Since the early twentieth century when Edwin Hubble recognized that the Milky Way was not the only galaxy, it has been estimated that there are some two hundred billion galaxies in the observable Universe; the Milky Way is thought to contain about 250 billion stars +/- 150 billion.  Research in 2016 now suggests this might significantly underestimate the number of galaxies, which could exceed more than two trillion!

Perhaps the ultimate astrophotograph is the Hubble Ultra Deep field image.  At just one seventeenth a degree of the sky in size it shows objects up to some 13 billion light-years away, which is the furthest visible light image ever taken and contains some 10,000 galaxies.

Somewhat closer to home at a mere 2.5 million light-years, is our nearest neighbour M31, AKA the Andromeda galaxy.  Like the Milky Way, Andromeda is a spiral galaxy with a concentrated bulge of matter at the centre, surrounded by a disk of gas, dust and stars and an immense halo.  Andromeda and the Milky Way are moving inexorably together on a collision course at the rate of about 70 miles per second and are expeted to meet in about 4.5-billion years.  However, such is the space between the matter in each galaxy, the most likely outcome will not be a collision but the interaction of gravity between the opposing masses, leading to their eventual coalescence into a new giant galaxy.

Since starting astroimaging I’ve often returned to Andromeda at this time of the year ( 21/08/14 Meet the Neighbours, 09/10/15 Space Oddysey, 27/10/15 Overspill, 03/11/17 Galactic Neighbours), it is after all one of the magnificent features of the night sky.  At some 3^o x 1^o in size, with an apparent magnitude of +3.44 the galaxy completely fills the field-of-view of my equipment but I’ve always found imaging and particularly processing to be somewhat challenging.  As ever integration time is a major determinant of final image quality and this time I was able to obtain 7.5 hours over two nights, far greater than on previous occasions.   However, the overwhelming brightness of the galaxy’s core is always difficult to control during capture and processing and this was again to be the case.

Notwithstanding, I’m pleased to say that after four previous occasions imaging Andromeda, the combination of much greater integration time and better processing is this time evident in an improved image, which is overall more powerful.  Moreover, the galaxy’s internal structure has been enhanced with the addition of Ha-subs, which highlight large HII-areas of star formation that broadly follow the dust lanes.  However, you can never have too many subs and I’ll inevitably return again to this object in order to add to this year’s data and hopefully further improve processing so as to tame the subtleties that make Andromeda such a wonderful feature for astrophptography.