When is the best time to observe NGC 129?

NGC 129 is best observed from August through October, with peak visibility during September when it transits around midnight in the Northern Hemisphere.

Where is NGC 129 located in the sky?

NGC 129 lies in the constellation Cassiopeia at right ascension 00h 30m and declination +60° 13′.

What telescope do I need to see NGC 129?

At magnitude 6.5, NGC 129 is easy in 7×50 or 10×50 binoculars.

NGC 129 — Open Cluster in Cassiopeia

Open Cluster Excellent (65/100)

Magnitude 6.5^m OpenCluster Cassiopeia (Cas) Visible

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1Properties

Magnitude 6.5

Angular Size 5.4′

Description

Cl, vL, pR, lC, st 9...13

Position & Identifiers

RA 00h 29m 58.2s

Dec +60° 12' 40.3"

Constellation Cassiopeia (Cas)

Catalog NGC 129

Physical size

9.8 light-years across — about 2.2× the Sun-to-Alpha-Centauri 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 59 of 363 members.

3Visibility

Set a location in User Settings to see visibility data.

Best season Aug – Oct (peak: Sep)

4 Eyepiece View

Telescope Eyepiece

125x TFOV: 0.4° Lim. mag: 13.6

NGC 129 · 5.4′ 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.