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Cooling Tower Cluster (M29)

open cluster in Cygnus

M29, the Cooling Tower Cluster, is a small open cluster in Cygnus, a few degrees from Sadr (Gamma Cygni). It sits in a busy part of the Milky Way surrounded by glowing nebulosity, so it works best as a close-up inside a wider scene.

Save your telescope or lens on the planner to lay your camera frame over this diagram.

Approximate size and shape, drawn to scale. Not a photograph.

// Key facts

Catalog: M29
Type: open cluster
Constellation: Cygnus
Size: 7′ across
Brightness: Magnitude 7.1
Distance: about 4,000 light-years
Peak month (any location): Jul
Typical prime months: May to Oct
Difficulty: Intermediate
Filter: No filter (broadband)

// For your location

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How to image Cooling Tower Cluster

At 7 arcminutes it is small, so 1,000 mm or more for a close-up.
Alternatively include it in a wide frame with Sadr and the surrounding gamma Cygni nebulosity.
Cygnus is high in the northern summer sky.

Framing: what focal length?

M29 is small, so a "60% of the frame" focal length would be impractical. Here is how much of an APS-C frame it covers at common long focal lengths; expect to crop.

Focal length	Share of the frame width
1,000 mm	about 9%
2,000 mm	about 17%
3,000 mm	about 26%

How high does it climb from your latitude?

The highest point M29 reaches in the sky. Above about 60° is excellent, 30° to 60° is workable, and under 30° you are looking through a lot of air.

Latitude	Highest point	Rating
55°N (Scotland, Alaska)	74°	High in the sky
45°N (Minneapolis, Milan)	84°	High in the sky
35°N (Los Angeles, Tokyo)	86°	High in the sky
25°N (Miami, Cairo)	76°	High in the sky
35°S (Sydney, Santiago)	16°	Stays low

Also worth imaging

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