NGC 663 is a bright, richly populated open star cluster tucked into the heart of the Milky Way’s flow through Cassiopeia, offering a rewarding view for stargazers of all experience levels. Composed of dozens of stars concentrated in a tight, slightly irregular shape, it resembles a patch of frost in the sky. The cluster shines with youthful energy—containing hot blue stars and a few evolved red giants—and spans about 15 arcminutes, making it an ideal target for both wide-field and mid-power observations.
What makes NGC 663 especially enticing is its placement in a trio of open clusters, nestled alongside NGC 654 and NGC 659. This creates a compact, deep-sky tour where observers can hop from one stellar gathering to the next.
NGC 663 is by far the brightest and easiest of the three. It is rich, compact, and densely populated, easily visible even in small scopes or binoculars as a concentrated glow with several bright stars resolved. NGC 654, appearing somewhat fainter and more condensed, is best enjoyed in medium to large telescopes. NGC 659, the faintest of the three, requires darker skies and higher magnification to resolve clearly. It is the challenge cluster of the three.
Finding NGC 663 is simple: locate Cassiopeia’s “W” asterism, and focus on the two eastern stars—Segin (Epsilon Cassiopeiae) and Ruchbah (Delta Cassiopeiae). The cluster lies about halfway between them, but just 1° south of the line connecting the two, making it a quick and satisfying hop with binoculars or a finder scope. The others are just a half degree away.
Whether you’re scanning with a small telescope or diving deeper with a larger one, NGC 663 offers a rich visual experience—and a gateway to one of the most cluster-rich regions of the northern sky.
C10 (NGC 663)
Rating: 🟢 Solid Catch
Level: 🔵 Easy
How:
When: Sep to Feb
🌟 A Bright, Eye-Catching Cluster NGC 663 stands out for its brightness and density, even in modest apertures or under suburban skies. It offers a concentrated gathering of stars, with a bright central region and fainter members that radiate outward. Its sparkle contrasts beautifully against the surrounding Milky Way, making it visually rewarding whether you’re using binoculars or a telescope.
🌟 Part of a Beautiful Cluster Trio NGC 663 is the brightest member of a compact group of three open clusters that includes NGC 654 and NGC 659. All three lie within a small region of Cassiopeia, making it easy to hop from one to the next in a single observing session. This trio adds depth and variety to your night, offering different star patterns and brightness levels to compare and enjoy.
🌟 Easy to Locate in Cassiopeia Finding NGC 663 is refreshingly simple, even for beginners. Just identify Segin and Ruchbah, the two eastern stars of the familiar W-shaped Cassiopeia. The cluster lies about halfway between them, but slightly below—around 1° south of the imaginary line connecting the two. A finder scope or binocular sweep is often enough to spot it as a hazy patch of starlight, and a telescope will quickly bring it to life.
🌟 Ideal for a Range of Equipment Whether you’re using binoculars, a small refractor, or a larger telescope, NGC 663 delivers. Binoculars reveal a soft glow or star-knot, small scopes resolve its brighter stars, and larger scopes bring out finer detail and texture. It scales beautifully with magnification, making it a satisfying return target as your gear or skill grows.
🌟 Rich Structure and Color Variety NGC 663 has more to offer than just brightness. Its slightly irregular shape gives it character, and in larger apertures, you may detect subtle color variations—bluish-white young stars mixed with a few warmer, redder giants. The layered appearance and diversity of brightness levels provide depth, making it a more interesting and engaging object to study than many looser open clusters.
🌟 A Stellar Highlight of Cassiopeia’s Star Fields Cassiopeia is one of the most cluster-rich regions in the northern sky, and NGC 663 is a standout among them. Observing it not only gives you a rewarding individual target but helps you appreciate the stellar density and variety that defines this part of the Milky Way. It’s a perfect entry point for deeper cluster exploration and one of the constellation’s brightest non-Messier treasures.
Open cluster: a loose group of a few dozen to a few thousand young stars that formed together and are loosely bound by gravity.
C10 (NGC 663)
The best way to star hop to NGC 663 is by using the distinctive “W” shape of the constellation Cassiopeia as your starting point.
Begin by identifying the constellation’s distinctive “W” shape, which is made up of five bright stars. Find Segin (Epsilon Cassiopeiae)(+3.34), the easternmost star in the W, and brighter Ruchbah (Delta Cassiopeiae)(+2.68) which lies 10° to the west of it, forming the eastern “arm” of the W.
Now, draw an imaginary line from Ruchbah to Segin and find its midpoint, 5° from either star. Using binoculars or finder, point to that location. Then pan about 1° south (downward) from the midpoint of that line. That spot marks the location of NGC 663. In a finder scope or binoculars, NGC 663 will appear as a faint, fuzzy patch—distinct from the surrounding star field. A low-power telescope view will start to resolve the cluster into a glittering group of stars, and switching to medium power will bring out its full richness.
To find NGC 654, gently pan your telescope north 0.5° of NGC 663. It appears tighter and more compact, and may look like a small knot of stars. To find NGC 659, slowly pan south 0.5° of NGC 663. Use averted vision—looking slightly to the side to make the fainter stars stand out better.
