M52 Star Hop: Finding the Open Cluster with a 114-150 mm Reflector

Before you start

The best months to observe M52 are October and November. In those months the cluster is well placed in the evening sky for observers in the Northern Hemisphere. At 35° N it climbs to about 63° above the horizon, and at 50° N it reaches about 78°, so it passes close to overhead from higher northern latitudes.

Plan the session around your sky conditions. A suburban sky has a naked-eye limit of about magnitude 5, and M52 is listed at magnitude 6.9. You will not see the cluster without a telescope, so the star hop is the main task. Use the finder scope and the lowest-power eyepiece you have for the search, then switch to a higher power to examine the group once you are on it.

Give your eyes at least 15 to 20 minutes to adjust to the dark before you begin. Bring a star atlas, either printed or as a planetarium app, and check the route against it at each step. A chart helps you confirm the star patterns and avoids confusing Cassiopeia with the nearby stars of Cepheus.

Star-hop route from Cassiopeia

The route runs in three stages: find a pattern you know, find the W of Cassiopeia, and then hop west to the target.

Step 1: Find the Big Dipper and Polaris

Locate the Big Dipper, the seven-star pattern in Ursa Major. Its two outer "pointer" stars, Dubhe and Merak, form the side of the bowl farthest from the handle. Draw an imaginary line through them, away from the bowl. Follow it for about five times the distance between the two pointers and you reach Polaris, the bright star that sits close to the north celestial pole.

Cassiopeia lies on the opposite side of Polaris from the Big Dipper, at a similar distance from the pole. If you can find the Dipper and Polaris, you can find Cassiopeia.

Step 2: Locate the W of Cassiopeia

Cassiopeia is a group of five moderately bright stars arranged in a W or M shape, depending on its orientation in the sky. From one end to the other, the five stars are Caph, Schedar, Navi, Ruchbah and Segin. Caph and Schedar form the first two points of the pattern, and Ruchbah and Segin form the last two.

Use the end of the W that lies closer to Cepheus, the faint constellation west of Cassiopeia. That end is Caph, and it is your starting point for the hop. Check that the five stars match your atlas before you move on, because a second pattern of similar brightness can be mistaken for the W.

Step 3: Hop west from Caph

From Caph, M52 lies about 5 to 6 degrees to the west, with a slight northward offset. To judge that distance without a setting circle, hold your fist at arm's length. Its width is roughly 10 degrees, so the target lies about half a fist west of Caph.

Scan that area with the finder scope and look for a small, dense group of stars. Stars of similar brightness clustered together in a patch that stands out from the background are your signal to move to the eyepiece.

Another useful reference is the Bubble Nebula, which lies well under a degree from M52, to the west and slightly south. It is faint, and in a suburban sky it may be hard to see, but its location helps confirm that you are in the right field. You will return to it in the next section.

Confirming you have arrived

Once the cluster is in the field of your telescope, check it against your chart and the following features.

First, look at the group itself. M52 should appear as a clump of stars that are noticeably brighter than the surrounding field. At low power, the stars are distinct points, not a haze, and the group covers only a small part of the view. Its apparent width is about 10 arcminutes, roughly a third of the width of the full Moon.

Second, compare the pattern with your atlas. The arrangement of the brighter members should match the chart when you adjust your orientation. If the pattern does not match, move the telescope gently to examine nearby fields before you conclude that you are on target.

Third, check the Milky Way background. M52 is set in a rich band of stars, so the surrounding field should look denser than a random patch of sky. If the field around the group is almost empty, you may be too far from the Milky Way, or you may be looking at a different area of Cassiopeia.

If you are confident of the cluster, try to find the Bubble Nebula. Use low power and a dark-adapted eye, and move the telescope slowly across the area to the west and slightly south of the cluster. In a suburban sky the nebula is faint and may only show as a subtle, rounded brightening. An oxygen-III filter can increase its contrast, but the nebula may still remain difficult to see.

What you will see with a 114-150 mm reflector

At low power, roughly 30x to 50x, M52 resolves into a group of individual stars. This is the view described as the expected result for this class of telescope: a clear group of separate points, with some stars brighter than others. The cluster is compact, so its stars appear crowded together at the center of the field.

At higher power, around 60x and above, the stars spread out and the view becomes dimmer. Higher power can help you separate close pairs of stars within the group, but it can also make the cluster harder to find. Start at low power, confirm the cluster, and then test higher magnifications if the view is steady.

In a suburban sky, the background brightness reduces contrast. Faint members of the cluster may not show, and the group may look smaller than the chart suggests. This is normal. Judge the view by the bright members you can count, not by the faintest stars you hope to see.

Keep your expectations realistic. M52 is a pleasant, easy target for a telescope of this size, but it does not reveal dramatic detail. Its appeal lies in the way the stars separate and sit against the Milky Way.

Visibility by latitude

Visibility depends on where you observe from.

At 35° N, M52 reaches about 63° above the horizon. It is high in the sky during the evening in October and November, which makes the hop straightforward and gives a steady view.

At 50° N, the cluster climbs to about 78° and sits close to overhead. The route from Cassiopeia is the same, but the cluster is near the zenith, so the telescope's position is more awkward. A comfortable eyepiece angle and a stable mount help in that case.

At 35° S, M52 never rises above the horizon. Observers in the Southern Hemisphere at that latitude cannot see the cluster, so they should choose targets that rise at their location.