M31 – Andromeda Galaxy

The following evening after I shot Messier 51, was again clear. The seeing wasn’t as good as the night before as it was ever so slightly warmer, but was still clear enough all night.

After my failed attempt at M33, I decided to go for something a little easier. Andromeda is our closest galactic neighbour, a larger version of our own galaxy, that’s 2.5 million light years away.

It’s been known for some years that eventually the Milky Way and Andromeda will collide; nearest guess is in about 3.7 billion years. So there’s nothing to worry about just yet! However, recently released data from the European Space Agency’s Gaia Satellite, reveals that there’s a third contender in the battle. Ironically it’s the galaxy I failed to capture the previous night – M33 – Triangulum Galaxy. This galaxy won’t collide with the Milky Way and Andromeda, but it’s gravitation pull will still affect the galaxy-pair. More about this can be read here.

As it’s still the height of summer, Andromeda is still pretty low on the horizon at 11PM, and slowly gains height during the night. To get imaging earlier, I decided to move slightly on my patio to allow me to get over the garage roof. I set up as per usual, using the spirit bubble level to make sure the tripod was level before aligning the head to Polaris.

Polar alignment seemed to go perfectly in the polar scope, but when it came to star alignment, my polar error was all over the place. It was giving me errors in the region of 00º30′30″ for both the right ascension and declination axis’s. I decided to use the polar alignment error correction using Arcturus as my reference star. It slewed away and back again by a calculated amount, and then following the instructions on the hand control, I adjusted the latitude silver bolts only to recenter the star in the centre of the field. The processes is then repeated for the little azimuth bolts on the side of the head. However this made my error worse in the RA axis, but slightly better in the DEC. I ended up manually polar aligning again twice, but my error was still way out from what it usually is, so I don’t know what was happening there.

I decided to see if it found M31 using the GoTo hand controller; it found it straight away and put the core of the galaxy bang in the middle of my screen on a 30 second test exposure. Luckily there was no star trailing or elongated stars, so I decided not to push my luck, and kept it at 30-seconds. I did have to manually re-frame the image though by using the controller, just to get M110 and M32 in the image. It was a slow process, with only being able to use test exposures, but I eventually got there. To help with framing, I also had to rotate my camera slightly, putting the galaxy diagonally corner-to-corner to fit it all in. It’s that large!

I ended up doing five batches of 60x 30-second exposures, giving me a total of 2 hours 30 minutes. However, I suffered the same problem with light pollution that I faced with the Triangulum Galaxy. However, Andromeda is that much brighter than the Triangulum, so I was luckily able to use all the data. Even so, I think a light pollution filter is in order in the coming months.

Post processing was inevitably more difficult, trying to counteract the light pollution, while still pulling through all the detail. I ended up processing this one twice in photoshop, as I wasn’t happy with my original edit. Also looking round the edges of the image, its got clear amounts of comatic aberration. I’ve noticed this in a few of my images, but luckily I’ve managed to crop most of it out until now. However, I think it’s time I rectify the problem at the source, and get the Baader Coma Corrector for my DSLR, especially if I want to start doing wide-field subjects.

M31 – Andromeda Galaxy

I really hope I get the chance to go to a dark sky site in the autumn and I can get the chance to re-do this amazing galaxy. Even if I could go to a Bortle 5 site, the exposure time would be dramatically reduced compared with my back garden, to get the same amount of detail.

As it looks at the moment though, that was the last of the clear skies for another fortnight here in the UK. Someone somewhere must have bought a new telescope! Oh well!

Till then, clear skies!

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