Palling Around With Palomar Globular Clusters

The intriguing Palomar globular clusters will challenge observers with modest to large telescopes, while providing a satisfying ramble around the galactic halo. Seize the upcoming dark of the Moon to make their acquaintance.

Keeps On Ticking

Scott Kardel, public affairs coordinator for Palomar Observatory, stands at the 48-inch Schmidt camera used for the first Palomar Observatory Sky Survey in the 1950s.
Sky & Telescope archives

Back when the Palomar clusters were discovered, a Coke cost a nickel and a quarter would buy you a burger at a Mom-and-Pop diner. We currently know of about 157 globular clusters in Milky Way galaxy, 15 of which were discovered on the survey plates of the first Palomar Observatory Sky Survey (POSS) in the 1950s.

The astronomers who identified this globular subset named for the famous observatory are some of profession's most famous practitioners including Edwin Hubble, Walter Baade, Fritz Zwicky, George Abell, Milton Humason, and Halton Arp.

All but two — Palomar 7 (IC 1276) and Palomar 9 (NGC 6717) — had never been seen before, and with good reason. Palomar 6, 7, 9, 10 and 11 are heavily obscured by interstellar dust along our line of sight, while several others, including Palomar 3, 4 and 14, inhabit the remote outer halo of the galaxy. Despite their size, distance robs them of their radiance. When it takes a 48-inch Schmidt camera to dig these out, you know they're objects to be reckoned with.

Cast of Sparkling Characters

Meet the crew! These are the 10 featured Palomar globular clusters we'll explore in this article. All images are from the Digital Sky Survey. North is up and each square measures 10′x10′ across. Click to enlarge.

Fortunately, not all of the globular clusters present an impossible challenge. A couple are visible in 8-inch scopes and most in a 16-inch. Palomar 9 is surprisingly bright and was first spotted by none other than William Herschel on August 7, 1784, long before the hamburger was even invented.

Golden Globe

Palomar 7 is not only one of the brightest in the bunch but it's also relatively easy to resolve into individual stars.
Gregg Ruppel

Ditto for IC 1276 (Palomar 7), first seen by American astronomer Lewis Swift of comet fame in 1889 and independently rediscovered by George Abell in 1952 during the survey.

The clusters range from easy-peasy Palomar 9 at magnitude +9.3 to the eye-numbing Palomar 14 at +14.7. Many are found in the summer sky, so we'll concentrate on those, making good use of the upcoming "dark window" when the bright Moon departs the scene starting about August 21st.

My observations were made with a 15-inch (37-cm) reflector under Bortle 3-4 skies (rural to rural-suburban transition) in early August. Of the 10 globular clusters attempted, I saw seven, suspected one and was defeated by two. I hope my notes, along with the finder charts created by amateur astronomer Alvin Huey, will prompt you to pursue these faint but fascinating objects that dot our galaxy's exoskeleton like lanterns in the night.

* Palomar 5 in Serpens (R.A. 15h 16.1m, Dec. –00° 07′): Magnitude 11.8, Diameter 8′: Located ½° south of 6th-magnitude 4 Serpentis. Nothing visible at 64× magnification. Increasing the power to 142× and 245×, I caught hints of a relatively large, misty patch using averted vision. Extremely faint. No stars or granulation noted.

* Palomar 6 in Sagittarius (R.A. 17h 43.7m, Dec. –26° 13.3′): Magnitude 11.6, Diameter 1.2′: Too low from my location and compromised by light pollution. Not visible ... at least this time around!

Rich Cluster In A Rich Field

This color image of Palomar 8 nicely captures its granulated appearance in the telescope.
Anthony Ayiomamitis

* Palomar 7 in Serpens (R.A. 18h 10.7m, Dec. –07° 12.5′) : Magnitude 10.3, Diameter 8′: This large, easy cluster jumped out right away at 64× and was well-resolved with a magnification of 142×. I could see lots of faint twinkles across its core along with a bright 13th-magnitude star anchoring the cluster's northeastern border.

