М38 < М39 > М40 ...
Open star cluster M39
Open star cluster M39 is in the constellation Cygnus (Cyg).
Equatorial coordinates (epoch J2000):
Visual magnitude: 5,5m - this object can be seen with the naked eye on a black sky, in the absence of illumination from street lighting.
Optimum magnification for a telescope with observations of M39, depending on the aperture of the telescope (D), is about 10x-20x. Higher magnifications of course add details, but lead to a strong drop in the brightness of the image, making it difficult to observe.
Nikolay Kurdyapin, astro-map.com
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