When is the best time to observe NGC 1817?

NGC 1817 is best observed from November through January, with peak visibility during December when it transits around midnight in the Northern Hemisphere.

Where is NGC 1817 located in the sky?

NGC 1817 lies in the constellation Taurus at right ascension 05h 12m and declination +16° 41′.

What telescope do I need to see NGC 1817?

At magnitude 7.7, NGC 1817 is easy in 7×50 or 10×50 binoculars.

NGC 1817 — Open Cluster in Taurus

Open Cluster Excellent (62/100)

Magnitude 7.7^m OpenCluster Taurus (Tau) Visible

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1Properties

Magnitude 7.7

Angular Size 9.3′

Description

Cl, L, Ri, lC, st 11...14

Position & Identifiers

RA 05h 12m 26.3s

Dec +16° 41' 02.8"

Constellation Taurus (Tau)

Catalog NGC 1817

Physical size

16 light-years across — about 1.8× 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 96 of 413 members.

3Visibility

Set a location in User Settings to see visibility data.

Best season Nov – Jan (peak: Dec)

4 Eyepiece View

Telescope Eyepiece

125x TFOV: 0.4° Lim. mag: 13.6

NGC 1817 · 9.3′ 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.