Historical notes. - According to this author, NGC752 was discovered by Giovan Battista Hodierna before 1654. The Sicilian astronomer described it, together with M33, in his "De Admirandis Coeli Characteribus" (printed in 1654 in Palermo) as "quae iuxta Triangulum, hinc inde duplex", i. e. "that [nebula] close to Triangle, double or going from one side to the other" (see "De Admirandis...", pp. 7, 11, 48).

Dreyer speaks of it having both "large" and "small" stars.

To observe NGC752. - NGC752 is a large and scattered cluster of fairly bright stars. It lies about 4.8° SSW of g Andromedae and just W. Its large size (about 50' in diameter) and its total magnitude of 5.7makes its best impression in good binoculars or in small rich-field telescopes, with low-power eyepieces.

Its brightest stars (about fifteen out of some sixty likely members) range from 9th to 10th magnitude; the faintest reach the 12th magnitude. Large Dobsonians may notice many faint mag. 15+ galaxies throughout the area. One "bright" (at mag. 13.1) exception is IC179

The stars of NGC752 and its H-R diagram. - Although not spectacular to visual observations, this cluster is very interesting for other ways. Its H-R diagram, instead, shows a somewhat intermediate trend between the normal galactic clusters and the globulars in the matter of age and evolutionary development. Its structure and motion class it as a galactic cluster, but the stellar population is evolving toward the typical pattern of a globular's H-R diagram.

Dana I. Dinescu, Pierre Demarque (Yale University), D. B. Guenther (Saint Mary's University Halifax) and M. H. Pinsonneault (Ohio State University), using Improved Opacities and Cluster Membership Data, derived the ages of M67, NGC188 and NGC752. For NGC 188 and M67 they derive the ages, respectively. 6.0±0.5 billion years and 4.0 ±0.5 billion years (the main uncertainty is due to the estimate of the interstellar reddening). The age of NGC 752 is 2.0±0.5 billion years.

Per chiarimenti, osservazioni o suggerimenti prego contattare demaria@telegest.it