NGC 1647 — Open Cluster in Taurus
About NGC 1647
Description
NGC 1647 is a large, loose open cluster in Taurus, about 1,800 light-years away, sitting just over 3 degrees northeast of Aldebaran. It contains roughly 200 members spread across about 45 arcminutes — well over a full Moon's diameter — with the brightest stars at magnitude 8.5 to 9.5. The cluster is around 150 million years old, intermediate in age between the Pleiades and the Hyades, and is one of the more substantial open clusters in the constellation outside those two famous neighbours.
Observing Tips
A naked-eye-fringe target from dark skies, where it appears as a faint hazy patch east of Aldebaran. Binoculars and small telescopes give the most pleasing view — a 4-inch at low power frames the cluster comfortably, with several dozen stars resolved against the rich Taurus star field. Larger scopes oversample the loose distribution and tend to dissolve the cluster's coherence. Aim a half-degree-plus eyepiece field at the area between Aldebaran and Zeta Tauri to find it. Best observed November through March.
History
Discovered by William Herschel on 15 February 1784. NGC 1647 was a popular target in early systematic open-cluster studies because of its large size and easy location, and it featured in 20th-century photometric surveys aimed at calibrating the main-sequence ages of intermediate clusters.
Fun Facts
Despite being only about 4 degrees from Aldebaran in the sky, NGC 1647 is more than ten times farther away — the proximity is purely a line-of-sight coincidence. The cluster sits well beyond the Hyades, on the far side of the Local Bubble in the direction of the Galactic anticenter.
Observe
1Properties
Position & Identifiers
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 |
Bortle 3 = rural · 4 = outer suburbs · 5 = suburbs
3Visibility
Set a location in User Settings to see visibility data.
4
Eyepiece View
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.
Each point is a Gaia-DR3 member. Colour encodes spectral type; size reflects membership probability.
Explore
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.
Explore Nightbase
Related knowledge, tools, and stories — no observation planning required.
