The False Cross

As many objects are faint, a dark sky and preferably a telescope of 20cm aperture or greater is needed. Iota Carinae is an F-type supergiant star of around 5200 times the brightness of our Sun. This magnitude 2.2 intensely hot star is also known as Aspidiske from the Roman Scutulum or Little Shield.

A little east of iota lies our first target, the tiny planetary nebula catalogued as P 278.6-6.7. This planetary nebula as well as others that follow are taken from the Strasbourg-ESO Catalogue of Galactic Planetary Nebulae. Also known as He2 26 and appearing as a 12th magnitude star to the telescope, an O III (oxygen) filter will help in determining its planetary nebula status.

Far easier is NGC 2867 to the north northeast. Spanning 18"x16", this magnitude 9.7 planetary nebula appears as a bright star at low power. Increasing the power to 100 times or greater will show a small and bright disk. NGC 2867 is one of Sir John Herschel's discoveries from the Cape of Good Hope. Believing this object to be an actual planet, he measured its position among the surrounding stellar background to try and determine any motion. In his written account of 01 April 1834, he recorded:

"The finest planetary nebula I ever remember to have seen for sharpness of termination; 3 arcsec diameter; exactly round; no more haziness about them than would be about a star of the same magnitude to-night (which is a favourable one) Light, a pale white = star of 9th mag. Position of companion star = ... 58.6 ; star = 15th mag. A very remarkable object. Showed to Stone, who distinctly perceived the total difference of appearance between it and a star 9th mag very near it. A second companion star suspected (at about half the distance of the 1st by diagram, and at an estimated position of 330 ) among multitude of large and small stars."

The next night he recorded:

"Observed with Mr. Maclear, April 2, 1834, out of the meridian. Quite round, well defined, and about 3 arcsec or perhaps 4 arcsec diam. Much better seen (between clouds) than last night. The small star is still 1.5 diam. from edge. It has therefore not moved perceptibly, and is therefore not a planet."

Hartung recorded NGC 2867 as:

"This bright pale blue planetary nebula lies in a field profusely spangled with stars; it is round, about 8 arcsec across, of very even light with no visible central star. Even a three-inch [telescope] will pick it out easily from the field..."

Just over halfway along and east of a line joining iota Carinae with kappa Velorum lies the bright star N, right on the border joining these two constellations. To the south lies the planetary nebula P 278.5 -4.5. Also catalogued as He2 32, this very faint object of average surface brightness 15.0 needs a large aperture to detect its 45"x27" disk.

IC 2488 is a large and loose open cluster west of N, its white 10th magnitude and fainter stars spread over 10'. Binoculars will show an unresolved hazy glow, telescopes needed to bring out the individual members. Discovered by Lacaille in the 1750s, he saw it as "a faint star in nebulosity" in his primitive 0.5" telescope. Two prominent lanes of stars run north-south, separated by an absence of stars.

P 277.7 -3.5, also Wray 17 31, is a faint and large 110" disk at low power, an OIII (oxygen) filter helps but higher magnification hinders observation of the object. Best at lower power, look for this delightful surprise north of star N.

Northwest of Wray 17 31 lies another planetary, NGC 2899. Lying around halfway along a line joining N and kappa Velorum and just east of a 7th magnitude star, this is another of Sir John Herschel's discoveries. He recorded it as:

"faint, pretty large, round, gradually a little brighter in the middle; 80 arcseconds. At least 80 stars in the field."

Burnham summarizes this nebula as:

"pretty large, pretty faint, round, diameter 1.5', in rich field 1.3 southeast from Kappa Vel."

Hartung writes:

"This field is lovely, sown with fairly bright stars on a profuse faint background. In it is an irregularly round luminous haze about 1.5' across, rising broadly to the centre...a 6-inch telescope will show the nebula but its location needs care."

Kappa Velorum, also known as Markab, shines at magnitude 2.4. This B-type subgiant lies around 500 light years away and throws out 1900 times more light than our Sun. Just to the northeast of kappa lies our next target, P 275.8 -2.9, also He2 2 29. This planetary will display a tiny disk 14" in diameter at around 100 times magnification with a filter. At magnitude 13.3, its small size give sit a fairly bright surface brightness of 10.1.

P 275.2 -3.7, also He 2 25 lies to the northwest of kappa, just south of a magnitude star. High power will show a faint stellar glow, nothing to write home about but rewarding if only for the sake of detecting it.

P 275.0 -4.1, also PB4 lies west of kappa, its tiny stellar disk paired with a faint star. Definitely one for the OIII filter.

P 275.3 -4.7, also He 2 21 lies southwest of kappa, showing as a faint star though high power and an OIII filter will show its planetary nebula status. A triangle of faint stars lie near.

P 275.2 -2.9, also He 2 29 sits north of kappa, showing as a faint star-like glow at high power.

Moving on to delta Velorum, we find a magnitude 1.9 A-type white main sequence star. With a luminosity of 70 Suns and a distance of around 75 light years, it appears to share the same proper motion across the sky as Sirius and a number of other bright stars, this group known as the Ursa Major Stream. Delta has a close companion of magnitude 6.0 that can be resolved with high power. Another star of the 10th magnitude lies 69" away and can be resolved into two stars of magnitude 10.5 and 13.0, separated by 6".

