Friday, 12 March 2021

Varying Degrees Of Imaging Success

IC405, Orion and M51

I've been grabbing the imaging opportunities when I can of late.  The weather has been so hit and miss that it was nice to get at least something under my belt.   As I continue my imaging journey, I try to post all my images, and let's face it, a lot of them are rubbish.  Some are results of experiments with processing techniques and others are results are from different capture techniques.  Occasionally, it all comes together in a rather pleasing fashion.
So, I kick this little collection off with an experiment that didn't exactly go wrong, but was an interesting learning curve.  My first image is of the nebula IC405.  I have imaged this target before, but this is the first time I have done so using the quadband filter and the results are not entirely what I expected.  This might be down to poor understanding of the different light wavelengths emitted or reflected by the nebula, or an all out mistake somewhere in my processing workflow.  Whatever the reason, I have really struggled to get any significant colour to the target.
Otherwise know as the Flaming Star nebula, this is a completely different outcome to the last time I tried this.  The last time, I got plenty of blue, violet and red coming through.  This time, just a yellow or orange finish.  I might have to go back and reprocess using a different workflow on this one.

Next, we have an all time Winter favourite for visual observers and astrophotographers alike.  I've had a few goes at imaging the Orion Nebula over the years but as yet have not been able to get an image which I am truly happy with.  The search for the great image still continues.  However, there are mitigating factors for this image.  The thought of imaging in mono intrigues me, but I am firmly in the one shot colour camp at the moment.  And a lot of that has to do with time.  I simply don't have the time to spend taking upwards of 10 hours per image which is often required when using mono cameras.  My general mantra has been to use a capture time with a maximum of 3 hours, and OSC cameras allow me to do that.
With this image of Orion, I reduced that capture time even further producing this image with 6 x 5 minute exposures.  That was down to the great British weather.  The forecast says one thing, but nature decides on taking it's own course.  The tricky thing I find with Orion is producing something which doesn't blow the core of the nebula out.  It's such a bright target (visible to the naked eye under the right conditions) that it's easy to get carried away with getting as much detail as possible with the outer reaches of the nebula, but then lose the structure around the core.  Knowing that the final image was generally quite poor, I tried something a bit different by removing all the stars from the background.  The result, well, it shows some potential and one day I will nail that image of Orion.  Perhaps next Winter instead.

Eventually, when everything comes together I still continue to knock together something I'm genuinely quite pleased with.  M51 is a really pretty target.  A pair of interacting galaxies in the constellation of Canes Venatici and relatively easy to pick up and image with my 80mm refractor, M51 is instantly recognisable.  Other images I have seen of M51 always seem to have a pleasant blend of blues and reds in the arms of the main galaxy structure.  Traditionally, I have struggled to replicate this and I wasn't expecting too much different this time.  I wasn't sure how M51 would look after being imaged with the quadband filter so that was an unknown in itself. 
In the raw data, for some reason many of my subframes seemed to have horizontal banding across them.  I have read forums where other people have had the issue and have struggled to resolve it, but until now, I have never experienced it myself.  I hope that it's transient, one off in nature and doesn't start plaguing my imaging.  
I decided to use a workflow in PixInsight which starts off splitting the stacked image into different (R, G and B) colour channels, carrying out background extraction and then recombining them in slightly different ratios using PixelMath.  Towards the end of that particular workflow, I have learnt some new masking techniques which allows me to really enhance specific colours either just within the target, or the wider background.  
Anyway, 3 hours ish of subframes under near new moon conditions and then another 3 hours of calibration frames and few hours of processing have enabled me to put together this final image.

So there we are for another post.  Thanks for reading and clear skies!

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