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(IAAC) FWD: [Deep Southern Deep Deep-Sky Observations!]



[
 Obviously I thought this post was very appropriate indeed! Here are Auke's 
outstanding observations... I'll try to reformat individual observations next 
week for regular submission. Enjoy all!
 -Lew
]
Hi Lew,
I've attached an e-copy of the yet to be published April newsletter of our 
deepsky section. Rather than posting it to -announce, I 'd rather let you 
decide on its suitability; perhaps it has a too far southern content?
Regards,
Auke
-------------------------------------------------------------------------
Auke Slotegraaf    :    auke@global.co.za    :  =20
http://www.global.co.za/~auke Box 12838,Stellenbosch,7613,South Africa :
Tel 27+21+8873427 : Nullius in verba MNASSA (mnassa@saao.ac.za) :  1st
Ghost Atlas of S.Africa (ghosts@mindless.com) AD&D DM : 550 LTD : Origins
& functions of paranormal belief : Deepsky observer
- - - - - - - -
Nightfall - Newsletter of the Deepksy Observing Section, ASSA. April 1998
From: Mon. Notes Astron. Soc. South. Africa, vol 57 (3&4), April 1998
The stretch of Milky Way from Sirius to the Pointers contains some of the
most  brilliant open clusters in the night sky, easy pickings for even th=
e
most casual  binocularist. Here are numerous brilliant stars, too, formin=
g
easily recognised  constellations and asterisms. Starting at the Pointers=
,
and moving up the Milky Way to  Sirius, we encounter Crux, the Diamond
Cross, False Cross, Southern (right-angled)  Triangle, and finally Canis
Major itself.
The Southern Right-Angle, although not an "official" asterism, is
nevertheless easy  to make out. It consists of Lambda and Gamma Velorum
and Zeta Puppis. The star at  the eastern tip of the Triangle is Lambda
Velorum (Alsuhail), a 2nd magnitude star  that is a convenient
starting-point for a star-hop to some fascinating clusters. To my naked
eye, Alsuhail has a distinct orange-yellow colour; what do you see?  The
region surrounding this star, specially to the south and east, shows as a
large  mostly resolved glow, to one side of the Milky Way. It appears to
be bound on the east  and west by two massive, dark Milky Way dust lanes.
In binoculars, the colourful  Lambda is accompanied by a 4+ degree field
of a dozen bright, scattered stars making  an attractive sight.
The patch of sky east of Alsuhail, bound by RA 9h12m to 10h and
declination -39   to -50 , corresponds to chart 398 of the Uranometria
2000.0 atlas. On this chart, three  open clusters (NGC 2982, NGC 2849 &
Pismis 12) and a planetary nebula (NGC  2792) are plotted. Of these, only
NGC 2982 can be seen in binoculars.
NGC 2982 lies nine degrees east of Alsuhail. It was first noted by Sir
John Herschel  during his 19th century visit to Cape Town. Observing from
the foot of Table  Mountain, he recorded it in his observing log as "a
cluster of about 20 stars 11th mag  and two of about 10th mag, forming an
oblong nearly in parallel; place of preceding  star about 10th mag." By
"oblong nearly in parallel" he means the grouping is  elongated in an
east-west direction.
When the New General Catalogue (NGC) was reworked in the 1970s as the
Revised  New General Catalogue (RNGC) authors Sulentic and Tifft declared
this cluster to be  "non-existent", recording that it was not a true
stellar grouping. Be that as it may; it is  clearly visible in binoculars
if the sky is good. From typical light-polluted suburban  skies I recorde=
d
it in 11x80's as "Only a 10th magnitude star, with possibly an  extension
due east." Under darker skies (limiting magnitude 5.5 to the naked eye),
but  with noticeable haze, I imagined seeing a nebulous puff here. Some
attention, using  averted vision, shows at least two faint stars
surrounded by a glow. Under even darker  skies, with greater transparency=
,
binoculars show it more clearly. The cluster is easy to  find midway
between two 6th or 7th magnitude stars, one of which is y Velorum. It is=20
seen as an indistinct smudge about 10' across. Under mediocre conditions,
it appears  irregularly round and with great attention looks elongated
roughly southeast -  northwest. However, under excellent conditions and
when well dark-adapted, this very  faint, hazy object is clearly elongate=
d
east-west, in the ratio 1:2. The surrounding 4   binocular field is rich
and textured and the cluster doesn't have enough contrast to  stand out
well.
