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About SamK

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  1. Talking about 30 years ago, my only claim to (deconvolution) fame is feeling unworthy in undergraduate supervisions with Steve Gull when he wasn't too busy fixing Hubble's blurred images in the early 90s !
  2. Yes, not the Gaussian. It's like the Wavelets filter set to Default, and Wavelet scheme set to Linear, (in Registax Wavelet tab). Yes, of course, it is a problem, but having tried quite a range of planetary stack images - right from Pic du Midi images down to my own (underwhelming) images, and some more in between, a PSF of fairly close to Lorentz (i.e. a Moffat PSF with beta of 1.0) seems to be a very good starting point for all of them. It's only the FWHM pixel width of the PSF that then needs to be guessed. I've tried to incorporate immediate visual feebback in my program in "t
  3. The idea of scaling down an image, applying a transform, then scaling back up again to 100%, and subtracting from the original image, and adding weighted versions of each layer is exactly how Registax wavelets works. The Jupiters below shows the difference images at different scales of 0.5px, 1px, 2px, 4px, 8px and 16px. You just combine some fraction (or none) of each of the six layers to get the repaired image. I know this isn't quite what you are suggesting. It's hard to say what the result would be with your technique without trying it ! What I have found so far is that the stand
  4. A Wiener filter with a very small noise to signal ratio looks exactly like your first diagram. In this case, it's not really a Wiener filter anymore, it's just a simple inverse filter. This would work perfectly to restore a blurred image if there was no noise, but is pretty useless for real images. It's the introduction of an extra NSR factor which changes the shape of the useful repairing Wiener filter. The second plot show a radial version of my original white circle diagrams, showing a typical repairing Wiener Filter. Hopefully you can see the y value of exactly one here for the l
  5. For the Wiener filter row, the "FT of filter" displayed is just the Wiener filter used for the repair, i.e. it shows Wiener Filter as used in the equation: FT(Restored Image) = FT(Input image) x Wiener Filter where the Wiener Filter is a (Fourier Transform) function of the psf. The radius of the white circle changes as you change the FWHM of the point spread function that you use to deconvolve. High frequencies towards the corners are reduced (black), but mid frequencies (white circle) are enhanced, which sharpens as the required scale. The centre, although dark, will be approximat
  6. After many hours of fiddling round with Registax wavelet settings to process my own solar system images, I've always been curious as to how it actually works. In doing so I've put together my own image sharpening program which does something similar to Registax wavelets. For comparison, I've also added some general purpose deconvolution techniques which you'll probably be familiar with from other image processing software (like Wiener inverse filtering, Richardson-Lucy, etc). In choosing a point spread function to deconvolve with, one suprising result was that the typical stack outputs from Au
  7. It is a bonus galaxy, PGC147737, about mag 18. Awesome Horsehead by the way Richard. The framing with the Horse Head dead centre works really well. I like the star spikes and the 3D effect of the dust in the lower half of the frame. The red/blue wispy nebula (IC432) to the left (and slightly up) of the Flame Nebula has come out really well (reminiscent of Running Man). I'm guessing the massive amount of data from 8hrs at f/3.3 has allowed some deconvolution on the brighter details like the Flame Nebula and the blue reflection nebulae.
  8. Hi Brendan If you want to get back to basics, Dave Coffin's dcraw has options to get the underlying ADU values from a RAW image: Using windows command line (with dcraw.exe in C:\temp\dcraw), eg dcraw -D -4 -T "C:\temp\dcraw\file.CR2" The options are: -D Document mode without scaling (totally raw) -4 Linear 16-bit, same as "-6 -W -g 1 1" -T Write TIFF instead of PPM The resulting 16bit tiff produced should will have a maximum ADU value on saturated stars based on the number of bits of your camera, so around 16,000 for a 14bit 450D, 4,000 for
  9. Hi Ciarán With a 60 image stack, drizzle definitely improved stars and brought out a bit more detail out in the nebula (below is Drizzle at 5''/px vs Standard at 10''/px enlarged in Photoshop). I found about 20 images would normally be required to make drizzle work well. I'd guess the main drawback in say 10 images for drizzle is that you'd get a lot more noise than a standard stack and that you'd want to be more careful to get dither working between frames (in PHD). I think you'll be fine with differential flexure (my setup was substantially more botchy than yours). If you do get a
  10. Nice image and setup - Sh2-119 on the left gives a nice balance to the North American and Pelican. I've also found vintage (and budget) M42 prime lenses work pretty well for wide-angle narrowband and give a lot of versatility to an existing telescopic setup. My theory was that with only one wavelength to contend with in narrowband, there's no need to have expensive glass to counter chromatic aberration. A few notes which might help in case anyone else tries this type of setup: +Focussing - With patience, I found I could get good enough focus by hand (I measured FWHM in shor
  11. Here's a close-up of the chain of dark clouds of the Rosette Nebula using public domain data. I've used IPHAS survey H-alpha as luminance with a colour layer derived from the Digitized Sky Survey red/blue channels (transformed to a SHO style turquoise/gold colour layer). My own 8'' GSO RC version (last image below) was the inspiration (shown for low-res comparison). Some people see "animals" formed from the dark clouds... I see a leaping jaguar top right (or spanner!) and an ostrich bottom left. The tiny dark circles to the left of the jaguar's head are referred to as globu
  12. Thanks again Richard, a good selection of targets requiring different processing techniques. My processing was mainly in Photoshop (and by the looks of the Taurus Molecular Cloud, primarily on the saturation slider) ... Cheers, Sam
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