Messier 35 (M35) is a large open star cluster located in the northern constellation Gemini. The cluster consists of several hundred stars, of which 120 are brighter than magnitude 13. The cluster has an apparent magnitude of 5.3 and lies at an approximate distance of 2,800 light years from Earth. The estimated age of M35 is about 110 million years. The hottest blue/white main sequence stars in the cluster have the spectral classification B3. M35 also contains more evolved stars, including several orange and yellow giants. The cluster is approaching us at 5 km/s. Another open cluster, NGC2158, lies about 15 arc minutes to the southeast of M35. NGC2158 has a visual magnitude of 8.6 and occupies an area of 5 arc minutes. It is considerably older, more compact and contains more stars. It is also more than five times more distant than M35 and the two clusters are not physically related.
Messier 35 (L) and NGC2158 (R)
Telescope: 16″ f3.75 Dream Scope
Camera: FLI ML16803
Mount: ASA DDM85
Exposure: 5 hours (36x300s L + 3x8x300s RGB)
Date: December 2019 – January 2020
Location: Southern Alps, France