Sunday, 22 November 2020

Drizzle Fish

 Drizzle Fish

Recently I took the opportunity to take advantage of around 4 hours of clear sky here in Herefordshire.  I didn't have much planning time, so I opted to revisit a target I first imaged back in December 2019.  This was back when I just started using my Altair Quadband filter and I was sticking religiously to a tried and tested processing workflow in PixInsight.  As well as learning a bit more about the filter and processing, there has also been one other big step forwards with my data collection.  In my last few outings, I have started using the drizzle feature in SharpCap pro.  In my traditional way of imaging using SharpCap, I couldn't drizzle as the feature is only available when using the Live Stack feature.  However, I read that you could get around this by simply saving each of the subframes by clicking on a tick box in the Live Stack feature.  This sorted the sub frame saving issue which meant that I could then utilise drizzle when guiding.  I'll post more on the technique and settings I use another time, but for now, let's take a look at the results.
The two images below are cropped around the main part of the target showing a good proportion of the nebula itself, but also so well defined background.


The first image is quite noisy throughout the colour and background.  You can also just about make out that there seems to be a pattern where the noise appears to run diagonally top left to bottom right down the image.


The second image is part of my most recent image.  It shows the same cropped area, but notice the significant reduction in noise between the images.  While this is undoubtedly partly down to improved processing, the use of drizzling during the data gathering phase has made a huge difference, completely removing the diagonal noise patterns throughout the image.

IC1795 - The Fish Head Nebula

Having taken that big step forward and produced notable improvements, I shall undoubtedly drizzle on all my deep sky imaging from now on.  This only leaves me one thing left, and that's to show off the finished final image.  I seem to have a little problem with sensor noise coming through on the right side of the image.  A new dark library would of probably sorted that out.  Nevertheless, I'm still very pleased with this drizzled quiet fish head.



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