M51 – Whirlpool Galaxy

It’s been another cloudy fortnight here in the UK. I haven’t been able to get out at all to do any imaging, but luckily the weather has cleared this past weekend.

I’ve been holding off on this target, as it’s probably my favourite galaxy and wanted to do it justice. I wanted to wait until I have an astro-modified or a dedicated astrophotography camera, allowing me to get the red specs of Hydrogen Alpha emissions across the disc surface. However, the viewing this past weekend was crystal clear and I couldn’t pass up the opportunity to photograph this incredible pirouetting galaxy pair.

M51, located around 23 million light-years away from Earth, is actually two galaxies that have collided. The larger galaxy, M51a is slowly consuming the smaller one, M51b. This famous interaction can be easily seen in my image, with a blue finger stretching out from the main spiral and wrapping around the golden ball.

Since the summer solstice, the evenings have slowly been drawing in. Last time I had chance to image, I couldn’t polar align until 11PM. However, it’s starting to quickly get dark around 10PM, so on Sunday I started setting up at around 9:30PM to be ready for when darkness fell. I levelled off the tripod using a bubble level that I use for my turntable. A bit unconventional I know, but it’s a larger version of what is on the head of the EQ5 Pro. I can place it inside the tripod and it clearly shows if it’s level or not. I continued with the setting up and re-balanced the whole set up. It’s best to balance the system slightly heavy on the east side, allowing the gears to have constant contact inside the mount.

I’m getting better with balancing in both the Declination and Right Ascension axis’s. Dylan O’Donell does an excellent video on how to balance your telescope. Polar alignment is still a little bit tricky though, but I was fully polar aligned and 3-star aligned in under 30 minutes, with error in both axis’s under 1 arc-minute. I’m getting quicker!

My Polar Scope – Put in backwards at the factory!

As you can see from my polar scope, Polaris is perfectly placed at 10:54. This is where my PolarAlign app on my phone showed me where Polaris should be placed in my reticule.

Now some keen-eyed viewers would see that my reticule is flipped round! And yes, that is true. It must have been put in the wrong way in the factory. Luckily, this doesn’t matter too much with this type of reticule, as it’s simply a clock face. As long as the 0 and 9 are vertical, I can polar align properly.

I started with a few test shots, just to see if I was on the right target, and to see how long my exposures should be. I settled on my seemingly standard 30-second exposures at ISO800. I tried a 60-second exposure, but my stars were starting to become elongated, so I defaulted back to 30-seconds.

Doing a bit of research today, ISO800 is the perfect ISO for my Canon 600D. It’s the highest ISO that gives the largest amount of dynamic range, with the least amount of noise. Luckily, it was quite a chilly night so thermal noise was reduced enough to be sorted afterwards in post processing.

I decided on an imaging plan that consisted of batches of 30-minutes, just incase my camera decided to crash on me again! I leave a 2-second gap between each image to allow it to save to the SD card. Doing batches also allowed me to check on my images throughout the night. As it turns out, the galaxy stayed rock solid in the middle of the frame from batch to batch. It only moved less than 20 pixels from the first shot at 11AM, to the last shot at 1:50AM. I’m happy with that!

I firstly did a total of 2 hours imaging, taking me upto about 1:30AM. I decided to do another 20 minutes of images, as I know I caught a few satellites or airplanes passing through a couple of my exposures. Of course, I caught another couple during those extra minutes. This left me a total exposure time of 2 hours 19 minutes.

At this point, I had already planned to do 1 hours worth on the Triangulum Galaxy, just below Andromeda. However, facing east is looking directly over the Black Country conurbation. As could be seen from my previous post, the whole area looks like an orange bubble of light pollution that stretches from north to south. Just one hour wasn’t enough to get any useful data though, and so it was abandoned in the post processing stage. I want to come back to this target, but maybe when I’m at a darker location.

At 3AM in the morning, I did a half hour of dark frames and took 60 bias frames, finally getting into bed around 4AM. The sky was starting to become light and a few Noctilucent Clouds were visible, but I was just utterly shattered at this point, so I didn’t get a chance to take any photos.

Post editing was a dream though, and I think it has produced my best Astrophotography image to date!

M51 – Whirlpool Galaxy (Tagged with http://nova.astrometry.net)

Luckily the following night was also clear, so you can read about that in my next post in the next few days!

Till then, clear skies!

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