IC 5148/ IC 5150/ PK 002-52.1 (21596-3923) (Grus) was first discovered by the Sydney amateur Walter Gale in 1894, near the ‘neck’ of Grus the Crane. For some reason it is not marked in Sky Atlas 2000.0 but does appear in the Sky Catalogue 2000.0! The planetary itself is found in a rather desolate field some 1.3^O West of Lambda ( ) Gruis. It takes at least a 15cm. to see the nebulosity, as the total visual magnitude is given as 13.0 while the photographic magnitude is a near equal 12.9. Unlike the majority of planetaries, this one is large c.120"sec.arc, as most of the literature states. Observationally, little difference is observed in the apparent size from the CCD or photographic images. A 20cm. clearly reveals its colourless annular structure, including a smallish 25" to 30"sec.arc. hole, and consequently, IC5148/IC5150 is classified as planetary Type IV. A 30cm or 40cm. starts to reveal some of the internal diamond-shaped ‘braded structure’, as seen in the images, with the eastern side appearing broader and brighter. Contrary to this, AOST1&2 obscurely states; "...and a considerable area looks paler (grey), but still luminous." This central hole is much smaller than most of the annular type planetaries. In theory, the appearance of a central hole is thought to be due to the radiation pressure pushing the surrounding gas away from the white dwarf core, leaving a ‘vacant’ space. It is likely that the development of annular structures is the last stage of planetary nebulae formation - before the object transforms into its solitary white dwarf phase. The planetary in three-dimensions is probably one, if not, two shells, that we are looking directly down the ‘poles’. Visually, the PNN is at magnitude 16.5 and can possibly be seen in a 40cm. or 50cm. telescope, though I have to admit that I have never seen it.

To my eyes, although the O-III filter image is slightly brighter, the observed spectrum is given as continuous. Usually, any object with a continuous spectrum has no advantage in using narrow-band filters.

Dennis di Cicco described it as; (S&T June 1986 pg.631);

"IC 5148 is a real show piece... With 280X and a UHC-filter, the 24" in Hawaii showed IC 5148 to be an exquisite giant ring, irregular with a dark centre and a 15.5 central star. Steve Gottieb of Berkeley California, observed it with a 13"-reflector and an O-III filter. He could view the nebula with direct vision and detect the dark centre with averted vision. This object is the same object as IC 5150."

(A nice image taken by him also appears on pg.632 in the same issue of S&T.)

Professional photography has revealed an outer halo exists that extends the diameter to about 135"sec.arc. Radial velocity measurements indicate that the nebulosity is moving towards us by some 23 to 28 kms^-1. Determined by the faint O-III emissions, the nebulosity has an expansion velocity of 53.4kms^-1 - one of the fastest expansion velocities of a planetary known. So far, the only adopted distance is 900 pc. (2 900 lty.) first given by Kingsburgh and English in 1992. The distance by them is stated as an upper limit and is based on the faint hydrogen-beta emissions. So far no further details on distance have been determined for this object - likely because of the faintness of the PNN.

It is surprising that Herschel actually missed this object. Even some of the more modern references, like Burnham’s, still do not list this object. As we have seen throughout this series, the common references for southern objects used by amateurs are inordinately incomplete. One of the notable problems with this object is that the IC catalogue gives it as two objects. Most references usually selected it as either IC 5148 or the combined IC 5148/5150. It was given these two different designations in the Dreyer’s ‘Second Index Catalogue of Nebula and Star Clusters, Containing Objects found in the Years 1995 and 1907.’ (Memoirs RAS LIX Part II) published in 1908. As mention before, Walter Gale discovered this object in 1894. IC 5148 and IC 5150 differs in position by 11"sec.arc. in right ascension and 62"sec.arc. in declination. IC 5148's position is taken from observations made by the veteran America observer Lewis Swift from an observatory on Echo Mountain near Los Angeles, and this planetary is featured in his list (MRAS, LIX pg.568 (1899)). Swifts’ positions were taken from images over very wide fields - having the general notoriety for having particularly inaccurate positions. IC 5150 refers to the position based on Gale’s observations. (His catalogue number 3246.) Dreyer’s ‘Index Catalogue’ also shows some confusion in their descriptions. Swift states the object as ‘vF, L, lE,*att.’, - very faint, large, little extended, star attached; while Gale states ‘pB, pL, annular’ - pretty bright, pretty large and annular. No confirmation was made between the two catalogues numbers, so the current designations remain. This is slightly unfair on Gale, because his description is closer to the truth.(See AOST1), and it is for this reason he lists it as IC 5150. Yet the preferred designation remains as IC 5148. In my view, this planetary is easy to find and is worthy of a glance.

Surrounding Field of IC5148/50.

HJ 5319 (22120-3819) is a bright yellow pair is located 1.7^O NE of Lambda ( ) Gruis. Herschel discovered this pair in 1836, and little has changed in the 2.1"sec.arc separation since this time. From the last measure in 1985, only the position angle has been found to have decreased from 110^O to 130^O. On the 10th October 1879, Hargrave, using the (18cm.) 7.25" Merz Refractor at Sydney Observatory, states that he could not find the pair (and he looked, in good seeing, several times in the ensuing weeks) - an amazing discrepance considering the aperture and the brightness of the two stars. The magnitude of the stars is given as 7.6 and 7.7. It would take a 15cm. to be able to separate the pair cleanly. Examining the proper motions of the two stars, it is uncertain if these two stars are associated.

