Palomar Globular Clusters - The Delaware Valley Amateur ...

SEVENTH H AVfN I TIDAl TAlE I lY APN I A' OM nc
THE QUARTERLY JOURNAL OF
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AI Lamperti
Globular clusters are some ofthe oldest deep-sky
objects, having formed during a galaxy's final
condensation. As a result, they are also quite a
distance from the center of the galaxy and are
often found in the galaxy's halo. Many globular
clusters can be seen in the Milky Way and even
the globular clusters in our nearby neighboring
galaxies are wi thin the reach of amateur
telescopes.
The Palomar globular clusters were found on
the plates ofthe Palomar Observatory Sky Survey
taken with the 48-inch Schmidt telescope in
1950s. There are 15 clusters on the list. David
Ratledge wrote a comprehensive history with
images of each of the globular clusters.!
Many observers have reported their findings,
e.g. Barbara Wilson. 2 However, a search of The
Deep-Sky Observer Index only found two articles
on Palomar 2 by Maurice Gavin 3 and Steve
Gottlieb 4 Recently, an observing buddy of the
author,Joe McCormick from the Delaware Valley
Amateur Astronomers, asked if I had ever seen
any of the Palomar clusters. A quick review of
an electronic database indicated all were seen,
some twice, save for two. Those two were
immediately added to the list for the next
observing session. The following descriptions
were made by the author with 13-inch, 18-inch
and 20-inch f/5 Dobsonian reflectors from dark
sky sites in Pennsylvania, w ith one made in
Weston, Vermont.
Palomar 1
20-inch f/5, 272x
To find it, I needed the
Millennium Star Atlas to
star-hop. The cluster was
seen with direct vision
under a triangular asterism.
There may have been
some resolution as a
couple of stars were
discernible. Estimated
Globular Class XI (actually
XII).
Palomar 2
20-inch f/5, 272x
This was observed on the
same night as Palomar 1.
The Millennium Atlas
helped. It makes an
equilateral triangle with two
stars, with Palomar 2 at the
apex. It is a hazy patch
and not quite resolvable.
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Palomar 3 (left)
18-inch f/5.17, 177x & 256x
This was a very small, very
faint globular cluster and
not resolvable.
Seven years later: 20-inch f/
5,272x.
I needed the Millennium
Atlas to find it.
It is small with no
resolution, like a round
galaxy.
Palomar 4 (right)
20-inch f/5, 272x
It is located on the border
of Coma Berenices and
Ursa Major. This was a
hard one; very faint, like an
out-of-focus star.
Palomar 5 (left)
18-inch f/5.17, 256x
Looks like a faint galaxy
with no resolution.
Seven years later: 20-inch f/
5, 272x.
This was difficult to see
and needed averted vision
(scale 3) . Also I needed
jiggling of the telescope
and a cover over my head.
It was a very faint hazy even
glow in the area indicated
by the atlas.
No resolution seen.
Palomar 6 (right)
20-inch f/5, 272x
This one needed an averted
vision scale #2. It was a
hazy, faint glow with no
resolution seen.
Palomar 7 (IC 1276) (left)
20-inch f/5, 313x
I could only make out a
handful of stars: 3 bright
ones and a couple of dim
ones. There are probably
more that are fainter.
Palomar 8 (right)
18-inch f/5.17, 286x
It looks like a faint galaxy.
Eleven years later: 20-inch
f/5, 313x. I would have
missed it except the image
showed the star field. It is
small, like a minuscule
open cluster.
23

Palomar 9 (NGC 6717) (left)
13.1-inch f/5.17, 70x & 240x
This globular cluster is a
Herschel object (111-143)
and was fairly bright and
just about resolvable. It
reminded me of a galaxy.
Palomar 10 (right)
13.1-inch f/4.5, 130x
Averted vision and shaking
of the telescope slightly
showed a small, faint,
round glow with no
resolution.
