In a summer season sky showcasing quite a few sensible examples of youthful and energetic open star clusters lies NGC 6791 in Lyra, a seemingly nondescript open cluster. Nonetheless, look extra intently at photographs of it and it is best to comment upon the bizarre yellowish tint of its teeming stars, giving it the looks not of a well-recognized open cluster however quite of a free globular cluster, a type of historical balls of star which were round virtually so long as the Universe itself. Therein lies the clue to its uniqueness; NGC 6791 is an amazingly historical open cluster, an anomaly that’s held itself collectively for round an unbelievable 10 billion years, making it maybe the second-oldest open cluster after Berkeley 17 in Auriga!
Find out how to observe
NGC 6791 is properly positioned on August nights; positioned below 10 levels east of sensible Vega (alpha [α] Lyrae), it rides excessive and could be noticed all through the darkening nights. Theta (θ) lyrae (magnitude +4.3) is a really helpful marker, positioned as it’s only a diploma east-north-east of NGC 6791.
NGC 6791 shines with an built-in magnitude of +8.2 and spans a considerable 16 arcminutes in obvious diameter. An 80mm (~three-inch) telescope will choose up it up with little issue on a clear and moonless night time; The Moon’s part is beneficial till that final week or so of August.
When you’ve tracked it down, don’t count on to see something apart from an eighth-magnitude fuzz ball, even in the event you ramp up the magnification. The cluster’s brightest particular person member stars, of which there are regarded as near 400, shine as faint as eleventh-magnitude and are past the decision of a telescope below 250mm (10-inches) in aperture. A ’scope of this measurement will partially resolve NGC 6791 and enhance the cluster to round 10’ in obvious diameter.
Pictures taken by medium- to large-aperture telescopes can actually carry out the traditional nature and unsung great thing about this wonderful cluster.
