Open Cluster NGC 2506

NGC 2506
NGC 2506: Section from DSS2 [147]


This open cluster was discovered by William Herschel on 23 February 1791. He logged it as VI 37 and recorded: «A very compressed and very rich cluster of stars. The stars ar of 2 sizes, some considerably large and the rest next to invisible. The compressed part 5 or 6' in diameter.» [465] John Herschel logged the cluster on 9 March 1828 as h 480 and wrote: «The first star 11m in the preceding part of a rich round pretty compressed cluster of irregular figure. Stars 11...20m, so as to be nebulous. The most compressed part = 4' or 5' diameter.» [466]

Lord Rosse, or one of his observing assistants have visited the cluster frequently and noted: «Several observers have fancied that the stars exhibit some approach to a spiral arrangement, with cellular center. No unresolved nebulosity.» [486]

Physical Properties

NGC 2506 is an intermediate-age (2.01 ±0.10 Gyr) open cluster. 2175 cluster members have been identified based on Gaia EDR3 data. Distance has been derieved to 3.101 ± 0.017 kpc. [190, 209]

Revised+Historic NGC/IC Version 22/9, © 2022 Dr. Wolfgang Steinicke [277]
Designation NGC 2506
Type OCL (I2r)
Right Ascension (J2000.0) 08h 00m 01.7s
Declination (J2000.0) -10° 46' 11"
Diameter 12 arcmin
Visual magnitude 7.6 mag
Metric Distance 3.460 kpc
Dreyer Description Cl, pL, vRi, C, st 11…20
Identification, Remarks WH VI 37; h 480; GC 1611; OCL 593

Finder Chart

The open cluster NGC 2506 is located in the constellation Monoceros. The best season for observation is from October until March.

Finder Chart Open Cluster NGC 2506
Open Cluster NGC 2506 in constellation Monoceros. Charts created using SkySafari 6 Pro and STScI Digitized Sky Survey. Limiting magnitudes: Constellation chart ~6.5 mag, DSS2 close-ups ~20 mag. [149, 160]

Objects Within a Radius of 15°


  • [147] Aladin Lite;
  • [149] SkySafari 6 Pro, Simulation Curriculum;
  • [160] The STScI Digitized Sky Survey;
  • [190] «UV study of the open cluster NGC 2506 using ASTROSAT» Anju Panthi, Kaushar Vaidya, Vikrant Jadhav, Khushboo K Rao, Annapurni Subramaniam, Manan Agarwal, Sindhu Pandey; Monthly Notices of the Royal Astronomical Society, Volume 516, Issue 4, November 2022, Pages 5318–5330; DOI:10.1093/mnras/stac2421
  • [209] «Extremely precise age and metallicity of the open cluster NGC 2506 using detached eclipsing binaries» E Knudstrup, F Grundahl, K Brogaard, D Slumstrup, J A Orosz, E L Sandquist, J Jessen-Hansen, M N Lund, T Arentoft, R Tronsgaard, D Yong, S Frandsen, H Bruntt Monthly Notices of the Royal Astronomical Society, Volume 499, Issue 1, November 2020, Pages 1312–1339; DOI:10.1093/mnras/staa2855
  • [277] «Historische Deep-Sky Kataloge» von Dr. Wolfgang Steinicke; (2021-02-17)
  • [465] «Catalogue of 500 new nebulae, nebulous stars, planetary nebula:, and clusters of stars; with remarks on the construction of the heavens» William Herschel, Philosophical Transactions of the Royal Society of London, 1 January 1802; DOI:10.1098/rstl.1802.0021
  • [466] «Observations of nebulæ and clusters of stars, made at Slough, with a twenty-feet reflector, between the years 1825 and 1833» John Frederick William Herschel, Philosophical Transactions of the Royal Society of London, 1 January 1833, Pages: 359-505; DOI:10.1098/rstl.1833.0021
  • [486] «On the construction of specula of six-feet aperture; and a selection from the observations of nebulæ made with them» William Parsons; Philosophical Transactions of the Royal Society of London, Volume 151, published 1 January 1861; DOI:10.1098/rstl.1861.0029