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derrickf

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    http://www.dfarley.co.uk

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  1. It's been a few years since I processed an image but I've recently started to re-learn what little I used to know about astro image processing. Big thank you to the team for making this high quality dataset available to us, the high SNR of the data makes a big difference to the processing choices available. The image was processed in PI then saved as a 32 bit TIF which was then saved as a JPG from Affinity Photo (no other processing was undertaken in Affinity). The main processing steps in PI were: RGB channel combination Photometric colour calibration Noise reduction (TGV denoise & MMT) Stretch to non-linear Noise reduction of L channel (TGV Denoise & MMT) Mild Sharpening with LMT Stretch to non Linear Sharpening with HDMRT LRGB Combination Star reduction (using Adam Block method) Colour saturation and Intensity tweaking using Curves Transformation Save as 32 bit TIF for transport to Affinity Photo from which it was saved in JPG format for submission here. I'll probably take another shot at it to see if I can recover more of the star colour
  2. I would really appreciate the link to the .STP files too. You have done a fantastic job with this design Derrick
  3. I'm confused about what you mean by this statement about a lack of accuracy. I use an Atik EFW-2 and Atik OAG combo imaging at 2400mm FL and a pixel scale of 0.45 arc seconds per pixel and get a routine guiding performance of less than 0.2 arc seconds RMS. What have I misunderstood about your issue? Derrick
  4. The Atik OAG works fine for me with EFW-2 and Atik 383. In response to your earlier question about finding guidestars - I have never failed to find a usable guide star in my Lodestar2 FOV when guiding my 12" RC. HTH Derrick
  5. That sounds like a really useful script - do you plan to make it available when it is finished? Derrick
  6. I don't believe these are diffraction spikes caused by obstructions (normally secondary supports etc.) but are probably artefacts produced, when imaging at fast focal ratio, with CCDs fabricated with micro-lenses over the pixels. This was a hot topic in the SBIG forums several years when the ST-10XE (non-micro-lensed) was superseded by the ST-10XME (micro-lensed). Many people who rushed to replace their ST-10XE with an ST-10XME, because of its significantly better QE due to the micro-lenses, could not understand why they were suddenly seeing "diffraction spikes", often only vertically, in images made with fast refractors. It was eventually shown that the effect was only observed at fast f-ratios. The horizontal artefacts on the bright stars are probably caused by the pinching effect described by Ollie. HTH Derrick
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