When is the best time to observe Caldwell 10?

Caldwell 10 is best observed from September through November, with peak visibility during October when it transits around midnight in the Northern Hemisphere.

Where is Caldwell 10 located in the sky?

Caldwell 10 lies in the constellation Cassiopeia at right ascension 01h 46m and declination +61° 13′.

What telescope do I need to see Caldwell 10?

At magnitude 7.1, Caldwell 10 is easy in 7×50 or 10×50 binoculars.

Caldwell 10 — Open Cluster in Cassiopeia

NGC 663

Open Cluster Excellent (73/100)

Magnitude 7.1^m OpenCluster Cassiopeia Visible

Credit: Hewholooks. License: CC BY-SA 3.0. (Wikimedia Commons)

Star Map + List + Plan Star Hop

About C10

Description

NGC 663 is a bright, rich open cluster in Cassiopeia, about 6,850 light-years away. It contains over 400 stars spread across 16 arcminutes, with many hot blue B-type stars and several red supergiants.

Observing Tips

An easy and rewarding target, visible in binoculars as a hazy patch and stunning in small telescopes. A 4-inch scope at 50-80x reveals dozens of stars. Circumpolar from northern latitudes, best placed in autumn.

History

Discovered in 1654 by Giovanni Battista Hodierna. Independently found by William Herschel in 1787. One of the finest open clusters in Cassiopeia.

Fun Facts

NGC 663 is only about 20-25 million years old. It contains an unusual number of Be stars — rapidly rotating hot stars with circumstellar disks — making it ideal for studying this phenomenon.

Observe

1Properties

Magnitude 7.1

Angular Size 6.0′

Distance 6,800 ly

Description

Open Cluster [Distance: 6800 ly]

Position & Identifiers

RA 01h 46m 16.1s

Dec +61° 13' 04.8"

Constellation Cassiopeia

Catalog C10

Also known as NGC 663

Physical size

17 light-years across — about 2.0× the Sun-to-Sirius distance

2How easy to spot?

Telescope	Bortle 3	Bortle 4	Bortle 5
80 mm refractor 80mm refr.	Easy	Easy	Easy
150 mm Newton 150mm Newt.	Easy	Easy	Easy
Celestron C8 (203 mm SCT) 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 87 of 468 members.

3Visibility

Set a location in User Settings to see visibility data.

Best season Sep – Nov (peak: Oct)

4 Eyepiece View

Telescope Eyepiece

125x TFOV: 0.4° Lim. mag: 13.6

C10 · 6.0′ diameter

5 Best Magnification

6Where this cluster sits in time

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.