Colorful nebulae in Orion you can see in winter
Now is the best time to get out your telescope and eyepieces or camera to observe the amazing deep sky around the constellation Orion. Probably the best known object is Messier 42, the Great Nebula in Orion, in the sword a bit below the belt stars. There are other less frequently seen nebulae in Orion, such as the Horsehead Nebula (IC434) in Orion’s belt, a dark nebula next to an H-II star-forming molecular cloud region about 1400 light years away from us. Another interesting Orion object is the lesser known Monkey Head Nebula (NGC 2174), an emission nebula in Orion’s upper arm above the bright star Betelgeuse. These were my targets during a couple of clear nights around Christmas (see the images in the Nebulae Gallery).
For each of these two Orion nebulae, data were collected for ~5 hours with 15 min subexposures using a color sensor CMOS camera and 12.5” reflector telescope, along with a guidescope equipped with CCD guide camera. In the resulting images I was surprised by the appearance of what seems like beams of blue rays shining down onto the Horse’s Head, like rays of hope and inspiration in the heavens! Actually the blue beam in the image is a diffraction effect due to the bright star Alnitak (mag 1.8) just above the field of view. The Monkey Head Nebula (Figure below) emits mainly red light of ionized hydrogen from a gigantic H-II region of condensing interstellar gases where new stars are continually being born, about 6500 light years away. The surrounding star field is catalogued as the open cluster NGC 2175.