NGC 7822 - First Time
Greetings and welcome. If you have stumbled across this blog post, or indeed this whole blog site, then you're either in search of astronomy pictures and shenanigans, or you've fallen asleep face first on top of your keyboard while Google or some other search engine was open on your screen and you've weirdly ended up here. Whichever it is, again, welcome!
This post is about my most recent image taken from my home observatory here in Herefordshire. It's a first for me, taking an image of NGC 7822. It's an emission nebula in the constellation of Cepheus, one of the great Autumn constellations for us astronomisers in the northern hemisphere. Before I get on to writing about this particular image, you may ask (especially if you are new to the whole astronomy and astrophotography thing) how did I stumble across this target in the first place? Well, the quick and simple answer is, books. But not just any old star atlas or reference book. I'd like to give a shout out to two books in particular that I use to decide what I'm going to try and image at ant given time.
The first is the popular 'The 100 Best Astrophotography Targets' by Ruben Kier. I'd say that this is almost essential when first starting out in the hobby. It contains images of the targets mentioned and describes how best to image and process them. At the end of the day though, it is only 100 targets, so by the time you look at the specific time of year you are imaging, you can rule out a healthy chunk of the year. Then your given location on the globe will also mean you rule out another chunk, so you quickly end up with a limited choice.
Recently though, I've bought a new book called 'The Astrophotography Sky Atlas' by Charles Bracken. While it doesn't have all the pretty pictures the the first book has, what it does contain is a great cross section of catalogued targets and their locations. Over 2000 targets in total! They're also arranged in order of the best time of year to image them. The other good thing with this book is that the positions are also marked up on a full set of star maps. And it is without this book, that I would probably never have stumbled across, or at least considered imaging, NGC 7822.
Anyway, back to it. Back on 26th October, I rolled back the observatory roof and started my most recent imaging run. NGC 7822 was an ideal target, rich in Oiii and HA in particular, along with Sii for good measure, it makes a good target for OSC imaging techniques, especially when using a tri or quad band filter. It remains high in the sky for a great portion of the night at this time of year so was a no brainer. The acquisition of the data went well. Guiding went well and focus held pretty good for the whole evening. It was only after stacking the final data I noticed all was not entirely well, but I haven't managed to suss out what was amiss.
On the full sized image, I've got a strip anomaly that I can't work out. I pretty sure it's not light ingress into the imaging train, but I've picked something up somewhere. Anyone have any clues. Here's an uncropped version of the image, complete with anomaly.
What's annoying is that I think this target has so much more to offer. It's surround by clouds of gas and nebulosity which really add to the image and could be enhanced further during processing. But having the brighter strip down the right side sticks out really badly. To salvage the image, I ended up cropping it to frame just the target itself, cutting out the grey/green stripe.
Finally to round off, the other thing I'm not entirely happy with on this image are the brightest of stars and their halos. I appreciate it's a limitation of the type of refractor I am using, but I have just found out about Seti Astro's tool called Halo B Gone! I think I will be having a bit of a play with that in the near future! Until next time, clear skies!
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