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ollypenrice last won the day on February 16

ollypenrice had the most liked content!

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About ollypenrice

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    Imaging, Cycling, Thinking, Literature, French culture, Mountains...
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    South east France, Lat 44.19N.
  1. ollypenrice

    How to do flats with Samyang 135mm F2

    I think this is the first time I've heard of under-correcting flats. Over-correction comes up quite often and is often associated with not taking darks-for-flats. If your exposures were very short I wonder if the flats were being affected by the shutter wipe? You could try slowing them down by dimming the source. Olly
  2. ollypenrice

    Exposure time

    Planes are very rare for me, satellites fairly common. What's the problem? They are both dead easy to remove. For a severe plane trail you make a stack with all the subs in it and then another with the plane trailed sub excluded. In Ps do an initial levels and curves routine saved as an action to the full set and save. Now open the set with the plane removed and run the action on that set. Paste the original stretch with plane on top and remove the plane trail with the eraser. Flatten and save. This will add no more than three minutes to your processing time. In truth I rarely need to do this and just run 'remove line' in Astro Art on affected subs before stacking them in Sigma mode. I had seen the upturned end of M31 (extreme left hand side in this example) only once in another image and tried several times to capture it. Only when I went to 30 minute luminance subs was I able to detect it. Olly
  3. ollypenrice

    Horsehead Nebula Luminance QHY9

    Very nice deep luminance. This should bag you some rich brown dust when you add the colour. Olly
  4. ollypenrice

    Taking darks - a cautionary tale

    Atik, bless 'em, give you a screw-on metal cap which is absolutely dark and totally effective. Why do I like Atik? That's one reason. Olly
  5. ollypenrice

    Exposure time

    A quick rule of thumb would be to say that fewer-and-longer subs will go deeper and more-but-shorter subs will give a smoother result. I work only by experiment and have found that, with CCD at a dark sight, the very long sub does go deeper. For this reason I often use 30 minute subs in narrowband and, on some targets, in luminance. When trying to find the outer limits of M31 I found a very clear advantage in 30 minute luminance subs over my previous set of 15 minute ones. I actually had less total integration time in the 30 minute set yet it went deeper. Olly
  6. ollypenrice

    Seeing in city vs countryside

    Local heat sources are, indeed, terrible for the seeing. Olly
  7. ollypenrice

    dark-bias-flat subtraction

    You would have a greater choice of software running Windows. If going for a cheap PC don't skimp on USB ports because hubs can be bad news. Olly
  8. ollypenrice

    What binoculars do you need to see Uranus?

    Very good review! I see that Uranus is currently Mag 5.85 which, if true, puts it well within naked eye range for those with good eyesight at a dark site. Olly Edit: this does not include me!!!
  9. ollypenrice

    Strange star elongation issue

    The RASA's weight will not trouble the Mesu in the slightest. I've piled far more weight than that onto mine. If you get your best stars near the zenith then the obvious candidate is mirror flop (an exaggerated term for slight mirror movement.) Clearly, near the zenith the mirror is sitting symmetrically in its cell. It is always risky to guide a reflector with a guidescope because the guidescope cannot see the mirror flop. Neither can the mount, which might be tracking perfectly even unguided. It seems to me that your experiment on the brick wall may not be able to distinguish between various possible sources of flexure. You can put pressure on the scope mounting bar but where, exactly, does that pressure distort the system? I wouldn't like to say. Olly
  10. ollypenrice

    Messier 81 and 82 panorama

    I understand as well but, just as faint signal develops with integration, so does colour. Nobody tells you off for going too deep. Why would they tell you off for capturing too much colour? No, that's a gross over-simplification, of course, but it might make a starting point for a conversation! Olly PS: I just have to add this. With Barry's images you are always left with the feeling that the data had a bit more to give. But I'll bet my bottom dollar it didn't! That feeling of restraint is sooooo important because it leaves you feeling you are looking into space and not at a computer screen.
  11. ollypenrice

    M106 and companions

    Very good and, I'm sure, likely to get even better. Like Barry I feel you'll get more impact with the black point brought in. For information, a deep Ha layer would add some sensational details, not just a 'string of rubies' in the spiral arms but a faint jet or two perpendicular to the disk. These make for a very exciting capture. Olly
  12. ollypenrice

    IFN around M95 & M96?

    Dropbox not playing for me at the moment. Will try later! Olly
  13. ollypenrice

    Leo Triplet (M65, M66, and NGC 3628)

    I can only endorse Barry's comments. A great image, really great, but just a bit 'colour cool.' Olly
  14. ollypenrice

    Leo Triplet

    Deep and sharp. Good job. Olly
  15. ollypenrice

    Oiii flats uneven?

    My flats show little or no difference between filters which is why I often use only luminance flats for all filters. Very occasionally I see a filter-specific dust shadow but it is not more than once per year and often less than that. As Paul says, try the OIII flats. Then try calibrating the set using no flats and then try the Ha flats on the OIII data. See what this tells you. Olly

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