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ZEISS DTI thermal imaging cameras. For more discoveries at night, and during the day.

Recent content by dahyon

  1. dahyon

    Comparing reflector vs Refractor digiscope image quality

    Hello Rodney Have you seen George Raiche's site: http://www.digibird.com/primerdir/primer0.htm He has an excel spreadsheet which is excellent for theoretical/practical digiscoping rigs. It is in fact the originator of Jay Turberville's calculator Some of his added information is particularly...
  2. dahyon

    Comparing reflector vs Refractor digiscope image quality

    Hello Rodney Your wish list of requirements can be plugged into this calculator: http://www.jayandwanda.com/digiscope/digiscope_calc.html I have had go and it seems you would need 8000+mm 35mm equivalent focal length in order to achieve an image filling the proportion of the frame you have...
  3. dahyon

    Scopetronix MaxView Eyepiece 40mm

    Hello Gene The Maxview 40mm thread is a "T" that is 42x0.75 metric. David
  4. dahyon

    Help on this one please ? Sheffield UK

    I spy with my big yellow eye...
  5. dahyon

    Stars and Moon images with 450d

    Have a look at this site of Jerry Lodriguss, it shows you what is possible with a wide range of equipment, the moon section has a table for various exposure situations: http://www.astropix.com/HTML/I_ASTROP/TOC_AP.HTM Here is an image of the milky way from a 135mm lens on an equatorial mount...
  6. dahyon

    Dragonfly for ID - Bucharest, Romania

    Hello Cristian I think it may be a male ruddy darter(Sympetrum sanguineum). It has a red clubbed abdomen, all black legs, small yellow area at base of hindwing and the number of cell rows below radial supplemental vein look right. A head on image would show the extent on black on the frons which...
  7. dahyon

    Testing prime focus digiscoping setups

    Hello Paul I use the ClarkVision chart in tandem with slant edge analysis, mainly because I find it more intuitive to visualise than abstract shapes. What I had in mind for you was this kind of chart (see attached - reduced for web) which tests the whole image frame both for resolution and for...
  8. dahyon

    Testing prime focus digiscoping setups

    Good morning all I now understand that some of you are striving to develop a qualitative test chart for relative comparison of astro-scopes. I know that there has been a lot of time invested in developing the ISO 12233 chart here in this group but this chart was designed for scientific...
  9. dahyon

    Testing prime focus digiscoping setups

    Good morning Jules You are of course entitled to your opinion. Do others agree? For myself I am only trying to help clarify some misunderstandings on test chart measurement. For instance the ISO chart 12233 being used in your protocol has a maximum resolution of 2000 lw/ph but the Canon 450D...
  10. dahyon

    Testing prime focus digiscoping setups

    Jules I can't simplify that output because I do not have the original files. To illustrate: I have taken the ISO12233 image from the DPReview test of the Canon450D and analysed it with Imatest and present a simplified summary output showing change of resolution across the frame the change in...
  11. dahyon

    Testing prime focus digiscoping setups

    Hello Jules Your test target is of course based on the ISO 12233 standard which requires that the active chart area (20cm 35.6cm) had to fill the full frame of the camera's ccd sensor using the framing arrows provided. The points I made still apply to your target. I have taken the liberty of...
  12. dahyon

    Testing prime focus digiscoping setups

    All of the tests reported in this thread have ignored a fundamental parameter necessary for any meaningful interpretation of test chart results. The easiest way to explain is to refer to the 'Koren 2003' target because this has been explained in detail on Norman Koren's site; before his...
  13. dahyon

    question about ideal match of eyepiece magnification and scope

    The brightness of an image depends upon a number of factors: • Magnification applied to the image at the eyepiece; • Intensity/quality of the light coming from the object being viewed • Diameter size of the telescope objective as a light gathering lens. • The type and quality of glass used for...
  14. dahyon

    Some digiscoping experiments with a dslr

    In response to Jules's question why is there a difference between the metering of the P5100 and the Canon 20D when using a pentax 80X21mm Baader eyepiece: The answer is that the exit pupil of the scope is the same for both but this light cone then has to cover quite different sizes of ccd. I...
  15. dahyon

    Help make Adaptor

    Hello David Here is a composite image showing the rig. This is a very cheap and cheerful arrangement. When electrical tape is used to fix the stepdown filter to the eyepiece is remains quite secure, the camera can be unscrewed leaving the stepdown filter in situ and one has full use of the...
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