М39 < М40 > М41 ...
Optical pair of stars M40
Optical pair of stars M40 or Winnecke 4 gromada is in the constellation Ursa Major (UMa).
Equatorial coordinates (epoch J2000):
Visual magnitude: 9m
Optimum magnification for a telescope with observations of M40, depending on the aperture of the telescope (D), is about >10x. 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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