About image M 35 (near the center of the image) and NGC 2158 (on the right) make up a nice pair of open clusters in the constellation Gemini. M35 apparently measures about 30' and contains about 200 components included between magnitudes 8.3 and 13. The distance has been estimated in about 2800 light years, which is equivalent to a real size of about 24 light-years in diameter; the age was instead indicated for 110 million years. NGC 2158, on the other hand, is a much weaker cluster due to the greater distance at which it is located, more than 16,000 light years: therefore it also appears strongly obscured by interstellar dust that is interposed along the line of sight.
Technical data Optic Tecnosky Apo Refractor 115 - 800mm f/6.9 Mount 10Micron GM1000 HPS Camera Atik 4000 with Starlight external filter wheel 5 positions Filters Baader RGB 50.8 unmounted Guiding system 10Micron GM1000 HPS Exposure details R 8x300" bin1 -20C G 8x300" bin1 -20C B 8x300" bin1 -20C Total integration 2h Acquisition Maxim, PHD2 Processing Pixinsight 1.8, Photoshop CS5 SQM-L 21.0 Location Pian dell'Armà (Pavia, Italy) Date 29 October 2016