Two nights ago I pointed telescope one more time to M1 Crab nebula. Transparency was poor, but I was tempted with decent seeing. I was able to gather 150 minutes of light through hydrogen alpha filter. After some processing some detail was revealed.
M1 Crab nebula is supernova remnant. Corresponding supernova was recorded by Chinese astronomers in 1054, so the nebula itself is almost one thousands years old. Inside the nebula there is pulsar is neutron star or white dwarf that emits a beam of electromagnetic radiation. And it rotates. Each time the beam points towards Earth, a pulse can be observed. Pulsar in Crab nebula rotates over 30 times per second.
Image below was made with ACF 10″ telescope and QHY163M camera on EQ6 mount. It is 30 frames, 5 minutes exposure each, stacked and processed.
Large version here http://astrojolo.com/wp-content/uploads/2018/02/M1-raw.jpg