To the north and slightly west lies omicron Velorum, a 3.6 magnitude B-type star surrounded by a large scattered group of bright, young white stars known as IC 2391. Discovered by Lacaille, this naked eye open cluster contains very few stars, around 20 or so and a widefield eyepiece is needed to capture it. Triangular in shape, it has a number of double stars, one of which can be separated in steadily held binoculars.

Nearby to the east lies NGC 2669, a large open cluster with around 40 faint stars of 10th magnitude and fainter. Discovered by Sir John Herschel, NGC 2669 lies in a superb stellar field.

East northeast of delta lies another planetary nebula, P 272.4 -5.9 also known as MeWe1 1. Catalogued at magnitude 15 and a size of 110", expect it's surface brightness to be faint. Large apertures and an OIII filter are possibly needed here.

NGC 2640 lies southwest of delta, a small and reasonably bright galaxy discovered by Sir John Herschel. A 30cm and larger mirror may show a bright knot in the eastern region. Three 14th magnitude stars are near on the western side. NGC 2640 sits between a 10th magnitude star to the northwest and a 9.3 magnitude star to the southeast.

Epsilon or Avior shines at apparent magnitude 1.8 and is a K-type bright orange star with a computed luminosity of 1400 Suns. To the east and slightly south lie the faint galaxies ESO 124-18 and ESO 124-19. Both have a photographic magnitude of just under 15 but a 30cm mirror should cope with this pair. Aligned east-west, these associated twins show as a small and faint nebulous wisp.

ESO 124-15 is another faint galaxy 1.5 degrees south of epsilon. This barred spiral should be seen in a 20cm mirror and gently rocking the telescope can help in detection as faint moving objects stimulate the eye more than faint still objects. Look for two pairs of faint double stars 7'.6 south of ESO 124-15. The first double h4096 has components of magnitude 10 and 12.5 and are separated by an easy resolvable 15".2. The second double h4097 has a primary of 10th magnitude with a companion of magnitude 11.4 separated by 11".0.

R84 is a lovely yellow equal pair 27'.0 northeast of epsilon. Discovered by H. Russel in 1881, the stars have slowly widened their separation from 7".7 to 8".9. Their magnitudes are easy for smaller mirrors at 10.46 and 10.53 and lie around 26.8 and 24 light years from our Sun. Also in the same field is I 801, 22'0 southeast of the above pair. I 801 is the brightest of a number of magnitude 9-10 stars in the eyepiece field. Discovered by R. Innes in 1910, high power of 300x or so will separate this magnitude 8.6 star into close components of magnitude 8.8 and 10.

HJ 4084 is a beautiful triple system discovered by Sir John Herschel in 1836. Situated 41'0 northwest of epsilon, the brighter two components have magnitudes of 6.5 and 9.8 separated by a respectable 42".4. A closer look at the fainter member will show a close companion of magnitude 9.9, just 3".1 away. A field star of magnitude 10.4 lies 1'.3 away to the southwest.

A beautiful colour contrast pair of blue and yellow stars lie 1 degree southwest of epsilon Carinae. Probably not connected in any way, their magnitudes of 7.3 and 7.8 and wide separation of 2'.2 are a delightful surprise to the eye.

A line from kappa, passing through epsilon points directly to an easy naked eye haze. Binoculars will show a glorious sight, a large and brilliant open cluster, NGC 2516. A wide field eyepiece barely contains this group, the stars scattered far and wide and a bright orange star lies near the central region. Around 100 stars are seen, ranging from magnitude 7.0 and fainter. This cluster has an age of around 110 million years, middle-aged if you like and contains a smattering of yellow and orange stars.

There are a number of double stars within this vast stellar city and around 10 should be available to a 20cm mirror. Use 100x magnification or above and inspect each star closely. You may be pleasantly surprised.

Sir John Herschel recorded it as:

"a star 6th magnitude, in a superb, very large cluster. Rich and brilliant. In the northern part about 20 seconds; following this star is a star of 5th magnitude, ruddy. Has two or three neat doubles in it. The whole region is rich in large stars."

North of NGC 2516 lies a large and faint reflection nebula, IC 2220, commonly called the 'Toby Jug Nebula'. Its name comes from its bipolar shape, the illuminating star HD 65670 (V341) a red supergiant irregular variable that shines between 6th magnitude at brightest to 7th magnitude. Mass loss has contributed the dust seen here and silica is thought to be the main ingredient of this dust cloud. CCD cameras will have the best luck here as IC 2220 is visually difficult even with large mirrors and a nebula filter should pull it from the background sky.

Take the time to explore this wonderful region well. With the eye drawn ever eastward toward the rich bounty of the eta Carinae Nebula and surrounding playground of stars, dust and gas, it would be a shame to at least not sample the delicate treasures of the False Cross.

Open Clusters

Double Stars

Planetary Nebulae

Galaxies

Nebulae