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Bob Andersson

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About Bob Andersson

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    UK
  1. Hi Mark, Great catch - thanks for the link. Bob.
  2. Hi Andreas, I believe them to be real but I have significantly enhanced their visibility during processing. I have a feeling that the cause is (supersonic?) shock waves as the Pleiades encounter the gas they now illuminate but my memory might be playing me false. If you Google with that phrase plus Pleiades you should be able to prove me right or wrong. Bob.
  3. Hi folks, Thanks. @Tom - Fair comment. With the lack of deep subs other than the blue ones the best I could do was let the colour wash towards grey for the faint bits. With the limited imaging time the UK weather currently imposes I won't be returning to M45 until next season at the earliest but when I do some deep red (and green) is on the list. Bob.
  4. Hi folks, yarp - yet another re-process. I've come a long way from the original as I've learnt new processing skills. This is from the same data - I hope the result pleases. The Pleiades - M45Bob
  5. Hi folks, Following my discovery of the MaskedStretch script in PixInsight I reprocessed the RGB stars part of my California Nebula data. You can also examine the 4096 x 4096 pixel original here (2.2MB). The California Nebula (NGC 1499) - RGB + HaI'm quite pleased with this one with star shapes and colours better controlled. I hope you approve. Bob.
  6. Hi folks, The California Nebula (NGC 1499) - RGB + Ha 5 x 200 seconds each of RGB plus 8 x 1000 seconds of Ha. TEC 140 + ML16803. The bright star is Menkib (Xi Persei) - quite an interesting object in its own right. Bob.
  7. . Darn it. I can't edit my post to correct the spelling - it should be "Simeis". Somebody has a lot to answer for by forcing the Mods into a policy where someone with 90 posts and a good track record (even if I do say so myself) is treated so rudely.
  8. Hi Tom, The "Sugar Cage" was just my description of how it looked as it crept into my image. Maybe I was feeling hungry! Looking at the FoV of my camera and the coordinates of Seimis 147 (aka Sharpless 2-240 and the Spaghetti Nebula although I prefer my own nickname for it) I think you've nailed it so thank you. I've added it to my own TODO list (one day) and I think the Pentax lens should capture it quite comfortably on one go. Congratulations on your mosaic. Bob.
  9. Thanks folks. Here's a version with a revised colouring for the Ha and with less stars. Bob.
  10. Hi folks, Another reprocess of old data (from last December) to see if my skills have improved. Here's one which includes the Flaming Star nebula, rather deeper than my previous effort: Flaming Star - includes M36, M37, M38, IC 405, IC 410 and IC 417 The full sized 4096 pixel square version is available here (6 MB download) - beware, horrors may await the avid pixel peeper! The challenges for this one were to separate out the faint Ha from some residual sensor noise and to decide how many stars were enough - there were a lot more in the RGB subs. At the image scale offered by the 165mm focal length lens the reflection nebulosity was difficult to extract. I decided where it was by doing a blink comparison of the 1000 second blue stack with the full RGB image (the version with all the stars plus some nebulosity) and then it was a matter of isolating it from the bright stars that were illuminating it. It was added to the Photoshop stack of Ha (no stars) plus RGB (just stars) and the final challenge was deciding how strongly to show it - the reflection nebulosity should certainly be weaker but then it risks geting lost in the artificially strong Ha signal. Something that I didn't find in the original processing of the data last year is the "sugar cage" just creeping in at the bottom of the image at about six-thirty. Has anyone got a shot of the full object? Bob. Shooting Information: 8 x 1000 seconds exposures of Ha 5 x 200 seconds through each of Red, Green and Blue 3 x 1000 seconds through the Blue filter for reflection nebulosity Camera: FLI ML16803 cooled to -25°C. Lens: 165mm focal length f/2.8 Pentax medium format Pointing at: 5h 25m, +34° 30'
  11. Hi Gina, Expensive but I really think the 3nm filter pays for itself. It allows a better S/N ratio for the nebulosity and it also, as you say, cuts down the brightness of the stars in the image. That potentially makes subsequent removal of those stars from the Ha images (my standard workflow) less prone to guesswork although still very time consuming when done manually. Fortunately I can pretty much always get away with an automated star removal procedure plus a little manual clean-up when extracting the stars from RGB data. Here's the conventionally coloured version, the only difference being the Photoshop curve used to colour the Ha data. The Heart Nebula (IC 1805) - H-alpha + RGBUnguided. 8 x 1500 seconds H-alpha + 5 x 200 seconds in each of red, green and blue. TEC 140 plus ML16803. Processed in PI and PS. Stars removed from the H-a image and nebulosity removed from the RGB image to allow separate processing strands. There's a 2048 x 2048 pixel version available here. Bob.
  12. Hi Richard, Thanks for the nice words. Forum policy is what forum policy is so I'll have to live with it as I'm certainly not going to go on a posting spree essentially devoid of content just so I can get back to where I was when I joined the forum not so long ago and was able to edit my posts. I'm much more active over at PAIG now. Bob.
  13. Hi folks, Been a while but I tend not to post here much now as I am not allowed to edit my own posts. My infrequent appearances may possibly be much to everyone's relief after seeing the following image. Here's the Heart Nebula with the hydrogen emission coloured the same as the light I see from a hydrogen discharge tube. The nebulosity was captured using a 3nm H-alpha filter (8 x 1500 seconds) but the physicists tell us that H-beta is always emitted at roughly just over 1/3rd the intensity of H-alpha and the human eye is much more sensitive to H-beta than H-alpha, hence the surprising colour. Regular digital cameras are not a reliable guide to the colour the eye would perceive either as the pigments used, while good enough to extract natural colour information from terrestrial shots, are not so accurate when it comes to H-alpha and H-beta emission lines. RGB stars were extracted from three sets of 5 x 200 second RGB subs. TEC 140 plus ML16803 collected the photons. Bob.
  14. . PP is key provided you have enough image depth to start with. I think your image would benefit from some more processing to reduce the chroma noise. My own tool of choice as a first resort is Topaz Labs DeNoise - if you have Photoshop, Photoshop Elements , PaintShop Pro, Photo Impact or Serif Photo Plus you might like to download the free trial. But yes, more and longer subs, if your setup allows, are the way to go. Great start. Bob.
  15. . And I thought "remote" meant sitting in my nice warm conservatory. My ASA DDM60 Pro mount also benefits from high resolution resolvers: definitely the way to go but darn, such mounts ain't cheap! Bob.
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