Monday, September 29, 2008

The Double Cluster

I finally splashed out on a Canon 20D from eBay to upgrade from my 10D - something I have been pondering over for a while now. Why? Well, the CCD is quite a step quieter than that of the 10D, there are obviously more pixels, and the price was pretty good as well! As much as I'd love to buy a new top of the range camera, for my astronomical needs it's not the best return on investment as the 20D upgrade.

Anyway, I set up in the back garden with just my trusty f/1.8 Canon 50mm lens mounted on a Vixen mount for tracking. I had just finished building a long exposure cable (parallel port to cable release) so my laptop can queue up a sequence of shots whilst I go indoors and keep warm, so I used that to capture 10 60 second frames of the Double Cluster in Perseus - spurred on after hearing a talk at the Bristol Astronomical Society about it. The quarter moon was not far away and raised the background level tremendously, but I could still cut through enough of it to capture the cluster.

I'm rather pleased with the results to be honest. Considering I was pushing it with ISO1600, the noise was relatively low - a lot lower than I would have got on the 10D at any rate.

What I didn't realise was that I'd actually captured the faintest of glimpses of IC 1805 and 1848 - slightly better known as the Heart and Soul nebula. It's really faint, and you can only just see it if your monitor is calibrated correctly, but it is definitely there! Here's an annotated version to show it better along with a few other surprise visitors in the frame! - Note: It appears that Blogger has re-compressed the JPG's after uploading, and the Heart and Soul nebulae are even harder to spot than before :(

The 20D (and other EOS Canon models) all have the intrinsic problem of the internal IR filter cut off curve being somewhat broad, causing hydrogen alpha to be clipped by well over 50% I believe. One day I may pluck up the guts to modify it and replace with a more forgiving IR filter, but that's for another day! Until then, these lovely hydrogen alpha clouds are going to remain a little elusive to me!

Some people say that imaging is not "true" astronomy, but I learn more about the night sky from my own adventures in astrophotography that I do from any book or magazine. The realisation of just how faint some things are and how big or small they are from a picture give much more understanding and weight than just a hard magnitude or arcsecond number - or at least it does for me! I like to think of it as Practical Learning :) I certainly would not have though to go looking for the other Stock clusters if it wasn't for capturing then whilst imaging something completly different .... nothing beats the knowledge that you have captured photons from far away places, travelling for more years than one cares to imagine, and have preserved their legacy for ever more in a photograph hanging on your wall.


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