When is the best time to observe NGC 7128?

NGC 7128 is best observed from July through September, with peak visibility during August when it transits around midnight in the Northern Hemisphere.

Where is NGC 7128 located in the sky?

NGC 7128 lies in the constellation Cygnus at right ascension 21h 44m and declination +53° 43′.

What telescope do I need to see NGC 7128?

At magnitude 9.7, NGC 7128 is within reach of a 3-inch (80 mm) telescope from a moderate-Bortle site.

NGC 7128 — Open Cluster in Cygnus

Open Cluster Fair (39/100)

Magnitude 9.7^m OpenCluster Cygnus (Cyg) Visible

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1Properties

Magnitude 9.7

Angular Size 3.0′

Description

Cl, S, pRi, has a ruby *9.5

Position & Identifiers

RA 21h 44m 00.0s

Dec +53° 43' 00.0"

Constellation Cygnus (Cyg)

Catalog NGC 7128

Physical size

12 light-years across — about 1.4× the Sun-to-Sirius distance

2How easy to spot?

Telescope	Bortle 3	Bortle 4	Bortle 5
80 mm refractor 80mm refr.	Easy	Medium+	Medium
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

Medium on Seestar S50

At 150mm under B5 skies you should resolve about 13 of 168 members.

3Visibility

Set a location in User Settings to see visibility data.

Best season Jul – Sep (peak: Aug)

4 Eyepiece View

Telescope Eyepiece

125x TFOV: 0.4° Lim. mag: 13.6

NGC 7128 · 3.0′ 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.