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About ollypenrice

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  • Birthday 12/02/53

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    Imaging, Cycling, Thinking, Literature, French culture, Mountains...
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    South east France, Lat 44.19N.
  1. Brought my first scope!

    Take a flat block of wood and four six inch nails. Knock in two of the nails next to each other at an angle to each other so that, seen from in front, they make an X shape. The top half of the X makes a V. If the collimator body is about 6 cm long knock in a second 'x' shaped pair of nails a bit less than 6cm from the first pair. You have now made a perfectly workable pair of vee blocks. Place your collimator in the vee blocks and shine it at a distant wall, say in the longest room of your house. Rotate the collimator in the vee blocks and observe the point of laser light hitting the wall. As you rotate, does it remain a point or describe a circle? If it describes a circle it's out and needs collimating till it describes a point. The longer the room, the more accurate the test! Olly
  2. M33

    A maddening problem and I'm sorry you have it! Pre and post flip is irrelevant unless the flip dislodged the guilty particle(s). (When you do a flip the entire light path is inverted so the same flats apply.) I wonder if something wandered into the light path between the imaging run and the the blue flat? If so, just try a different flat (lum?) on your blue set. You know the look of the artefact so try different flats/no flats till you get the best result per channel. There's a formula out there on the net for calculating the distance of the offending particle from the chip but I have never used it. Is the particle on a filter or on the chip window? And is it mobile? I don't know. I do know that I'd attack this one in Photoshop with some hope of fixing it. Olly
  3. IC63 HaRGB

    I think it's up to the imager. Personally I try to remove glows and flares from sources off shot but I wouldn't make a virtue of this decision. (Sometimes they are worse when the star is off shot. Paul Kummer and I had no bother with Deneb on the Deneb panel of our NAN mosaic but two adjacent panels had flares. They'd look a bit bizarre appearing out of nowhere so we Photoshopped them.) Olly
  4. M33

    I really like most of this image but what's going on with the brown patch lower left in the disk? Just to its right there's a similar shaped magenta patch suggestive of artefact. Ha does bring out some nice features if not overdone. Olly Edit. Sorry, I missed Wim's similar observation.
  5. I'm Very Confused

    Yes, but the mount looks overloaded so don't expect perfection. Olly
  6. NGC 7635 and M52

    I thnk the overall reds were a bit high so I like Alacant"s adjustment. Good image ether way. Olly
  7. Iris Nebula - Where did I go wrong ?

    You originally asked what you were doing wrong and John, who knows what he's talking about, (see his images!) said, 'nothing.' He was right! Processing is a never-ending learning process. The opportunity to learn will literally never end. Olly
  8. I'm Very Confused

    The whole point of autoguiders is that they do reduce periodic error. They give real time updates on where the mount is really pointing and send corrections to the mount to go back to the originally chosen position. How well they do this depends on a number of things but the underlying accuracy of the mount is not usually the most important of these things. Backlash in the gears and the sensitivity of the motors to guide commands are usually more important. Even with an autoguider the difference in performance between 'premium' and 'basic' mounts is considerable, though not anything like as considerable as the difference in their prices! Olly
  9. Focal Reducers

    'The greater advantage is that the reducer drops the effective f/ ratio, and can cut photographic exposure time by half or more.' Be warned, this is a deadly subject and a matter of much dispute. Eek!! Very obviously, since the reducer does not increase the aperture, it cannot increase the number of photons from 'an area of interest' which lands on the chip anyway. We've talked this one to death on the forum so I won't rehearse it again here but try Stan Moore's famous article which also appears in Rob Gendler's AP book, Lessons from the Masters. http://www.stanmooreastro.com/f_ratio_myth.htm ' I've viewed with and without the reducer in my C6, using both 1.25 and 2" back and EP's. The FOV is substantially larger with the reducer in place, especially when shooting prime. I am unable to get the entire disc of the Sun or full Moon in the camera's FOV without the reducer in place.' In this sentence you're doing two things, 'viewing' and 'shooting,' which are not at all equivalent. The FOV when 'shooting' can be, and probably will be, limited by the size of your chip. Your eye admits of a larger field of view and, on top of that, you can move your head and peer into the field stop of the EP, something which the chip cannot do. The reducer will certainly increase the FOV on your chip. No problem there. It's perfectly possible that you can get a wider FOV with your present EP and reducer but I believe I'm correct in saying that, eventually, the reducer cannot increase the visual FOV over the maximum allowed by a 2 inch EP unreduced. The baffle tube is the ultimate arbiter in my understanding. We need the SCT expert, Peter Drew, to settle the matter! Olly
  10. Focal Reducers

    I did once try my 35 Panoptic in a 10 inch SCT reduced to F6.3 and found it rather unpleasant around the edges. I hadn't, at that time, sussed out that it wouldn't widen my FOV because of the baffle tube but it wasn't very nice optically anyway. I think you'll be about at the field limit without reducer. Someone will be able to give accurate figures, I'm sure. Olly
  11. Andromeda Galaxy with IFN

    That's an interesting one! Good to see a new take on M31. Olly
  12. Focal Reducers

    Their drawback in SCTs is that they don't allow for a wider field than can be obtained with a 2 inch visual back and widefiled 2 inch EP. The baffle tube is the impediment to going wider still. Olly
  13. Iris Nebula - Where did I go wrong ?

    I'll PM you to avoid thread derailment. Olly
  14. For imagng I don't think the FS60 is as good as it should be but it is very crisp visually. Olly
  15. Iris Nebula - Where did I go wrong ?

    No, I've always been open minded on CMOS and, so far, this is only available in OSC. 36 meg and full frame has to tempt any FSQ owner. Mono would be perfect! Olly