M 33 is the third largest galaxy in the Local Group, after the MilkyWay and M 31. The spiral structure is clearly visible in the images below. Initially discovered before 1654, the galaxy was rediscovered by Charles Messier in 1764. William Heschel also catalogued the galaxy in 1784, and it was among the first spiral nebulae identified by Lord Rosse. Edwin Hubble observed classical Cepheid stars in the galaxy, allowing him to demonstrate that M 33 was a galaxy in its own right.
For comparison, I've posted two images of M 33. The first consists of about 5 hours of data in 45 second segments, captured over two nights. The second is one night of data for comparison (2.5 hours in 45 second segments). Note the increase in the extent and detail of the galaxy in the longer exposure.
I have also included an astrometry annotated image, showing several of the galaxy's components visible in the pictures. Click and zoom for larger images. I have also added an image with clarity boosted to show details of the clouds of gas and dust near the core.
Tech card: RASA 8, DS10C, DMZ filter
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