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Cosmic Challenge: Palomar 2

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Cosmic Challenge: Palomar 2


February 2023

Phil Harrington

This month's suggested aperture range:

15-inch (38-cm) telescopes and up












Palomar 2


04h 46.1m

+31° 22.9'





When it was released more than half a century ago, the Palomar Observatory Sky Survey showed the universe at a level of detail never before achieved.  This major photographic survey covers the sky from the north celestial pole to -30° declination and recorded stars down to an average of magnitude 22.


Astronomers at the time immediately turned to the Survey's 900-plus photographic plates to examine known objects in exquisite detail as well as to discover other sights that earlier studies had missed.  For instance, 86 planetary nebulae were discovered on the plates by American astronomer George O. Abell. (Footnote: Two of Abell's planetaries were already in the NGC catalog (Abell 50=NGC 6742 and Abell 75=NGC 7076), while another pair were already in the IC catalog (Abell 37=IC 972 and Abell 81=IC 1454.)


During a survey of the Survey, Abell, along with Halton Arp, Walter Baade, Edwin Hubble, Fritz Zwicky, A.G. Wilson, and others, cataloged 15 "unknown" Milky Way globulars. As with four of the planetary nebulae, two Palomar globulars -- Palomar 7 and Palomar 9 -- were previously known. The former is listed as IC 1276, while the latter is NGC 6717. But regardless, each represents a suitably daunting test for today's most diehard deep-sky observers. 


Palomar 2, discovered by A.G. Wilson in 1955, is a particularly nasty cluster to spot because it is partially concealed behind a dark nebula in Auriga.  Barnard 221 spans ¾° and is centered just 32' northwest of Palomar 2.  The dark nebula may not be readily evident by eye, but it has a stifling influence on Palomar 2.


Above: Evening star map showing the location of this month's Cosmic Challenge.


Credit: Map adapted from Star Watch by Phil Harrington


Above: Finder chart for this month's Cosmic Challenge.


Credit: Chart adapted from Cosmic Challenge by Phil Harrington
Click on the chart to open a printable PDF version in a new window



Most globular clusters associated with the Milky Way are positioned around the galactic nucleus, and so are referred to as "inner-halo globulars."  There is a second family, however, whose members lie far beyond the Galaxy's center and so are known as "outer-halo globulars."  Of all the outer-halo globulars known, Palomar 2 is the most extreme, located almost directly opposite the Galactic center in Sagittarius, separated by 85,400 light years.  A 1997 analysis entitled Unveiling Palomar 2: The Most Obscure Globular Cluster in the Outer Halo conducted by Professor William E. Harris and colleagues from McMaster University in Hamilton, Ontario, found that Palomar 2 is it is one of the brightest and most massive clusters in the outer halo.


That distinction goes completely unappreciated through our telescopes, however, because Palomar 2 is also one of the most heavily obscured.  As a result, we see only a vague inkling of the cluster's true self.  In many images, the dark nebula's presence also reddens the stars' hues.


To find it, scan 2° southwest of Iota (ι) Aurigae, the southwestern star in the Auriga pentagon.  Keep an eye out for a triangle of three 6th- to 7th-magnitude stars.  The brightest and westernmost star in the triangle, SAO 57441, is 40' due east of the cluster.  A close-set pair of 12th- and 13th-magnitude stars lying halfway between the two makes a useful checkpoint along the way.  Another close stellar duo, shining faintly at magnitudes 13 and 14.5, is just 2.3' northeast of the cluster.

Above: Palomar 2 through the author's 18-inch (46-cm) reflector.


Below: The view of Palomar 2 as captured by the Hubble Space Telescope.

Credit: ESA/Hubble & NASA


For most readers, see Palomar 2 will take the firepower of at least a 15-inch (38-cm) scope to pull out its tiny glow from the surroundings.  Palomar 2 has a listed magnitude of 13, and so may be visible through smaller telescopes if attempted under very dark skies.  Through my 18-inch (46-cm) reflector under suburban skies, it is an extremely dim, but doable, smudge measuring no more than 1' across, as shown in the rendering above.  Averted vision is a must no matter which eyepiece I use, although I have found the best view was at 171x.  The overall impression is more reminiscent of a distant galaxy than a globular cluster.  Indeed, it was this vague appearance that led Boris Vorontsov-Velyaminov and V. P. Arkhipova to misclassify Palomar 2 as a galaxy in their Morphological Catalog of Galaxies (MGC) compiled by in the 1960s.  Even today some references cross-list Palomar 2 as MCG +05-12-1.


Have a favorite challenge object of your own?  I'd love to hear about it, as well as how you did with this month's challenge.  Contact me through my website or post to this month's discussion forum.


Remember that half of the fun is the thrill of the chase.  Game on!

About the Author:

Phil Harrington writes the monthly Binocular Universe column in Astronomy magazine and is the author of 9 books on astronomy.  Visit his web site at www.philharrington.net to learn more.

Phil Harrington's Cosmic Challenge is copyright 2023 by Philip S. Harrington.  All rights reserved.  No reproduction, in whole or in part, beyond single copies for use by an individual, is permitted without written permission of the copyright holder.


  • okiestarman56, John O'Hara, StarAlert and 1 other like this


Here's an observation with my 18-inch Starmaster:


Palomar 2 was immediately picked up at 285x as a faint, fairly small, roundish glow, ~1.5' diameter.  Easily visible with averted vision and it could be held continuously without difficulty.  The cluster is very weakly concentrated with a very small brighter core or knot that seemed offset from the geometric center.  Pal 2 is partially obscured by the dark cloud Barnard 221, which lies to the northwest.



    • Dave Mitsky, PhilH and John O'Hara like this

Excellent one

    • PhilH likes this

I saw this globular on Nov 23, 2019 at our club's dark sky site near Kerrville, TX. I used my Obsession 25" F5 with a ParaCorr and 3 different Explore Scientific eyepieces. Here is what I wrote:


Very faint and small: ~75" across, circular. Located 2' west of a faint pair of stars oriented n-s separated by 30". I could hold it with direct vision. Averted vision shows a slightly brighter center. Very little concentration. Poorly defined. SS class X or XI. So little detail it is hard to say - call it X. Unresolved: perhaps only one star seen at the cluster center. 261x (14 mm) was best. 183x (20 mm) was OK. 406x (9 mm) was poor.


Dave Wickholm

    • PhilH and John O'Hara like this

Here are my EAA of Palomar 2.  Very interesting.




Camera: Nikon D5100

Scope - Astro-Tech AT125EDL

Mount: Sky Watcher EQ6-R Pro

OS: Stellarmate on Raspberry Pi 4


One is a wide field of view to appreciate the size of Palomar 2.  The other is a cropped image.  Both were stacked with Deep Sky Stacker and only color leveled with Gimp.


palomar 2 DSS leveled
Album: Palomar 2
2 images

    • PhilH likes this

I was able to detect Palomar 2 as a faint glow. I was using my 16 inch with a Paracorr 2 and Type 6 Naglers. We were camped NE of Desert Center, Skies measured 21.6 mpsas.  I verified it with a DSS image..


For my old eyes, it was at the limit..



    • PhilH and John O'Hara like this

Guy who lives in suburbs with kids and didn't have time to get to a dark site to see M2 resorts to camera (and borrows Hubble data):




It was a fun project, for me also part of the AL's glob list.  The Palomars are great goals.





    • PhilH likes this

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