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NGC 6866 — Open Cluster in Cygnus

Open Cluster Good (51/100)
Magnitude 7.6m OpenCluster Cygnus (Cyg) Visible
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1Properties

Magnitude 7.6
Angular Size 5.1′
Cl, L, vRi, cC

Position & Identifiers

RA 20h 03m 55.2s
Dec +44° 09' 32.8"
Constellation Cygnus (Cyg)
Catalog NGC 6866
Physical size
6.8 light-years across — about 1.6× the Sun-to-Alpha-Centauri distance

2How easy to spot?

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Telescope Bortle 3 Bortle 4 Bortle 5
80mm refr. Easy Easy Easy
150mm Newt. Easy Easy Easy
C8 203mm Easy Easy Easy
Easy Medium Hard Very hard Impossible

Bortle 3 = rural · 4 = outer suburbs · 5 = suburbs

Easy on Seestar S50
At 150mm under B5 skies you should resolve about 25 of 72 members.

3Visibility

Set a location in User Settings to see visibility data.

Best season Jun – Aug (peak: Jul)

4 Eyepiece View

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125x TFOV: 0.4° Lim. mag: 13.6
N E

NGC 6866 · 5.1′ diameter

5 Best Magnification

6Where this cluster sits in time

1 Myr 10 Myr 100 Myr 1 Gyr 10 Gyr NGC 2362 Pleiades M67 NGC 188 NGC 6866 646 Myr

Open clusters span more than four orders of magnitude in age — from newborn OB associations to ancient, metal-rich survivors.

7 Colour-Magnitude Diagram

A cluster's colour-magnitude diagram reveals its age: the bluer the turn-off point where the main sequence bends into red giants, the younger the cluster.

Loading member data…

Each point is a Gaia-DR3 member. Colour encodes spectral type; size reflects membership probability.

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8 Classification Decoder

Nearby in the Sky

Other targets within a few degrees — pan your scope a little and keep exploring.

Visibility scores assume a 150 mm Newton at Bortle 4.

31 Cyg
Easy
Colorful double, sep 336.7″
Double Star mag 3.79 3.1° Cygnus
Collinder 421
Easy
Open cluster
Open Cluster mag 10.1 4.3° Cygnus
Collinder 419
Easy
Open cluster
Open Cluster mag 5.4 4.3° Cygnus
NGC 6910
Easy
Open cluster
Open Cluster mag 7.4 4.9° Cygnus
V973 Cyg
Medium
Semi-regular variable, range 6.1–6.8
Variable Star mag 6.34 4.9° Cygnus
NGC 6811
Easy
Rich open cluster
Open Cluster mag 6.8 5.1° Cygnus
Crescent nebula
NGC 6888
Medium+
Emission nebula — try an OIII filter
Emission Nebula mag 7.44 6.0° Cygnus
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