IC 5175 (22128-3808) / IC 5174 (22127-3810) lie in the same field some 8'min.arc. NE of HJ 5319 (PA~280^O) are the two faint 14th magnitude galaxies, IC 5175 and IC 5174. whose centre is marked by a 11.4 magnitude star (GSC 7995:756) that lies between the two galaxies. Both were first discovered by Dr.Delisle Stewart in 1896-7 using a photographic 0.8m. (24") Refractor f/5.5 of the Harvard College Observatory from its Arequipa station in Peru. (Listed as #739 and #738, respectfully.) Eventually they were place in the Dreyer’s Second Index Catalogue (1908). Dreyer’s visual descriptions for the two galaxies are given as;

IC 5175 ‘eF,eS,R, bM’ - extremely faint, extremely small, round, brighter in the middle.

IC 5174 ‘eF,eS,cE 150^O’ - extremely faint, extremely small, considerably extended at PA 150^O.

IC 5175 has the brightest core of the two and should appear as a faint haze 1.0'x0.3'min.arc. around a small ‘east-west’ elongated core. More remarkable is the galaxy IC 1514, which is a barred spiral with a dramatic 1.3'x1.3'min.arc. ‘S’ shaped core, just visible in dark skies with a 30cm. The large extended arms are some 8'-9'min.arc. long in a north-south direction, and could be photographed by a long exposure using a 25cm. telescope. A 30cm to 40cm. is required to see both galaxies.

The STScI image show features that are mirror-imaged along paths of the spiral arms. Deeper images reveal that both galaxies are connected by a gravitational bridge. Each has similar high radial velocities’ c.11 500km.sec^-1, some 3% of the speed of light, suggesting they are indeed associated. Based on a Hubble Constant of 65kps.Mpc^-1, the distance corresponds to about 550 million light-years. IC 1514 arms have been calculated to be some 800 000 lty. in length, which is about seven times the width of our own Milky Way Galaxy! It has been speculated that this system is similar to M51, except that the separation is much larger and the galaxies are about a hundred times more massive!

HJ 5299 (21548-3926) is an equal magnitude pair 0.9^O to the SSW (6'min.arc. West and 30' South) of IC 5148. The magnitudes are 8.9 and 9.0, respectfully, and both appear yellow-orange as reflected in the late K0 spectral types. Later references state that the primary is a slightly hotter B8 subgiant. The pair is a wide 33.5"sec.arc, set at position angle c.56^O. It is clearly visible in a 7.5cm. telescope. Proper motions of each star makes this likely an optical pair.

SEE 466 (22050-3933) is an easily found faint pair placed 15.2'min.arc. (0.25^O) SW of the orangish Lambda ( ) Gruis. The magnitude of the pair is 9.3 and 10.0, respectfully, and I see each star as yellow and white. Separation is 1.8"sec.arc. - so a 15cm. or 20cm is needed to see it using medium magnification. I had to inspect three faint stars in the area really to identify it. Since the first measures in 1896, the separation has not changed, but the position angle has decreased from 10^O to 254^O between 1896 and 1976 at a rate of 14^O per decade. I examined this pair in 1994, and I estimated the PA at 230^O, and thought the separation just a little wider. Based on the proper motions and the changes in position angle, it is likely that the pair is a true binary. The period of the system estimated to be somewhere between 160 and 300 years.

He2-434/ PK 320-28.1 (19338-7433) (Pavo) lies in the far south of Pavo, 12'min.arc. of the border of Octans, and some 2.3^O SW from the star Epsilon ( ) Pavonis. It is inconveniently not listed in Burnham’s or Sky Atlas/ Catalogue 2000.0. Located within a barren field, He2-434 is both difficult to find and see. A 30cm. using a 26mm Plossel with a field of 38.4'min.arc. - the brightest field star visible is magnitude 10.7. The planetary is particularly faint, not obvious, taking the integrated photographic magnitude of 12.1. Using a 30cm. the nebulosity is just visible, though a 40cm. or 50cm. would give a much better view. To the northern edge is a bright portion of nebulosity that is easily apparent when using the O-III filter. I thought I could see this with averted vision and without the filter. The remainder of the nebulosity is faint, though a small knot some 7"sec.arc. from the stellar core lies to the south-east at about PA 220^O. I particularly like this planetary because of it odd shaped nebulosity and the challenge just to find it!

The visual diameter is some 10.1"sec.arc. with an expansion velocity is 5 or 6 kms^-1. Magnitude of the central star is 14.9, and is likely just visible in a 40cm. telescope. The Zanstra Temperature of the core has been recently determined as 33 000^OK, which is unusually cool for a PNN. Little is known about this planetary and a distance has yet to be found out.

Surrounding Field of He2-434.