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Huygens Eyepiece?
Hi all....
Reviewing "Telescope Optics-evaluation and design" the section on eyepieces shows plots and of course the simple Huygens looks absolutely horrendous.....BUT.....when used on a high F ratio (F15) telescope AND allowing the focus/field to be curved you get some VERY nice plots (better than a Nagler at F5) instead.....and the Ramsden shows the same behaviour.... The problem IS is that you can only have a curved field if the focal length of the eyepiece is long enough that your eye can refocus enough to accomodate the curved field.... The authors indicate that a Huygens eyepiece can be used to good advantage if the focal length is roughly a 100 mm or more.... Ive always dreamed of owning a LARGE off axis telescope (and yes I am very familiar with the many designs)....and those designs are typically in the F20 to F30 range if you want a large one without too many mirrors, lenses or non-spherical surfaces.... But the concept of having a scope that was limited to rather high magnifications always bothered me...but then it occured to me that I could use quality commercial eyepieces for the higher powers and one or two homemade Huygens for the low power views.....of course a 100mm Huygen would have a diameter of 4 inches....a 150mm six inches...and a 200mm eight inches! (Al Nagler eat your heart out My question here is....has anyone used a big huygen on a high f ratio scope and how good was/wasnt it? take care Blll |
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