IC 1257 (OCL-51, C 1724-070) Globular Cluster in Ophiuchus

Located at: RA 17 hours 27 minutes 08 seconds, Dec -07 degrees 05 minutes 36 seconds

Size: 5.0.'* Magnitude: 13.1 Class: --

North is up

West to the right

Telescope:

 14.5" f5 Newtonian reflector

Camera:

 ST-8XME, self-guided, binned 1x1, temp -15c, camera control MaxIm DL 4.56

Image:

Lumicon Red filter, 600 minutes (60 x 10 minute subs), 07/16/17/18/19/2017; seeing 2.3-4.1 FWHM per CCDStack

Processing: CCDStack 2.94.6355.18107, Photoshop CS5.1
Location:

 Rolling Roof Observatory, Thousand Oaks, CA 91360 (+34d 13m 29s -118h 52m 20s)

Notes:*

Imaged this last (for this month) southern object before moving to the east to avoid the coming moon ... This globular is listed in Megastar (v5.0.14) as 5.0 minutes in diameter, but looks to be barely 2.0' on my image. See this entry for IC 1257 from the "A galactic globular clusters database".

From the NGC / IC Project:

Steve's Notes

IC 1257 = OCL-51 = Lund 751 = Ced 144

17 27 08.5 -07 05 35

V = 13.1;  Size 1'

18" (7/26/06): picked up at 225x, but viewed at 325x as a very faint, low surface brightness disc of 30" diameter with only a very weak central brightening.  This challenging globular was visible steadily, even with direct vision but there was no hints of details.  A couple of mag 16-16.5 threshold stars are close south and west.

18" (7/18/04): at 250x, appeared very faint, very small, round, ~0.5' diameter.  With direct vision, this globular is weakly concentrated to a faint quasi-stellar or stellar core.  Visible continuously without much effort, though very unimpressive as a globular.

17.5" (6/30/00): at 280x this small low surface brightness globular appeared very faint, round, ~30" diameter but visible with direct vision.  Appears to have an extremely faint knot at the south edge and a slight central brightening.

17.5" (7/27/95): very faint, round patch, ~1' diameter.  Appears similar to a 15th magnitude galaxy with no hints of resolution or central concentration.  Can hold steadily with averted vision.  Located 5.8' W of a mag 11.5 star.  Discovered to be a globular in 1996.

13.1": not found.

Rudolph Spitaler discovered IC 1257 on 7 July 1890 while searching for Barnard's Comet C/1888 RI using the 27" refractor at Wien University Observatory in Austria.  His micrometric position is accurate.  Barnard himself, also discovered it the next night, while searching for the same comet with the 12-inch refractor at Lick Observatory.  Barnard initially mistook it for the comet!

Harlow Shapley listed IC 1257 as an open cluster (1930) and Sven Cederblad as a nebula (1946).  Brian Skiff reports in 9/96: Barry Madore to take a handful of short exposures of it at the Palomar 200", and has run through a first-cut data reduction.  The color-magnitude diagram shows that it is unquestionably a globular cluster, which is moderately heavily reddened:  it has the telltale marks of a metal-poor halo cluster, which are (a) a blue horizontal-branch population and (b) a steep red-giant branch.  See Harris et al. http://adsabs.harvard.edu/abs/1997AJ....113..688H for the discovery announcement.