M103-U-M M103 is a beautiful open cluster in Cassiopeia. This 16 million years/old cluster is one of the most distant open clusters from the Earth, lying in the Perseus' arm of the Milky Way at more than 9,000 Light Years from us.
Of the four brightest members of the cluster, the central red one is an M-type red giant, while the bluish one at the bottom left is a blue supergiant B5 and the smaller one just below the central red is a blue giant B2.
The brightest star on the top right is not belonging to the cluster but it is much closer to us and it is on the foreground just for prospective reasons. This star - Struve 131- is however a nice triple star system of which the brightest component is a blue giant.

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Telescope: Newton 10" F/4,8 + Coma Corrector
Camera: CMOS ASI 533 MC
Exp: 6x600"
Observatory: Home Observatory - Trivolzio (taly)