On Sunday evening, the clouds finally cleared after an entire week of downpours. Mind you, they took their sweet time to clear as it was nearly 11:30PM before I could even polar align. I could see Vega and Arcturus from about 10:30PM, but Polaris was being shy from behind the clouds.
When it did finally clear, I did my first polar alignment, which to be honest was rather rushed as I’d lost so much time already. I did a two star alignment on Vega and Arcturus, and I chose my target for first light on something simple and well known – Messier 13 – or Great Globular Cluster in Hercules or the Hercules Globular Cluster.
I entered M13 into the go-to handset and watched as it slew to the position it thought M13 was in. If I wasn’t looking through the basic 28mm LET eyepiece that came with my scope at the time, I would have missed it, as it overshot this vague smudge in the night sky.
A quick tip I’ve learnt; if the object isn’t directly where the go-to function says it is, hit esc, and then press and hold escape. It will come up with a screen where you can re-centre the object, and it will re-map the sky accordingly.
In the eyepiece, it’s nothing special. As I said, it’s a very vague smudge, hence why Charles Messier listed M13 in his Messier Catalog, to dissuade other astronomers from mistaking it as a comet.
This globular cluster is 25,000 light-years away and some of the stars are believed to be nearly as old as the universe itself – 12-13 billion years old! From the furthest stars on either side of M13, the estimated distance is about 150 light-years across.
Once I was assured that I had the object in sight, I decided to swap the eyepiece for my Canon 600D DSLR, just for a quick test shot. I wasn’t expecting much. Put the ISO on 6400 and exposed for 30 seconds…
The shot came in and it was completely over exposed, and got some star trailing (need to work on my polar alignment!) but I was in awe! I nearly screamed out loud at 12AM, I was so happy and excited!
So I quickly did a few more test shots to fine-tune ISO and exposure length, and decided on ISO 800 with 60x 15-second exposures, giving a total exposure length of 30 minutes. M13 shifted within my field of view because of inaccuracies in my polar alignment, but it actually worked to my advantage when stacking!
In my haste and excitement, I completely forgot to take darks and flats, so I only had light frames. Note for next time!
This morning, I booted up the old windows laptop that had Deep Sky Stacker installed, and stacked all my images. A few images were cut out of the listing, which reduced the total exposure down to 29 minutes 15 seconds. When stacking, I chose the intersection method, and so all areas that weren’t in every single shot was removed. Therefore M13 is a lot larger in the final image than compared with an individual sub.
The final image was exported and edited in Photoshop CC. A few level adjustments and curves later, this was the end result!
I also uploaded it to a website called Astrometry.net. This site tags your images with star names and other data. I even caught a galaxy, NG6207!!!
I should be able to get multiple nights viewing this week as the weather has turned nice again! So hopefully should be doing a few more posts this week!