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An Evolution



Although this has been posted elsewhere I think it might be useful to show how my imaging has (hopefully) improved as I gained experience/equipment.


A Year of DSO Imaging with an Alt/Az

Well, I seem to have attempted my first DSO images in December 15 and January 16 so it's been just over a year of trying to image with the Alt/Az mount. My first DSO target was M42 which I've shared previously but my next target was the Rosette Nebula which I don't think I've shared. I thought it would be nice to see how it progressed over the year.

Image 1: Rosette Nebula through the 9.25SCT using the Canon 60D - no sign of any nebula but look at the resolution of those stars. If you find HD46150, a 6.8 magnitude star that forms the left of the middle pair of stars that make the famous rectangular shape inside the nebula you can see two companions so close they are almost touching. I think this serves as a clear example of why a long focal length SCT is not suited for DSO imaging on an Alt/Az mount!


Image 2: Now with the Esprit 80 with the ZWO 1600MM. I did a terrible job at removing the background and removed most of the nebula in the process (and still left a nasty ring of gradient). Though at least there is nebula to see now! It shows how nice the field of view of the refractor is. Whilst this image has been cropped, it retains probably 90% of the area of a single sub.


Image 3: same data as image 2 but with better processing. I was able to do a better job at removing the gradient and start to bring out some of the detail within the nebula. However, the stars are starting to dominate.


Image 4: my first attempt with a narrow band filter. I love how this image is so much cleaner that an equivalent amount of data collected with the L filter (see above). With very little noticeable gradient this was such as easy image to process.

NGC2239_20161228_v2 1 Ha mono.jpg

Image 5: my first try at adding RGB data to the Ha data in image 4 resulted in an almost monochrome tinted version. I had very little usable RGB and the luminance of the Ha data swamped it, leaving it lacklustre in terms of colour.


Image 6: with a little more data and some helpful processing advice I managed to get a better RGB version. This blends the Ha data into R and L using one of PixInsight's many scripts.

NGC2239_20161228_v2 2 HaRGB.jpg

Image 7: and with an extra 30 minutes data, and further processing improvements. This is back to being a simple HaRGB with the Ha replacing the luminance. Just a small amount of additional RGB data meant I could push it much harder and for it not to be washed out.


It seems 40% of the improvement I've seen over the year is equipment, 40% better processing and only 20% improvement in skill at actual data capture. If you'd asked me at the start of this journey I would have though capturing the data would be the hardest part. It is hard, just not as hard as processing it!

It's also interesting to see how, with each additional dataset, I've had to crop more and more of the image to remove stacking artefacts caused by rotation.

And, to set a baseline for future EQ imaging, here's my current 'best' version of the Rosette. My plan is to start my imaging with this (if the weather improves before it moves out of my viewing range) so I can compare the results.



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