Nine years later: 20-inch f/5,
313x. This time it was seen
with direct vision but it still
appeared as a round glow
with no definition.
Palomar 11 (left)
20" f/5, 272x
A bright star on the edge of
the globular as seen in
Uranometria was a clue.
With that star off the edge
of the field, a grouping of
stars seems like an open
cluster. Estimated Globular
Class XII (Really = XI) . .
Palomar 12 (right)
20" f/5, 313x
This was easy to find
adjacent to a small
asterism triangle of 3 stars.
It appeared as a fainter
glow adjacent to the
asterism. Only a handful
of stars were discernible.
Palomar 13 (left)
20" f/5, 272x
The Millennium Atlas was
helpful to decipher the
fainter stars in an asterism.
The globular was seen with
averted vision (scale 1) as
a hazy glow with no .
resolution.
Palomar 14 (right)
20" f/5, 272x & 416x
This was a tough one. At
best it was an averted
vision (scale 3) . I saw it
fleetingly twice, once urider
416x. It was found in an
area indicated by
Uranometria.
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Palomar 15
20" f/5, 272x
This appeared as a milky
area seen with an averted
vision (scale 2).
Photographs confirm
ocation.
Although the Palomar globular clusters are an ideal
observing challenge, o ne may w ish to push the
envelope a bit further by observing a list of extreme
h alo clusters. These are all at least 70 kiloparsecs
(228,000 li ght years) fro m the Sun and include
som e of the Palo m ar clusters. Barbara Wilson
again has demonstrated her knowledge and skills
in her descriptio ns of theseS
References
[1] http://w ww.dee p-s ky.co. u k/ o bserv ingl
palglobs/ palglobs. htm
[2] http: // a s t r o n 0 m y - m a I I . c o m I
Ad ve ntur es. In,D ee p . Sp a c e l
palglo b.htm#tips
[3] 'G lobular Star Cluster Palomar 2', Maurice
G av in WSQJ 88: 48 April1992
[4] The Visibility ofPalomar 2', Steve Gottlieb,
WSQJ 90: 44, O ctober 1992
[5] http :// a s t r o n 0 m y - m a II . c o m I
Adventures.In.Deep,Space/obscure2.htm
No. Const.
1 C ep
2 Aur
3 Sex
4 UMa
5 Ser
6 Oph
7 Ser
8 Sgr
9 Sgr
10 Sge
11 Aql
12 Cap
13 Peg
14 Her
15 Oph
The Palomar Globular Clusters
RA Dec. Mag. Size Class 1 Distance l
033320.6 +793456 13.6 1.8' XlI 150
044605.8 +312255 13.0 1.9' IX 114
100530.9 +000415 13.9 2.8' XlI 313
112915.8 +285823 14.2 2.1' Xl1 304
151605.3 -000641 11.8 6.9' XlI 70
174342.2 -2613 21 11.6 7.2' Xl 10
181045.7 -071242 10.3 7.1' XII 42
184129.9 -194933 11.2 4.7' X 1
18 5506.2 -224203 9.2 3.9' VIII 52
191802.0 +183422 13.2 3.5' XlI 2J
194514.4 -080026 9.8 3.2' Xl 36
214638.9
230644.5
-211510
+124619
11.7
14.5
2.9'
1.8'
XlI
XlI
1610 59 +145730 14.7 2.1' XlI 2+J.
165951.1 -003200 14.2 11')..-9' XlI .L
62
-",
Data obtained from Deep Sky Browser (http://www.messier45.com)
I
Hogg, Helen Battles Sawyer, 'Harlow Shapley and Globular Clusters'. PIlb/i,a/it'lL; . ~f ,"e
Astrollomical Society ofthePacific 77 (458): 336-46, 1965. (Basically; Class I is giH'U [Q he c1u_ rers
with the highest concentration and XII to the clusters with the lowest concenrrari n.
2 X lO'lJight years
25