NGC 752 is a large sprawling open cluster in the constellation of Andromeda. With an apparent magnitude of +5.7 it's visible to the naked eye from a dark site, appearing as a large unresolved fuzzy patch of light. The cluster is one of the finest large open clusters in the sky and contains over 70 stars spread across a huge 1.25 degrees of apparent sky. Due to its size, NGC 752 is best observed with binoculars or wide field telescopes at low powers.
NGC 752 is located 5 degrees south and slightly west of outstanding double star Almach (γ And - mag. +2.1), the third brightest star in Andromeda. This cluster was discovered by Caroline Herschel on September 29, 1783 although it was probably observed sometime before 1654 by Italian astronomer Giovanni Battista Hodierna. Caroline's brother, William Herschel, subsequently added it to his catalogue a couple of years later.
NGC 752 is best seen from northern latitudes during the months of October, November and December. It's number 28 in the Caldwell catalogue.
NGC 752 is a delightful open cluster when seen through binoculars, small or wide field telescopes. Through popular 7x50 or 10x50 models, it appears large and hazy with the brightest dozen stars resolvable. An 80mm (3.1-inch) scope at low powers reveals approximately 60 mainly white stars. However even with a wide field eyepiece, it doesn't take much magnification before it overfills the field of view. When seen through medium size scopes, such as 150mm (6-inch) instruments, NGC 752 is a wonderful site with a myriad of stars visible including some colourful members.
In total, NGC 752 contains about 60 stars brighter than 9th magnitude. It's located 1,300 light-years distant and has an age of about 2 billion years.
NGC 752 Data Table
|Object Type||Open Cluster|
|RA (J2000)||01h 57m 48s|
|DEC (J2000)||+37h 51m 00s|
|Apparent Size (arc mins)||75 x 75|
|Age (years)||2 Billion|
|Number of Stars||>70|
|Other Name||Collinder 23|