Messier 39

Messier 39 (M39), also cataloged as NGC 7092, is a large, loosely bound open star cluster located in the northern constellation of Cygnus, the Swan. It is sometimes nicknamed the Pyramid Cluster because its brightest stars align to form a distinctive triangular shape against the sky.

Key Characteristics

> Distance and Location: It is located roughly 800 to 1,050 light-years from Earth, making it one of the closest Messier objects to our solar system. It can be found roughly 9° east-northeast of the bright star Deneb.

> Size: The core cluster spans about 7 to 37 light-years in true physical diameter. In the night sky, it has an angular size comparable to or larger than the full Moon. Recent data from the Gaia satellite has revealed a massive, hidden surrounding "corona" of stars spanning 20 degrees across the sky, composed of stars that are slowly escaping the cluster's gravity. 

> Composition and Stellar Content: It is a relatively sparse, young cluster containing roughly 30 to 50 confirmed stars. Its stars are estimated to be between 200 and 300 million years old—far younger than our Sun. Its brightest members are hot, blue main-sequence stars, though some are beginning to transition toward their red giant phase.

> Discovery: The cluster was first discovered by French astronomer Guillaume Le Gentil in 1749 and was later cataloged by Charles Messier in 1764.

Imaging Telescope: Vixen ED81s f/5.2

Mount: Skywatcher HEQ5 Synscan Pro (belt mod) 

Camera: QHY 533M 

Filter Wheel: QHY CFW3S-SR 

Guiding camera: ZWO ASI120MM Mini (mono)

Guidescope: SkyWatcher EvoGuide 50ED

Constellation: Cygnus

Date: 5 Aug 2026 

Location: Albireo Observatory 2, Ileia, Greece

Sky brightness: B2

Exposure Time: 

L: 80x120 sec (gain: 56.00, offset: 12.00) 0°C bin 1×1 

R: 40x120 sec (gain: 56.00, offset: 12.00) 0°C bin 1×1 

G: 40x120 sec (gain: 56.00, offset: 12.00) 0°C bin 1×1 

B: 40x120 sec (gain: 56.00, offset: 12.00) 0°C bin 1×1 

Acquisition: N.I.N.A 

Processing: Siril, Pixinsight, Photoshop