Given my dark mood early this morning I followed up NGC7635 with another visit to M42 for roughly two hours,  I called it a night by 02:00.   I used the Optolong L-Ultimate, but one of these nights I am going to try and not use an LP filter ( Bortle 7 Sky).   

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Messier 42 (M42), the famous Orion Nebula, is an emission-reflection nebula located in the constellation Orion, the Hunter. With an apparent magnitude of 4.0, the Orion Nebula is one of the brightest nebulae in the sky and is visible to the naked eye. It lies at a distance of 1,344 light years from Earth and is the nearest stellar nursery to Earth. The nebula has the designation NGC 1976 in the New General Catalogue.The Orion Nebula is very easy to find as it is located just below Orion’s Belt, a prominent asterism in the winter sky. The nebula appears as the fuzzy middle star in Orion’s Sword, which is formed by a vertical row of three stars (i.e. two stars and M42) south of Orion’s Belt. The nebula can easily be seen in binoculars and small telescopes. Covering more than a degree of apparent sky, the nebula appears over four times the size of the full Moon.Small telescopes at higher magnifications will reveal the four brightest stars in the Trapezium Cluster, an open cluster of young, hot, massive stars that were formed within the Orion Nebula. The four stars form a trapezoidal shape and energize the surrounding nebulosity.  The Orion constellation is easy to identify for its prominent hourglass shape, with the bright supergiants Betelgeuse and Rigel at the upper left shoulder and lower right foot of the celestial Hunter. Orion’s Belt, formed by the bright stars Alnitak, Alnilam and Mintaka, is in the centre of the hourglass figure. The best time of year to observe M42 is during the winter months, when Orion is high in the sky in the evening.Messier 42 occupies an area of 65 by 60 arc minutes of apparent sky and its spatial diameter measures 24 light years. The nebula has a mass 2,000 times that of the Sun and contains associations of stars, reflection nebulae, neutral clouds of dust and gas, and ionized gas. It is part of the Orion Molecular Cloud Complex, a larger region of nebulosity that also includes the famous Horsehead Nebula, the Flame Nebula, the emission nebula Barnard’s Loop, De Mairan’s Nebula (M43), and the reflection nebula Messier 78.The Orion Molecular Cloud Complex covers an area of more than 10 degrees, which is more than half of Orion constellation.The Orion Nebula is a place of massive star formation and one of the most studied deep sky objects in our vicinity as it allows astronomers to study the process of stars forming from clouds of dust and gas and the photo-ionizing effects of massive young stars that are responsible for the nebula’s glow. New stars are forming throughout the nebula. The temperature in the central region is up to 10,000 K and considerably lower around the edges.The stars in the Trapezium Cluster emit ultraviolet radiation, heating the surrounding gas and illuminating the nebula. Their stellar winds are also eroding and sculpting the nebula. Most of the ultraviolet ionizing radiation comes from Theta-1 Orionis C, the most massive of the four bright stars in the Trapezium Cluster and one of the most luminous stars known.Theta-1 Orionis C has the spectral classification O6pe V and the highest surface temperature (40,000 K) of any star visible to the naked eye. It emits 3 to 4 times more photoionizing light than the second brightest star in the cluster, Theta-1 Orionis A.Different parts of the Orion Nebula have been given different names. The bright regions to the sides of the nebula are known as the Wings and the dark lane stretching from the north toward the illuminated region is called the Fish’s Mouth. The wing extension to the south is known as the Sword, the fainter extension to the west is called the Sail, and the bright nebulous region under the Trapezium Cluster has been nicknamed the Thrust.Messier 42 contains hundreds of very young stars, less than a million years old, and also protostars still embedded in dense gas cocoons. The nebula is home to about 700 stars in different stages of formation. The youngest and brightest members are believed to be less than 300,000 years old, and the brightest of these may be as young as 10,000 years old.The Hubble Space Telescope has observed more than 150 protoplanetary disks, or proplyds, within M42. These are systems in the first stages of solar system formation.

@info from Messier-objects.com