IC 4756
Scientific overview
IC 4756 is an open cluster in the constellation Serpens. It shines at apparent magnitude 4.6 and spans about 24 arcminutes of sky.
Observation guide
Guidance follows standard observing practice, derived from the object's real magnitude and position. A dark, moonless sky always helps.
Location in the sky
Precision measurements
Distances and velocities from SIMBAD · IC 4756
| Distance | 1,545 ly | SIMBAD · catalogued |
| Physical size (major axis) | 10.786154 ly | SIMBAD · derived |
| Radial velocity | -24.91 ± 0.09 km/s | SIMBAD · measured |
| Right ascension (ICRS) | 279.649167 deg | SIMBAD · measured |
| Declination (ICRS) | 5.435 deg | SIMBAD · measured |
Full field-level provenance
- Distance: Centre de données astronomiques de Strasbourg (CDS) · SIMBAD · mesDistance · dist · 2022ApJ...931..156P · catalogued value · source value 473.7 pc · retrieved 2026-07-11
- Physical size (major axis): Centre de données astronomiques de Strasbourg (CDS) · derived (OpenNGC angular size × SIMBAD distance) · physical size = angular size × distance (small-angle); angular size from OpenNGC, distance from SIMBAD mesDistance · derived · retrieved 2026-07-11
- Radial velocity: Centre de données astronomiques de Strasbourg (CDS) · SIMBAD · basic · rvz_radvel · 2021A&A...647A..19T · direct catalogue measurement · retrieved 2026-07-11
- Right ascension (ICRS): Centre de données astronomiques de Strasbourg (CDS) · SIMBAD · basic · ra · 2021A&A...647A..19T · direct catalogue measurement · retrieved 2026-07-11
- Declination (ICRS): Centre de données astronomiques de Strasbourg (CDS) · SIMBAD · basic · dec · 2021A&A...647A..19T · direct catalogue measurement · retrieved 2026-07-11
Physical size is derived from the OpenNGC angular size and the catalogued distance (small-angle: size = angle × distance). This is a Galactic object: its Doppler shift is shown as a radial velocity, not a cosmological redshift. Fields a source did not provide are omitted, never invented.
Other objects in Serpens
| Object | Type | Mag | Size (′) |
|---|---|---|---|
| M 5M 5 · NGC 5904 | Globular cluster | 5.95 | 15 |
| Eagle Nebula | Nebula | 6 | 5.05 |
| Eagle NebulaM 16 · NGC 6611 | Nebula | 6 | 120 |
| NGC 6605NGC 6605 | Open cluster | 6 | 6.3 |
| NGC 6604NGC 6604 | Open cluster | 6.5 | 9.6 |
| NGC 6535NGC 6535 | Globular cluster | 9.85 | 3.6 |
Sources
The primary and reference sources this topic draws on.
- OpenNGCOpenNGC (M. Verga) — NGC/IC, Messier, and Caldwell catalogue data
Openly-licensed deep-sky catalogue: object types, positions, magnitudes, sizes, morphology, and cross-identifiers.