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