* Palomar 8 (R.A. 18h 41.5m, Dec. –19° 49.5′) in Sagittarius: Magnitude 11.0, Diameter 5.2′: A scrap of fog about 2′ across easily visible even at 64×. Upping the magnification to 142× and using averted vision, the cluster appears granulated with little central concentration. 242× reveals a clumpy appearance with a good number of very faint stars resolved at the limit of vision.

* Palomar 9 in Sagittarius (R.A. 18h 55.1m, Dec. –22° 42.1′): Magnitude 9.3, Diameter 5.4′: Absolutely fascinating object! Located immediately south of and in the glare of Nu2 Sgr, a beautiful 5th-magnitude gold-colored star. Although the listed size is over 5′, I saw a much smaller clump of gems a third as big shaped like a king's crown. A magnification of 142× did a nice job showing about a dozen distinct stars. Averted vision and higher magnification added a few more. You'll enjoy its tininess, unique shape, and relative brightness compared to the some of the other Palomars.

Bright Cluster Beats The Glare

Cat's paw? King's crown? Palomar 9's shape depends on your field orientation (north is up here) and what scope you're using. The bright star is Nu2 Sgr.
Anthony Ayiomamitis

* Palomar 10 in Sagitta (R.A. 19h 18m, Dec. +18° 34.3′): Magnitude 13.2, Diameter 4.0′: After trolling the low declinations, how nice to finally tilt the scope into higher, less soupy skies! Good thing, too, because this faint cluster requires inky blackness. I confirmed seeing an exceedingly faint ball of stellar vapor at 142× with averted vision. No stars were resolved.

* Palomar 11 in Aquila (R.A. 19h 45.2m, Dec. –08° 0.5′): Magnitude 9.8, Diameter 10.0′: I assumed the cluster's large size might dash hopes of seeing it, but I was happily proven wrong. 64× showed a faint, round haze at the correct location with quivering granulation visible at 142×. With the scalpel-like precision of high magnification (245×) coupled with averted vision, I could partially resolving the cluster into minute pinpoints.

* Palomar 12 in Capricornus (R.A. 21h 46.6m, Dec. –21° 15′): Magnitude 12.0, Diameter 2.9′: Good lord, this one's small! The upside was that it was more compact than most of the Palomars. I used 245× and saw a 20″ diameter dab of fuzz with a slightly brighter center. Neither granulation nor stars were visible.

A Stunner In Hubble

Palomar 12 really shines in this photo taken by the Hubble Space Telescope.
ESA / NASA / HST

* Palomar 13 in Pegasus (R.A. 23h 06.7m, Dec. +12° 46.3′): Magnitude 13.8, Diameter 0.7′: I suspected but couldn't confirm a small, faint glow at the position using 242× and averted vision.

* Palomar 14 in Hercules (R.A. 16h 11.1m, Dec. +14° 57.5′): Magnitude 14.7, Diameter 2.2′: The faintest of the Palomars. Problematic field stars made this a no-show for me despite 20 minutes of trying. Pal 14 is the most remote globular in our sample — an extreme halo object — located 225,000 light-years from the galactic center and 241,000 from the Sun.

Below you'll find finder charts for several of the brighter Palomar globulars courtesy of Alvin Huey's excellent and free observing guide, Globular Clusters. Click the link and download the .pdf, which includes maps of the remaining clusters and more than 100 others north of –50° declination. The Palomars are also plotted in the Uranometria 2000.0 atlas.

Enjoy these additional resources and photos from other Palomar cluster miners: 1; 2; and 3.

Beat A Path To Palomar 7

Wide- and narrow-field maps showing the location of Palomar 7 (with a few notations on this and subsequent maps by B. King)
Alvin Huey

Beat A Path To Palomar 9

Wide- and narrow-field maps showing the location of Palomar 9.
Alvin Huey

Beat A Path To Palomar 11

Wide- and narrow-field maps showing the location of Palomar 11.
Alvin Huey

Palomar 12 locator

Wide- and narrow-field maps showing the location of Palomar 12.
Alvin Huey

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Bob King

About Bob King

Amateur astronomer since childhood and long-time member of the American Association of Variable Star Observers (AAVSO), Bob King also teaches community education astronomy and writes the blog Astro Bob. The universe invites us on an adventure every single night. All we need do is look up. Check out my forthcoming book "Night Sky with the Naked Eye" (on Amazon and BN) about all the great things you can see at night without any special equipment.

