Object of the Week, June 24, 2018 – Palomar 8

[Steve Gottlieb]

Palomar 8
Aliases: ESO 591-012 = C 1838-198
Type: Globular Cluster
Class: X

RA: 18h 41m 29.9s
Dec: -19° 49' 33"
Constellation: Sgr

Size: 4.7'
Mag: 11.2V
Brightest Star: 15.4V
Distance (Galactic center): 18000 l.y.
Distance (sun): 42000 l.y.

PanSTARRS image:
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Palomar 8 is well known as one the brightest of the 15 globular clusters found on the Palomar Observatory Sky Survey in 1950's. In the case of Pal 8, it was George Abell who made the discovery, who was one of the principal "observers", taking and examining plates on the sky survey. Two of the Palomar globulars turned out to be previously discovered visually -- Palomar 9 = NGC 6717 and Palomar 7 = IC 1276.

Palomar 8 is quite impressive through an 18-inch scope, but you certainly don't need a larger aperture to view this globular. Brian Skiff reported it visible in a 70mm Pronto at 55x and Les Dalrymple reported it as faintly visible in 15x80 binoculars from Australia.

Here are my notes through my 18-inch Starmaster --
225x: "Palomar 8 is moderately bright, round, ~3' diameter, with little or no central concentration. Four or five faint stars are scattered around the periphery."
434x: "The surface brightness is very irregular and mottled and the halo is no longer round but more ragged. A nice mag 14 double star is at the south edge and a couple of additional fainter stars scintillate in and out of visibility over the disc."

In a separate observation with my 18-inch I recorded "a dozen very faint stars resolved over the face of the cluster".

Palomar 8 is brighter and more evident visually than several of the NGC globulars, so the question remains is why wasn't it picked up visually by the Herschels in their sky surveys (John picked up NGC 6380, for example, as well as NGC 6749)?

It turns out E.E. Barnard discovered Palomar 8 visually on 3 July 1889 using the 12-inch refractor at Lick Observatory!

While carefully reading through his observing logs I was surprised to find it included Palomar 8, though he failed to report the discovery. He called it "small, round, gbM, 2' or 3', p[receding] 9 1/2 mag or 10m star. With 700x probably resolvable. It is likely a globular cluster. I can occasionally see the stars. Much compressed, 13 mag… With lower powers, looks like a small faint comet or nebula."

There you go. Not only did Barnard discover this object with a 12", he realized it was likely a globular and partially resolved it!

Now you give it a go and let us know!

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[wvreeven]

Great pick and to my surprise I observed it with my 20" telescope on September 24, 2011, which is two months after I moved from the Netherlands to Spain. Back then I was using a 35 mm Panoptic eye piece and 16 mm, 7 mm and 4 mm SkyWatcher UWAN eye pieces (as compared to a 31 mm Nagler and all but the 13 mm Ethos ones today). My notes read

"Both with the 35 mm and the 16 mm an easy target. Using the 16 mm several stars in the cluster were resolved and there is an m=11 star at one edge."

I guess that star must be TYC 6288-02014-1.

[Jimi Lowrey]

Great choice Steve it is amazing that Professor Barnard did not report the discovery of pal 8. Good job by you to find it in his logs. Having seen his logs it is amazing to me you can read his writing!!!!

[Ivan Maly]

With Pluto marked in the field, in 2013:

http://1.bp.blogspot.com/-1Gxz_P7VMMs/Ue2ZZI6GG1I/AAAAAAAAAg0/ceYdbkhXzBU/s1600/2013-07-16+Pluto+and+Pal+8.jpg

[KidOrion]

My notes from 7/28/14 (SEEING: 7, 5 at horizon—improved to 8 around midnight; TRANSPARENCY: 8 [horizons 6]; NELM: 6.3)


12:06
Palomar 8 (Sgr) —starhopped to, found w/direct vision—in crowded field—diffuse glow; 12th mag?—fairly loose concentration—to S edge, embedded just in halo, a faint (13th-mag) star—off to F edge is another of similar brightness—easily visible cluster—holdable w/direct—brighter than some NGCs—many faint field stars around cluster—3.5’-4’?—impossible to tell CC—w/averted almost wants to seem on edge of being granular, esp. on P side—quite large glob—looks like F-side star may be v. close pair—brightest star in field to SF by 12’, 8-9 mag—in 6mm Radian star to F side is double/pair

[Howard B]

That's a really cool double observation Ivan!

[Bertrand Laville]

Hi All,

Here is my observation and drawing from Tivoli lodge, Namibia, with a 20*" Obsession.
Very good sky*: NELM 7,64 at h 45°, SQM 21,87, seeing medium.

98x, Nagler 26mm*: hazy patch, easy, mottled, more or less round, D ~ 2'.
231x Nagler 11mm*: the patch looks as a 3D image, the mottled appearance increases. Gradient is weak.
726x Nagler 3,5mm*: not allways resolved, but two dozen of faint stars appear on the patch, most of them on the west side.
Palomar 8 is an easy target among the Palomar globulars.


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Detailed report here: http://www.deepsky-drawings.com/palomar-8/dsdlang/en
By the way, all other Palomar reports at: http://www.deepsky-drawings.com/category/catalogue/b-catalogues-specific/b1-groupes-etoiles/1-palomar/dsdlang/en

Clear sky
Bertrand
http://www.deepsky-drawings.com/dsdlang/en/

[Uwe Glahn]

Impressive notice that Barnard discovered Pal 8. But indeed, the entries in his observer's logbook reads fantastic.

My entries from 4" to 27", all from ~48°N latitude are as follows:
4", 88x, NELM 6m5+
at 18x not visible; with 44x easy but small; best view with 88x; rich star field; no concentration to its middle; 2 faint stars at the border; can hold GC with direct vision
12", 190x, NELM 6m5+
bright and easy to detect; mottled appearance with 3-4 stars glimpsed trough the GC; a little bit concentrated to the middle; 3 brighter foreground stars around GC
15", 285x, NELM 7m+
bright with mottled appearance
16", 257x, NELM 7m+
rich star field, GC easy to detect, mottled appearance, a few very faint stars glimpsed trough the GC, faint stars around the globular star cluster
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27", 113x-419x, fst 7m0+
bright; 12mag double star at the NW edge; GC looks granular; one dozen stars could be resolved; star clump W of the middle; not concentrated