Pleiades (M45) with the Naked Eye: What the Cluster Looks Like

What you see with your eyes

Start with the group itself. Under a suburban sky you will usually count six or seven stars in a compact cluster. The bright core spans roughly a degree of sky, about two Moon widths, so it fits comfortably in the space between your thumb and little finger held at arm's length.

The shape of the group

The stars form a small, loose dipper, a pattern often compared to a miniature Big Dipper. Use the brightest member, Alcyone, as your anchor. Alcyone lies near the middle of the group, and the other bright stars spread around it. Atlas and Pleione sit close together and are easy to pick out as a near pair. Maia, Merope, Electra, Taygeta and Celaeno fill in the rest, and the fainter ones are the first to disappear when conditions worsen.

Do not expect the separation between stars to look wide. The whole group is compact, and the stars appear more crowded than most people expect the first time they look.

Brightness and color

The cluster has a combined brightness of magnitude 1.2 (V), so it stands out even from a town. You do not need a dark site to notice it. The individual stars are fainter than the group as a whole, and under suburban skies only the brighter members are reliably visible. Whether you can see the fainter stars depends on your eyesight and how dark your adapted eyes become.

The stars are blue-white. Look at Alcyone and its nearest neighbors on a clear night and you should see a cool, bluish tint, which is most noticeable when the stars are high above the horizon and the air is steady. The color is subtle, so compare the cluster with a clearly orange star such as Aldebaran to see the contrast.

The haze

Under a suburban sky the cluster reads as a hazy patch around the brighter stars. The haze is faint bluish nebulosity that surrounds the group and is caused by dust reflecting the cluster's light. It has no sharp edge, and its outer parts blend into the background sky. The overall patch spans about 2.5 degrees, roughly five Moon widths, so it is larger than the group of bright stars at its center.

Do not expect structure in the haze. Under a suburban sky you will see a soft glow, not individual wisps or lanes. Dark skies and a steady, transparent atmosphere are needed before the haze shows more detail to the naked eye.

Finding it in the sky

Pleiades is easy to locate because it sits in a region of sky with several bright stars. Use a planetarium app or star chart to confirm its position against the coordinates in the facts table, then match what you see to the directions below.

From 50° N

At 50° N the cluster culminates at an altitude of 64°. In December and January evenings it is high in the sky, well placed for observation after dusk. Start with Orion, then look for Aldebaran, the orange star of Taurus. The Pleiades lies a few degrees from Aldebaran, in the same part of the sky. Once you have Orion and Aldebaran, the cluster is hard to miss.

From 35° N

At 35° N the cluster reaches 79° at culmination, almost overhead. This is very high and can cause neck strain. Use a reclining chair or lie on a blanket so that you can view it without tilting your head for long periods. The cluster is easy to find at this latitude, but you may need to check your star chart to confirm which bright stars are members and which are background stars nearby.

From 35° S

From 35° S the cluster reaches only 31° at culmination, and it stays low in the northern sky. You need an open view to the north, free of buildings, trees and street lights close to the horizon. Look soon after dark in December and January, before the cluster sinks further toward the horizon. Because the cluster is low, the air between you and the stars is thicker, so the haze and fainter members will appear dimmer than they do from northern latitudes.

How conditions change the view

Conditions affect the haze more than the bright stars. The bright members remain visible under most conditions, but the haze can be lost entirely if the sky is unfavorable.

Moon phase

A bright Moon washes out the haze and can hide the fainter stars. A full Moon nearly eliminates the nebulosity from view. A thin crescent or a Moon below the horizon gives the best chance of seeing the haze. Check the Moon's phase and position before planning a session.

Light pollution

Street lighting and nearby buildings raise the background brightness of the sky. Under a suburban sky the bright stars still appear clearly, but the haze fades quickly. Shield your eyes from nearby lights, step into the shadow of a building or wall, and allow your eyes time to adjust after you leave a lit area.

Transparency and humidity

Clear, dry, cold nights give sharper stars and a more defined haze. Humid nights and thin cloud or haze near the horizon scatter light and reduce contrast. Dew can form on your eyeglasses or on a viewing window, so carry a cloth and check the lenses often.

Altitude in the sky

The cluster appears brighter and clearer when it is high in the sky, because its light passes through less of the atmosphere. Observe it when it is well above the horizon whenever you can, especially at 35° S, where it never climbs far.

Techniques that help

Dark adaptation

Allow your eyes 15 to 20 minutes in the dark before you start looking for faint members. Avoid white light during this time. A red torch preserves your night vision, and you can use it to read a star chart without losing the sensitivity you have built up.

Averted vision

Look slightly to the side of the cluster rather than straight at it. The edges of your retina are more sensitive to faint light, so fainter stars and the haze can become easier to see. Move your gaze in small steps and watch the patch as you do.

Comparing with binoculars

Binoculars are useful for comparison, not as a replacement for the naked-eye view. A 10x50 binocular shows several dozen stars in the group, and the haze appears more extended across the field. The naked-eye view shows only the brighter members, but it gives you the overall shape and color that binoculars can make harder to judge. Use the naked-eye view first, then compare it with binoculars to see how many fainter stars were hidden.