Galactic Open Clusters Reference Catalog
Astrometric and isochrone reference index of young Galactic disk star clusters calibrating the base of the cosmic distance ladder.
Catalog Scope & Cross-Identification Notes
Nearby open star clusters in the Galactic disk share common space velocities, ages, and initial chemical compositions, allowing astronomers to fit stellar evolution isochrones across main-sequence turnoffs from 14 Myr (Double Cluster) to 650 Myr (Hyades and Beehive).
This catalog connects classical Messier, NGC, and Melotte designations with high-precision Gaia DR3 trigonometric parallax distances and Trumpler richness classes.
Cross-Referenced Objects in Galactic Open Clusters Reference Catalog (4)
| Object Profile | Primary Class | Constellation | RA (J2000) | Dec (J2000) | Catalog Aliases | Best Season |
|---|---|---|---|---|---|---|
| Hyades (Melotte 25 Nearest Cluster) | Open star cluster (nearest open cluster to the Sun) | Taurus | 04h 26m 54.00s | +15° 52′ 00.0″ | Melotte 25, Collinder 50, Caldwell 41 | Late Autumn to Winter (November–February) |
| Pleiades (Messier 45 Open Cluster) | Open star cluster with dusty reflection nebulosity | Taurus | 03h 47m 00.00s | +24° 07′ 00.0″ | M45, Seven Sisters, Melotte 22 | Late Autumn to Winter (November–February) |
| Beehive Cluster (Messier 44 Praesepe) | Open star cluster | Cancer | 08h 40m 24.00s | +19° 40′ 00.0″ | M44, Praesepe, NGC 2632 | Late Winter to Spring (February–May) |
| Double Cluster (NGC 869 & NGC 884) | Twin young supergiant open clusters (Perseus OB1 core) | Perseus | 02h 20m 00.00s | +57° 08′ 00.0″ | NGC 869, NGC 884, h and Chi Persei | Autumn to Winter (September–January) |
Related Reference Guides
Trigonometric Parallax, Parsecs & Gaia DR3
How trigonometric parallax (d_pc = 1 / p_arcsec), the distance modulus equation, Hipparcos, and Gaia DR3 microarcsecond astrometry measure cosmic distances.
Stellar Spectral Classification (OBAFGKM)
Reference guide to Morgan-Keenan (MK) stellar classification (O B A F G K M), luminosity classes (I–V, WD), color index (B-V), and the H-R diagram.
Angular Size, Separation & Field of View
How angular diameter (degrees, arcminutes, arcseconds), spherical angular separation, and small-angle physical diameter relate to telescope field of view.
Primary Catalog Sources
- ESA Gaia Archive — Data Release 3 (DR3 (2022-06-13)): Gaia Collaboration, Vallenari, A., et al. 2023, A&A, 674, A1 (Gaia Data Release 3) — European Space Agency / Gaia DPAC
- Revised New General Catalogue and Index Catalogue (RNGC/IC) (2024/2026 edition): Steinicke, W. 2010, Observing and Cataloguing Nebulae and Star Clusters (Cambridge Univ. Press); Verga, M. OpenNGC (CC-BY-SA 4.0 / data tables) — Wolfgang Steinicke / OpenNGC
- SIMBAD Astronomical Database (CDS) (2026-10 release): Wenger, M., et al. 2000, A&AS, 143, 9 (The SIMBAD astronomical database) — Centre de Données astronomiques de Strasbourg