The Andromeda Galaxy

I wasn't sure whether to post this or not as it is not strictly a photograph taken today. It includes some photographs taken today, or at least just after midnight, but actually consists of a stack of 483 thirty seconds exposures acquired over nearly two weeks.
By stacking many images more detail can be prised out with less noise. This image still needs a lot of processing work but as space is so awesome I wanted to share it. I will be building up more exposure time on M31 as the year goes on.
As we look at the night sky we look back in time because distances are so vast. M31, the Andromeda Galaxy, is 2.537 million light years away so we are seeing it as it was that many years ago. It is like our own Milky Way galaxy but bigger, about 200,000 light years in diameter. This means that although we look at the whole galaxy the light from the part nearer to us is 200,000 years ahead of the far side! I know, it's mind-blowing stuff!
As to how we know the distance to M31 with such apparent precision; that's for another day.
To get the image I attached my Pentax K5 to a 72mm diameter telescope and set it on a portable tracking mount to follow the motion of the sky.