The key to this cluster is aperture. Even a 6-inch will show it well. A
low-power  (42x, 50' field) eyepiece shows it clearly as a coarse groupin=
g
of about 15 stars of the  11th magnitude; it fits snugly into a 15'
compass.=20
The other two open clusters, NGC 2849 and Pismis 12, are far more obscure=
;
I'd be  keen to hear what other observers find here.
A short distance north-east of Alsuhail is the planetary nebula NGC 2792.
Don't  bother looking for this one in binoculars - it's catalogued at 13t=
h
magnitude. However,  don't be discouraged if you have a telescope - it
appears somewhat brighter visually  and I expect it to be visible in a
4-inch.=20
At low power, a 6-inch shows it readily as an 11th magnitude star on a
rich field of  mixed magnitudes. Higher magnification brings out the pale
round disk, which appears  featureless. (Look for the neat tiny double
star nearby). Greater aperture shows it as an  intriguing object. John
Herschel again: "observed with Mr Maclear and another  gentleman . . .
pretty faint, exactly round, equal to a star 9th mag, but of a dull light.
At  first I was inclined to think it double, but with 320 [magnification]
it exhibited a  uniform round disc; nor did a friend to whom I showed it
see any division. Stars to-
night perfectly well defined." On a different night, he called it "pretty
bright, round, 6  arcseconds diameter, equals in light a star about 9th
mag, a very careful and good  observation." He recorded it a third time,
and wrote in his log: "Viewed past meridian.  It occurs in a field with
about 40 stars. Diameter 4 or 5 arcseconds at the utmost; 10  arcseconds
is too large certainly . . . the night is good and it bears magnifying.
With  320 power the disc is dilated into a dim hazy round nebula; yet
there is a peculiarity in  its appearance which completely separates it
from all nebulae of the same size. A very  remarkable object."
Although these are the only objects plotted on the Uranometria chart,
there are  several others that can be picked up in this part of the sky.
Several of these objects were  first recorded in the 1970s by astronomers
working at Uppsala Observatory, examining  photographic plates taken with
the European Southern Observatory's 1-metre Schmidt  telescope at La
Silla, Chile. Also known as the Quick Blue Survey, it was designed to  be
a counterpart to the more famous northern Palomar Observatory Sky Survey
(POSS).  One of these new objects is ESO 315 SC 14. This little cluster
lies north-east of Psi  Velorum, and is readily seen with a 6-inch
telescope on a moderately busy field.  Although small (3'), it is quite
noticeable and clearly fuzzy even at low power (42x).  Use high powers to
show it as a single 10th magnitude star surrounded by five much  fainter
starlets. Larger telescopes should show a handful of even fainter members=
=20
(image on previous page).
A far more obscure object is ESO 212 SC 2. In my 6-inch it is as invisibl=
e
as the  Galactic Equator near which it lies. This cluster is also listed
as vdBH 63, indicating  that the Uppsala team wasn't the first to spot it.
Instead, it was discovered by Canadian  astronomers on a photographic
plate taken with the Curtis-Schmidt telescope of the  Cerro Tololo
Inter-American Observatory. In the van den Bergh-Hagen catalogue,  which
was drawn up after these plates were studied, it is described as being
moderately  rich and 1.5 arcminutes in diameter. If you have any luck
spotting it, please let me  know.
The cluster ESO 261 SC 7 is an altogether more obvious target. At 52x, th=
e
40' field  of my 6-inch shows about thirty 10th magnitude stars in the
field, and then some 30  more fainter ones. Although it is widely
scattered, it is a somewhat suspicious field,  suggesting the presence of
a real cluster. If all the stars were 3 or 4 magnitudes  brighter, it
would resemble NGC 2516 or IC 2602.=20
Look six degrees further east for Ruprecht 81. It is visible in the same
low-power  field as NGC 2982, and is about a third of its size. It is
readily seen in the 6-inch as a  small, irregularly round glow, 10 very
small stars (perhaps more), resembling a very  distant open cluster. It i=
s
elongated southeast-northwest and measures just under 3' x 1'.  It remind=
s
me of the Beehive (M44) seen with the naked eye.
