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cfpendock

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Everything posted by cfpendock

  1. cfpendock

    Tadpoles in Ha

    From the album: DSO

  2. cfpendock

    Cone in Ha

    From the album: DSO

  3. cfpendock

    Pacman HaRGB

    From the album: DSO

  4. Thanks Rob. Exactly what I always thought. In fact I have often regarded the RGB part of the image as merely providing a colour "wash", rather like the tinting of black and white photographs before the days of colour. But it doesn't explain the RRGB method described by Robert Gendler, particularly his comparative images of the horsehead in LRGB and RRGB. Except that his RRGB image took nearly twice as much time, presumably because the extra time was just using the red filter? And no clear filter used for this? chris
  5. I like the reference by Brantuk of the article by Robert Gendler. The explanations for LRGB and HaRGB are clear but I'm not sure about the RRGB. Does it mean that one should obtain high resolution images using the red filter, and then use this instead of a clear IR filter for the luminance channel? Chris
  6. cfpendock

    NGC 3718

    From the album: DSO

    This is too faint and small (8mins) for my sky. 16x5mins LRGB, CPC1100, Atik 4000. But good to get Hickson 56 group of galaxies at the top - 450 million light years distant.
  7. cfpendock

    M88

    From the album: DSO

    This target is VERY small - just 7 minutes across. Needs more time.
  8. cfpendock

    M13

    From the album: DSO

    8x30 secs + 8x90 secs RGB, no luminance
  9. cfpendock

    horsey1

    From the album: DSO

  10. Actually, this will make a fine reference image for anyone interested in this bit of the sky. Amazing. And what a lot going on! Chris
  11. cfpendock

    Bubble in HaRGB

    From the album: DSO

  12. cfpendock

    Heart HaRGB

    From the album: DSO

  13. cfpendock

    Comets

  14. cfpendock

    18minslovejoy

    From the album: Comets

    Comet Lovejoy, January 2014
  15. cfpendock

    heart

    From the album: DSO

    7nm Ha - 14 exposures, each of 20 minutes using 385mm focal length.
  16. I think that although the field rotation will be the same at the pole as on the equator (the angular rate will be the same), the actual length of any star trails will of course increase at the equator. My problem with understanding the equation comes from the definition of "maximum allowable misalignment". A sort of combination of negatives.....You are right - it is difficult to visualise! Chris
  17. Thanks for pointing that out, Mark. You are correct, of course. I cannot explain why, but the equation comes from a paper by Frank Barret: http://celestialwonders.com/articles/polaralignment/PolarAlignmentAccuracy.pdf. Can you explain it? Chris
  18. When guiding, as Mark says, in some areas of the sky (close to polaris), I find that polar alignment is much less critical. There is an equation which might be interesting for you. It indicates the accuracy required, depending on where you are looking in the sky: E = (4500 x S x cosD) / (T x F x A) Where : E is the maximum allowable polar misalignment in arcseconds S is the worst case length of star trails (in microns) D is the declination of the target in degrees T is the exposure time in minutes F is the focal length in mm A is the angle between the guide star and the target in degrees Chris
  19. From the album: DSO

    20 x 20 minutes in Ha. 4" refractor and Atik 4000.
  20. cfpendock

    M31 wide

    From the album: DSO

    M31, 4"refractor with reducer, 10 x 300 seconds in each of LRGB. Cropped because of poor flats.
  21. cfpendock

    Jellyfish

    From the album: DSO

    4" refractor with reducer. RGB 12 x 120 seconds each, binned 2 x 2. L 12 X 120 seconds unbinned. Ha 9 x 1200 seconds. Rubbish flats, poor Ha blending. Gradient.
  22. cfpendock

    Rosette

    From the album: DSO

    4' refractor with reducer, 4 x 300 seconds each RGB, R blended with 6 x 1200 second Ha. Rubbish flats. Too pink.
  23. cfpendock

    M51

    From the album: DSO

    M51. CPC1100HD unguided. 4 x 120 seconds each RGB binned 2x2, 4 x 250 seconds unbinned L. Streetlights.
  24. I think that is a really good shot. The actual nebula can be seen a long way out from the core, which itself is not overblown. I was surprised that you achieved this from exposures of 80 seconds only, rather than a mix of different exposures (shorter for the core and longer for the wispy bits). Perhaps it is down to expert processing? Chris
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