C10 (NGC 663)
✅ Observe on a Moonless, Clear Night Though NGC 663 is bright enough for moderate skies, NGC 654 and especially NGC 659 benefit greatly from dark, transparent conditions. Plan your observation on a moonless night to bring out the full richness of the region’s star fields.
✅ Start with NGC 663 Begin with NGC 663, the brightest and easiest of the trio to spot. Center it in your finder scope or low-power eyepiece—it appears as a compact cluster of stars midway between Segin and Ruchbah in Cassiopeia, just 1° below their connecting line.
✅ Use Low to Medium Magnification Low power will help you frame all three clusters in the same general region. NGC 654 and 659 are just over 0.5° away from NGC 663 but in opposite directions. Use medium magnification to pull out fainter stars and the structure of each cluster.
✅ Scan Slowly North to Find NGC 654 After observing NGC 663, gently pan your telescope northward 0.5° to reach NGC 654. It appears tighter and more compact, and may look like a small knot of stars.
✅ Use Averted Vision to view NGC 659 From NGC 663, slowly pan south 0.5° to reach NGC 659. It is the most subtle of the three, especially under light-polluted skies. Use averted vision—looking slightly to the side of the cluster—to make the fainter stars stand out better. Allow your eyes a moment to adapt to the contrast in the field.
✅ Compare Cluster Structures Take a moment to study the different shapes and densities of each cluster. NGC 663 has a wide, wing-like shape; NGC 654 is rounder and more concentrated; NGC 659 is looser and more dispersed. Observing how each cluster appears is a great way to sharpen your skills.
C10 (NGC 663)
❌ Naked Eye
With the naked eye, NGC 663 is not visible under most conditions. Even from very dark skies, its light is too faint and spread out to be detected without optical aid. However, its location in the dense star fields of Cassiopeia may give the impression of an extra richness in that region, hinting that something more lies within.
✅ Binoculars
Through binoculars, NGC 663 appears as a small, faint fuzzy patch—just slightly condensed compared to the surrounding star field. You won’t resolve individual stars, but it stands out as a soft glow, hinting at its clustered nature. It’s enough to confirm its location and frame it nicely within the Milky Way background.
✅ Small Telescope
A small telescope reveals the brighter members of the cluster, often in a loose grouping with a somewhat irregular outline. Dozens of stars begin to resolve, with a noticeable concentration toward the center and some brighter stars outlining a rough V-shape or wedge. The surrounding field sparkles with background stars, enhancing the contrast.
✅ Medium Telescope
With a medium telescope, NGC 663 becomes rich and textured. Many more stars are resolved, including fainter ones that form branching arms and subtle internal groupings. The brighter stars stand out with crisp clarity, and the cluster begins to show its full complexity and uneven structure.
✅ Large Telescope
In a large telescope, NGC 663 turns into a true stellar jewel. The field becomes densely populated, with fine resolution across the entire cluster. Faint stars fill in the gaps between brighter members, and color differences—particularly hints of warm tones in some evolved stars—may begin to emerge. The overall impression is that of a vibrant, populous gathering of stars suspended in the rich star fields of Cassiopeia.
C10 (NGC 663)
NGC 663 is visible under a range of conditions, but it thrives in dark skies. From Bortle 1–4, it displays its full richness and structure; from Bortle 5 onward, its beauty gradually fades, with much of its fine detail lost in brighter skies.
🟣 In Bortle 1–2 skies, NGC 663 appears as a richly textured, sparkling cluster set against a dense background of Milky Way stars. Its full extent and shape are easily appreciated, and even its fainter members stand out cleanly with good contrast and definition.
🔵 Under Bortle 3–4 skies, the cluster still offers an impressive view. The brighter stars remain crisp and plentiful, but the background star field loses some density, and the dimmest members may start to fade slightly. The overall shape remains distinct and engaging.
🟢 In Bortle 5–6 skies, NGC 663 begins to lose some of its richness. The brightest stars are still visible and form a recognizable core, but the finer texture and more subtle structure start to wash out. Light pollution reduces the surrounding star field, making the cluster appear more isolated.
🟠 Under Bortle 7+ skies, NGC 663 becomes a much less rewarding target. Only its brightest members may be visible, and the surrounding Milky Way is heavily diminished. The cluster looks sparse, and much of its visual appeal is lost in the skyglow.
C10 (NGC 663)
DSOs within 48° or 2 outstretched hands at arm's length
C10 (NGC 663) - the Heart of a Trio of Clusters
Begin by identifying the constellation’s distinctive “W” shape, which is made up of five bright stars. Find Segin (Epsilon Cassiopeiae)(+3.34), the easternmost star in the W, and brighter Ruchbah (Delta Cassiopeiae)(+2.68) which lies 10° to the west of it, forming the eastern “arm” of the W.
Now, draw an imaginary line from Ruchbah to Segin and find its midpoint, 5° from either star. Using binoculars or finder, point to that location. Then pan about 1° south (downward) from the midpoint of that line. That spot marks the location of NGC 663. In a finder scope or binoculars, NGC 663 will appear as a faint, fuzzy patch—distinct from the surrounding star field. A low-power telescope view will start to resolve the cluster into a glittering group of stars, and switching to medium power will bring out its full richness.
