Object of the Week December 13, 2015 – NGC 288

Object of the Week December 13, 2015 – NGC 288

NGC 288, Cl Melotte 3, GCl 2, Bennett 5

Constellation: Sculptor
Type: Globular Cluster, Class X
RA: 00h 52m 45s
Dec: -26° 34’ 57”
Distance: 37,000 ly
Size: 13.0’
Mag: 8.1


This week’s OOTW is the unusual and obscure globular cluster, NGC 288.

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Although it is moderately bright and large, it is located in a constellation relatively unknown to many Northern Hemisphere observers – Sculptor. Often the one and only deep sky attraction in Sculptor for many observers is the oblique spiral galaxy NGC 253, aka the Sculptor Galaxy. NGC 288 is located 1.8° southeast of the Sculptor Galaxy. In a 3° field of view NGC 288 rises from obscurity and shares the spotlight with NGC 253. Stephen O’Meara in Deep-Sky Companions: Hidden Treasures opines that “Few sights in the sky are as rewarding as seeing this dramatic pairing of deep-sky splendors.”

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At a declination of -26° NGC 288 may seem to be off limits to observers in the mid and northern latitudes – however it is not. In fact, this cluster was discovered from a rather northerly latitude of 51° by William Herschel in October 1785. Although NGC 288 culminates at the meridian in mid-October, early sunsets in the Winter provide an ample window of opportunity to observe at dusk, at least for a few more weeks. An absolute key to a successful observation is access to an unobstructed southern horizon.

William Herschel’s discovery notes for the cluster he logged as H VI-20 describe it as “Considerably bright, irregularly round, 8’ or 9’ in diameter. A great many of the stars are visible so there can remain no doubt that it is a cluster of very small stars.”

Unfortunately I have yet to log an observation of NGC 288, so instead I must rely on the DSF membership to share their observations and sketches, as they regularly do. Meanwhile I’ll share a few observational characteristics I garnered from The Night Sky Observer’s Guide, Volume 1 by George Kepple and Glen Sanner.

• [the cluster] is partially enclosed by a semicircular star chain open on the SW side
• the large dense core is embedded in a much less concentrated halo 7’ in diameter and irregular in outline
• outlying members spread noticeably further to the south and SW
• the loosely-structured Class X globular has a 9’ diameter but a star-poor halo around a dense 3’ diameter core
• the globular’s periphery is irregular in profile

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Hubble ACS image

What makes NGC 288 such an unusual globular cluster?

• the cluster travels in an oddball retrograde orbit
• it is a loose halo cluster whose members each contain, on average, anywhere from 1/13 to 1/20 as much iron as the Sun
• based on the large number of massive bright blue stars that have left the red giant phase and are being powered by helium fusion (on the so-called Horizontal Branch) – the age of NGC 288 has been calculated to be 13 to 14 billion years old, which places it among the very oldest globular clusters

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Now it’s your turn….don’t forget to share your observations and sketches of this incredible globular cluster.

As always,

"Give it a go and let us know!
Good luck and great viewing!"

Hi Mark,

Interesting object and great story! I observed this globular cluster with my 6" telescope from southern France though my notes are quite sparse. The cluster already was visible in my finder. At 170x I could barely see the cluster but I did see some stars resolved in it. Looks like I need to revisit it.


Clear skies, Wouter

This is nice cluster typically seen on the way to NGC 253. I first saw it when doing the Herschel 400 with my short-focus 4". We are at 42N here.

Very nice duo together with NGC 253 as you mentioned

20x125 binocular, NELM 6m+, field 3°
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I had a nice look at NGC 253 in October with the 28 inch, and while in the area had a look at NGC 288 - I usually look at both but it's always 253 that brings me to the neighborhood. No notes or sketches of 288 this time but I remember it being well resolved and quite a nice globular. I do have a description from 2004 with an 80mm refractor though:

"Surprisingly easy to see with the 31mm Nagler together as they comfortably fit into the field of view. 253 was an elongated glow with three field stars, and 288 was a round and somewhat fainter glow. Up to 80x I could see no resolution of 288."

My last observation of NGC 288 was on the 7th of November, last month with my Tak FC76DC. I confess that I have never spent time on this globular separately as I consider it a "sidekick" of NGC 253. It is easy pickings in any class of instrument and my log states that it was easily visible through my 50mm finderscope. Time for another visit but this time paying more attention :D

My last observation was in October using the 30-inch at the OzSky "star party" (just 3 U.S. participants) under SQM 21.8-22.0 skies. I always visit NGC 288 whenever I view NGC 253, so these are just a sampling in different scopes:

30" (10/15/15 - OzSky): this very loose globular appears fully resolved at 303x. There were too many stars to possibly count, but certainly several hundred were resolved including a number of relatively bright stars (brightest members mag 12.6). The core is loosely overlaid with a dozen or so brighter stars. A number of stars in the halo appear to be arranged in strings and arcs including one string extending towards the west.

18" (1/1/08): at 220x-280x, ~60 stars were resolved in an 8' diameter. This globular has a very loose, irregular appearance with a very small brighter core containing a clump of resolved stars. A string of stars running SSW-NNE runs through the west side of the halo with a brighter star (double) at the NNE end of this string. A roughly parallel string also passes through the east side of the halo. Located 1.8° SE of NGC 253 and forms a nice pair in the 80mm finder at 13x.

18" (8/25/06): this bright globular is quite loose (concentration class 10) and well-resolved at 220x over the entire face and halo. The outer halo is very irregular with a scraggly appearance and extends to 8'-10' in diameter. Roughly 100 stars were resolved in total.

17.5" (8/29/92): very bright, very large, round, ~8' diameter. Well-resolved over entire disc into 75-100 stars mag 13-15 over background glow, although not densely packed. Observation from the White Mountains (12,500 ft elevation).

13.1" (11/5/83): 30-40 stars resolved over haze.

8" (10/13/81): faint stars resolved across entire disc at 200x with averted, many near visual limit.

15x50mm (8/25/06): easily visible in IS binoculars as a fairly large, diffuse glow.