Further south lies NGC 2932, another of John Herschel's discoveries. He
wrote:  "This is about the middle of an enormous cluster of a degree or
degree and half in  diameter, very rich in stars of all magnitudes, from
8th mag downwards, which merits  registry as a sort of telescopic
Praesape. It may perhaps be regarded as a detached  portion of the milky
way, which is here very much broken up." The verdict of the  compilers of
the RNGC is a thumbs-up: there is no real cluster here. On the one hand,=20
I'm inclined to agree; I searched the area with the 6-inch and a 50' fiel=
d
of view, and  found nothing resembling a large cluster. On the other hand=
,
binoculars do seem to  show a large stellar congregation. Tripod-mounted
11x80's show a vague, coarse  gathering of about 10 stars, =BD  across, o=
nly
somewhat separate from the background.  These few stars are fleshed out b=
y
"nebulosity" between the members. By comparison,  within the field, just =
1=20
west-southwest, lies a brighter grouping of stars, same size, but=20
distinctly free of its neighbour's haziness. The whole area, for at least
3  around, is  littered with fine, small stars, making a milky rich field.
Let me know what you see.
Due east of NGC 2932 lies an interesting binocular field, surrounding the
orange-
yellow star m Velorum (mv =3D 4.6, near 09:52, -46 .5). Here, a noticeabl=
e
if sparse  stellar grouping of a half-dozen white brightish stars
accompanies the one coloured  member. Look close to m for a small
companion, which has the appearance of colour. I  suspect this is merely
an illusion, because of its proximity to the coloured star, and also=20
because it is probably too faint for colour detection anyway.
South of this field lies Ruprecht 160, which the 6-inch plainly shows as =
a
coarse, 6  arcminute small-starred grouping. At 144x, there are two 9th
magnitude stars (shown  on the Uranometria) and then about half a dozen
fainter ones arranged in an east-west  elongated grouping (image on page
2).
Pismis 15 to the south-west is clearly out of reach of my 6-inch; as the
image  shows, it is a moderately rich but indistinct grouping of very
faint stars, not well  separated from the background. I haven't been able
to check out this cluster with a  larger telescope, and welcome any
observations of it.
The final unplotted object is vdBH 60. This cluster is described by van
den Bergh and Hagen  as being 2.5' in diameter, and star-poor. Its
position is somewhat similar to that of Pismis 11,  differing by 13' in
RA, and 18' in declination. The description of Pismis 11 is a closer
match:  2' in diameter, circular, and containing 18 stars. I'd bet on it
that these two objects are the same.  The image below shows a 15' x 15'
patch of sky around the co-ordinates reported by van den  Bergh and Hagen=
;
there is a clustering of stars south of the bright star. I'd be keen to
hear how  this grouping appears visually.
As always, correspondence is welcomed at PO Box 12838, Stellenbosch, 7613, or 
via  email to auke@global.co.za
ID         Other names  RA  (2000.0)   Dec     Diam    Object type
NGC 2792, ESO314-PN6    09:12:25    -42 22.9'   0.2'   Planetary nebula
vdBH 60                 09:15:47    -49 59.0'   2.5'   Open cluster
Pismis 11,ESO211-SC8,vdBH 60? 09:16:41 -49 42.6' 2'   Open cluster
NGC 2849, Collinder 207 09:19:23    -40 31.0'   2.3'   Open cluster
Pismis 12, ESO261-SC5   09:19:58    -45 06.7'   4.5'   Open cluster
vdBH 63, ESO212-SC2     09:20:36    -49 13.4'   1.5'   Open cluster
ESO261-SC7              09:24:20    -44 42.4'   33'    Open cluster
Pismis 15, ESO212-SC10  09:34:43    -48 02.3'   4.5'   Open cluster
NGC 2932                09:35:16    -46 57.0'   1.5 ?  "non-existent"
ESO315-SC14             09:35:24    -39 32.0'   3'     Open cluster
NGC 2982, Ruprecht 80   09:42:02    -44 00.8'   10' ?  Open cluster
Ruprecht 81, ESO262-SC3 09:45:10    -44 06.0'   5'     Open cluster
Ruprecht 160,ESO262-SC11 09:56:21   -47 02.1'   1.7'   Open cluster
--------------------
Auke Slotegraaf
Director: Deepsky Observing Section, ASSA