that the visual magnitude of the PNN is >15.9, while the photographic magnitude is >16.4. Temperature determination of the core star is difficult because of the lack of Helium lines; so a Zanstra temperature cannot be given.
NGC 2899 is approaching us at 3.0 kms^-1 towards us, while the nebulosity is expanding at c.+25kms^-1.
Statistical distances are estimated at 1.03± 0.3 kpc, and this even this is particularly uncertain.
In all, this planetary is easy to find and is a worthy object for moderate apertures.

SA3-10/ WRAY 17-31/ VBRC 2/ PK 277-3.2 (09314-5617) is a faint planetary some 34'min.arc. S.E.E. of NGC 2899. Discovered by Wray in 1966, it is a difficult object to see for telescopes below 25cm., however, its proximity to NGC 2899 makes it very easy to find. It appears, listed as SA3-10 as object #392 in AOST2, but it was not originally listed in AOST1. According to David Frew, this is a test object, and unless you are in dark sky with good seeing it is very difficult to see. He states;

"With a 30cm and an [OIII] filter the object appears as a faint but definite round haze of fairly even light about 2'min.arc. across. An equatorial triangle of moderately faint stars is superimposed on the nebula. This object shows the value of the [OIII] filter, as it is almost invisible without it."

The planetary according to AOST2 was first reported by Sanduleak in 1973, though most reference sources (Ie. ESO- Strasbourg Catalogue) suggest that J.Wray first discovered the planetary in his surveys in 1966.

I thought I could faintly see it with averted vision in a 20cm., though I obviously needed a bit more Pyrex! A 30cm. shows a near-perfect circular haze. So, they have classified it in the Vorontsov-Velyaminov system as a Type IV - ring structure, although there is not a real central hole.

The photographic image is remarkable, as it shows multiple rings. In the centre is an inner hole some 35"sec.arc. across. Further out is a brighter slightly squarish ring aligned along position angle 20^O that extends to about 100"sec.arc. It is this part of the nebulosity that we see visually in the telescope. Finally the 160"sec.arc. outer structure is thin but perfectly circular ring about 5"sec.arc. thick. I think a 50cm. Dobsonians with an O-III filter at a dark site might be just be able to see this.

Magnitude of the nebulosity is 14.6ph, while according to Steven Hynes' 'Planetary Nebulae' and Megastar 3.0, the PNN is 18.1. In size the planetary is some 1.8'min.arc. across, though the photographic image extends some 2.6'min.arc. Like NGC 2899, the NII intensity is larger than the O-III, while the measured expansion velocity is 28kms^-1. Other than this information, little is known about this object.

Surrounding Field of NGC 2899 and SA3-10.

The following objects Basel 20, R122, R120 and R119 lie in the same field as SA3-10. Also included is the bright cluster IC 2488 that is due south of NGC 2899, and FU Velorum.

R122 (09322-5601) (SAO 237078/ HD 82789) was discovered by H.C.Russell at Sydney Observatory using the17.5cm. (7¼") on the 18th March 1873. The magnitudes of this yellow and white pair are 8.4 and 10.2. Separation is 2.5"sec.arc. at position angle 110^O, and these values have slowly been decreasing since discovery. Right now it is uncertain if this is a physical system or an optical pair, but if it is a true binary, the period must be more than three hundred years. This pair will be interesting to watch over the ensuing decades.

Some 3'min.arc. west of R122 is R120 (09319-5602) (SAO 237073). Discovered on the same night as R122, Russell's original measures show a separation of 9.59"sec.arc. at PA 34.5^O Later observations of R120 show that Russell position angle was out by 180^O, a common problem facing double star observers. The current position angle is 215^O. Both are written as 10th magnitude, though later observations suggest the respective magnitudes are 9.2 and 10.2. I saw both colours as bluish.

Another fainter pair is R119 (09316-5602) is another 3'min.arc. further west of R120. Discovered on the same night as R122 and R120, the magnitudes of this duo are 10.6 and 11.5. The separation is a wide 17.0"sec.arc. at position angle 200^O. These last measures were taken 1934, and little has changed.

In all, these three pairs are contained in a starry background, and can be easily found some 42'min.arc. ENE of NGC 2899 or 20' NNE of SA3-10. A 10cm. is required to see these three pairs clearly.

FU Velorum (09337-5555) is a faint semi-detached eclipsing binary (EA/SD). located 1^O E.N.E. from NGC 2899. Photographic magnitudes change between 10.3 and 12.1p. in a period of 2 days 10 hours 35 minutes. This was first determined at Riverview Observatory, Lane Cove, NSW on the 2nd May 1937. The last serious observation took place in 1963. Little is known about the system, except that the primary is a white A0 star.

BASEL 20 (09325-5618) is an open star cluster placed 44'min.arc. SEE of NGC 2899, and is in the same field as SA3-10, some 8'min.arc. towards the east. (See middle left of Figure 3.) Telescopically it appears as a faint cross, and a first glance, it really does not look like a cluster. Proper motion studies by Lynga suggest the stars are physically connected, though other cluster experts caution doubt on its existence. The number of stars associated with the cluster is about twenty, covering about 10'min.arc, and the brightest stars in the 'cross' are around magnitude 12.5.

IC 2488/ Mel 97/ CR 208 (09275-5657) lies in Vela, a mere 5'min.arc. from the Carina border - literally on 'the ship's deck'. It can be quickly found some 52'min.arc. south of NGC 2899. (Figure 4) Easily visible in a 7.5cm., the cluster subtends 14'min.arc. The total integrated magnitude of the cluster is 7.4, and Lynga in his proper motion studies of IC 2488 determined that some seventy stars are associated. Cluster classification is given as '2 3 r -', saying that it is detached with a slight concentration, medium brightness and rich without nebulosity. Brightest star is the blue star B9 (SAO 237004; 09277-5700) at magnitude 8.9, followed by a yellow F5 star magnitude 9.3 (SAO 236995; 09272-5656) IC2488 contains many blue stars, and appears to me as various intersecting straight lines of stars moving north and south. Another solitary line is in an NW to SE direction. The two brightest components are contained within each line. It is likely that the yellow star is the centre of the gravitational potential, with the cluster's faintest stars ending at about magnitude 13.5. 6'min.arc.

To the northeast by 6'min.arc. is the faint magnitude 11.0 and 12.0 pair BRT 2548 (09281-5652). (Top left in Figure 4) Discovered by S.J.Barton in 1924, the solitary micrometric measure gives a separation of 3.6"sec.arc. at position angle 174^O. Using medium magnification to the eastern field is an orange K5 III star. This is the third magnitude variable star N Velorum (SAO237067) (09312-5702). Sky Atlas 2000.0 suggests it N Vel is a possible slow irregular variable star, while some observers classify it is CST - constant. The true nature or existence of this variable is unknown. Visual magnitude changes are said to be between 3.12 and 3.15, and this is even uncertain. Observers should use this naked eye star to enable them to find the cluster and PN's. N Vel is a mere 24"sec.arc. from being in the constellation of Carina!