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michael.h.f.wilkinson

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About michael.h.f.wilkinson

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    http://www.cs.rug.nl/~michael

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  1. I also have an older Carl Zeiss 85 mm F/1.4 (Contax mount), but to date have had better results with the Sigma
  2. The thing is that especially for those CMOS sensors optimized for planetary imaging, read noise is so low it hardly affects the image. Other sources are orders of magnitude larger, especially sky background in Bortle 4 or 5 skies (that is considerably larger than even the dark current in my non-cooled ASI183MC). Back to the original image: Really nice result, inspitrational, even. I am now curious what my ASI183MC with Optolong L-eNhance filter might do combined with my Sigma 50-100mm F/1.8 zoom, which really surprised me in its performance at F/1.8 on comet NEOWISE. Even with the larger sensor of the EOS 80D stars were pretty good in the corners. Might be worth having a go.
  3. Glad the issue was resolved. As far as I know these are made by Vixen, and look identical to the Vixen ARK 20x80mm bins of a former PhD student of mine. I also briefly had the 16x80 version, but the maximum IPD was 72 mm which was just shy of my 73 mm IPD. I didn't notice this in the 20x80s, which gave beautiful sharp images, but with the larger exit pupil of the 16x80s it was a bit of an issue. I now have the Helios LightQuest 16x80, which go to 74 mm IPD, so I have room to spare.
  4. There are wider ones. The TMB Paragon 40mm had 68 deg FOV (clones are the TS Paragon and the Skywatcher Aero). There is also the Meade S5000 40mm SWA (or its MaxVision/ES clones) at 68 deg FOV. I have a Vixen LVW 42 at 65 deg FOV, and the Panoptic 41 mm is also 68 deg. These offer the widest true FOV in a 2" barrel EP. this is why 50 mm EPs generally have a smaller apparent FOV. If you can get your hands on a TMB Paragon 40mm I would pounce on it, as it is very good, comparatively light, and extremely comfortable.
  5. Finally got round to processing the other batch of data I got on September 19. This concerned 302 30s exposures with the modded Canon 550D and 200 mm F/2.8 L lens stopped down with a step-down ring to F/3.5 on my EQ3-2 mount. This was clicking away with an interval timer while my ASI183MC was gathering M27 data on the Meade SN6. I stacked the results in APP, and tweaked a little bit in Gimp. No filters used, and focus was apparently nudged slightly off, which caused red halos round stars. Still, I am quite happy how much detail was captured in the nebula itself, given my Bortle 4-5 skies. Should try this combination again, and lock focus properly.
  6. +1 for the ASI224MC. I had a lot of fun with it. I now have the ASI183MC, which handles both planetary and DSO imaging well, but that is considerably more expensive
  7. That is superb. Should really get myself a C11 or similar scope
  8. I have heard of that option, will try to locate it. Given the nature of the data, I could simply combine the blue and green channels for O[III] (with a little H-beta in there maybe) and use the red as H-alpha. I doubt restacking the ton of images with channels separated would show much difference in the data
  9. Couldn't resist having a bit of a tweak to my previous M27 effort. I felt H-alpha was being drowned out by O[III], and as these data were shot through an Optolong L-eNhance filter with an OSC camera, the only option was to tweak curves with Gimp. Previously, I had only boosted the red channel, but wasn't quite satisfied. I therefore reigned in blue and green, only at the higher levels, and feel the result is better balanced. It seems to have removed much of the cyan cast of the stars as well. I also cropped some of the artefacts left by FITSwork's unsharp masking routine. A bit of the H-alpha in the outer shells is coming through, but data are needed, although that doesn't seem likely in the coming week at least. Star colours could also be improved by added unfiltered colour data (prefereably from a dark site). Whatever the shortcomings, I am very pleased with this first real attempt at M27. The previous version was this:
  10. Replace the legs with wooden ones. I did that on an EQ1 tripod, and now have something quite sturdy: I now use it with my P-mount
  11. Lovely image. The result of an epic journey into astrophotography
  12. Having cylindrical astigmatism, I have to wear glasses, and many modern EPs have 16mm or more eye relief, which I have found sufficient for my needs, although 18-20mm is ideal. Longer focal lengths are generally OK, as even the Plossl or Ortho designs have generous eye relief at long focal lengths. The main issue for wide-field observing with the C9.25 (likewise for my C8) is the limitation posed by the 1.25" visual back. This means either a 32 mm Plossl or 24 mm super wide angle (like the MaxVision 24mm 68 deg EPs) give you the maximal field of view. Going to even longer focal lengths gives nothing in terms of FOV. There are two ways around this: If the scope is not an Edge HD type, get the 0.63x focal reducer and insert it between the scope and the visual back. They pop up second hand for little and extend the FOV by 1.58x linearly (or 2.5x in terms of surface area on the sky). This should work well with all your existing kit. The other alternative is to get a 2" visual back, along with a 2" star diagonal, and 2" EPs. More expensive, but certainly worthwhile, I have found. I should add I happily used the focal reducer method for years, it is just that once I needed a 2" visual back for my Vixen flip-mirror, I got lured down the path of 2" EPs.
  13. If you can have a go at the Saturn Nebula (NGC 7009). I once had a look at this one through Olly's 20" Dob (Sir Isaac), and the vivid blue-green colour was just amazing
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