10 thoughts on “Palling Around With Palomar Globular Clusters

  1. SNH

    Alright Bob!
    I’m ready for your challenge!! It’s interesting that the Palomar globular clusters weren’t discovered easily because they reside in the Milky Way. I’ve noticed that because they all ride the ecliptic near the center of the Galaxy. I’m not afraid of a little dimming though! Great article.

    1. Bob KingBob King Post author

      Thanks SNH! Yes, all those Milky Way stars can really get in the way, and of course, the more Milky Way the more dust. I’d love it if you shared your observations of any of these objects here at S&T.

  2. Ernie-OstunoErnie-Ostuno

    I have used a 13.1 inch Odyssey to find all the Palomar Clusters except 1,3,5,10,11,14 and 15. The most difficult were Palomar 4 and Palomar 13, which were similar to the Eridanus globular (google it) in that the brightest few stars were at the threshold of visibility at 333x. One of my favorites is Palomar 2, which was fairly easy in a dark sky. It is along the Fall/Winter Milky Way in Auriga. This also makes Auriga one of the “complete” deep sky constellations with at least one of each type of deep sky object (open and globular clusters, planetary and gaseous nebulae and galaxies).

    The Terzan globulars are also worth trying for in the summer. There are several in the region of Scorpius and Sagittarius, heavily obscured by galactic dust.

    1. Bob KingBob King Post author

      Hi Ernie,
      Nice to hear you saw so many with a 13-inch and good point about Auriga. I’ve tried for some of the Terzans but can’t at the moment recall how many I’ve seen. It would make a nice future article.

      1. Ernie-OstunoErnie-Ostuno

        The problem with the Terzan globulars is not only are they heavily obscured, they are really far south for those of us around 40 degrees North, so their feeble light gets obscured again by the atmosphere. The galactic center needs to be shifted a lot further north!

  3. Bob-PatrickBob-Patrick

    Bob King

    Being a binocular and small refractor observer, I really enjoy you posting the photos and star maps of the Palomar Globular Clusters. Great article.

    1. Bob KingBob King Post author

      Thank you, Bob-Patrick. Nice of you to write. If your refractor is big enough – about 4-inches – I suspect you’d be able to spot Palomar 9.

  4. SNH

    Hey again,
    I just thought I would report my success like you wanted. Out of the ten that you tried, I chose to try seven (Palomar 6, 7, 8, 9, 10, 11, and 12) because of what you reported. And I’m happy to report to you that I believe I saw all seven that I tried – though Palomar 10 was so faint, maybe I should only call it “suspected”! I used only 132x for each one in my 10-inch SCT and want to encourage you to still try for Palomar 6. I know that it’s at a declination of -26°, but I found it to be easier to see than Palomar 7 (-07°) – mainly because it’s smaller and I could see several faint stars over the clusters haze. In fact, I found it to be the third brightest, behind Pal 8 & 9.
    The only Palomar globular clusters I had tried before I read your article were 4, 8, 9, and 13. I was able to glimpse all of them except Palomar 13 with certainty. So thanks for the very good article. It didn’t take me long when I first got interested in astronomy to learn that the most important thing for an adventurous person who only star-hops is maps, plain and simple. That’s really the main reason I hadn’t tried for more Palomar globular clusters before – I didn’t have any excellent maps. So thanks for the link to Alvin Huey’s Globular Clusters PDF. I will continue to use it (I actually used it the same evening to see Terzan 8). It will be especially helpful to me in completing my goal of seeing 100 globular clusters (I’ve already seen about 80, with 50 of those being only with the naked eye and 7×35 binoculars).

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