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NGC 752
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NGC 752 (also Melotte 12, Caldwell 28, Collinder 23 and OCL 363) is a magnitude +5.7 open star cluster located 1,300 light-years away in the constellation Andromeda.

The galaxy was discovered by Italian astronomer Giovanni Battista Hodierna with probably a 1-inch 20x Galilean telescope in the castle of his patron Carlo Tomasi et Caro, in Palma di Montechiaro sometime before 1654.
The cluster was rediscovered by William Herschel on the 24th August 1783.
The cluster was rediscovered by Caroline Herschel on the 29th September 1783.

Right Ascension 01h 57m 55.0s, Declination +37 51' 57"

A telescope reveals about 60 stars no brighter than 9th magnitude within NGC 752
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NGC 752



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Caldwell 28
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NGC 752 (also known as Caldwell 28) is an open cluster in the constellation Andromeda. The cluster was discovered by Caroline Herschel on September 29, 1783 and catalogued by her brother William Herschel in 1786, although an object that may have been NGC 752 was described by Giovanni Batista Hodierna before 1654.
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Title: Seven-color Vilnius photometry of the open cluster NGC 752
Authors: S. Bartasiute, V. Deveikis, V. Straizys, A. Bogdanovicius
(Version v2)

New photoelectric seven-colour observations in the Vilnius system are presented for 65 stars in the region of the open cluster NGC 752. Based on individual stars with accurate photometric classifications, we determine the apparent distance modulus (m-M)=8.38 and the mean reddening to the cluster E(Y-V)=0.027, or E(B-V)=0.034. The mean photometric metallicity for the main-sequence stars, [Fe/H]=-0.14, is found to be slightly lower than that derived for the red clump giants, [Fe/H]=-0.08. This difference suggests that red giants in later evolutionary phases may not have zero-age surface values of [Fe/H]. We made use of the least-squares minimization techniques to fit the Padova theoretical isochrones to the CMD, when the binary star population is taken into account. By varying the distance modulus, metallicity and age, the best match has been found between the seven magnitudes and colours of the observed stars and those of model binaries, which gives the distance modulus by 0.2 mag smaller than that derived from individual stars, i.e., (m-M)=8.18, a closely similar metallicity ([Fe/H]=-0.12), and age of 1.6 Gyr. With these results, the fraction of photometric binaries among the main-sequence stars is ~40%.

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