Re: 2" 90° Apparent Field Eyepieces Announced

From: Richard (rander3127_at_rogers.com)
Date: 07/02/04 

Date: 2 Jul 2004 14:45:31 -0700

brianc1959@aol.com (brian) wrote in message news:<3c459ba.0407020607.68f2eaba@posting.google.com>...
> shneor@my-deja.com (Shneor Sherman) wrote in message news:<9dedb1fb.0406300643.2e10efd6@posting.google.com>...
> > jonisaacs@aol.com (Jon Isaacs) wrote in message news:<20040629175818.11708.00000633@mb-m11.aol.com>...
> > > >My experience with Burgess has been excellent value for the money. But
> > > >I do wonder about the optical characteristics of this eyepiece.
> > > >
> > > >Clear skies,
> > > >Shneor Sherman
> > >
> > > Probably best to take the wait and see attitude if something isn't currently
> > > yet available. Burgess Optical has been somewhat optimistic in the past about
> > > delivery dates...
> > >
> > > Jon
> >
> > Here's some more info from Bill Burgess: It's a 7-element design, all
> > ED glass,"broadband multicoatings on all air-to-glass surfaces", and
> > pinpoint stars to the edge down to f/3.5. Availability is at least 60
> > days out.
> >
> > The part about pinpoint stars to the edge of a 90° apparent field 29mm
> > eyepiece sounds very attractive. Maybe some of our eyepiece design
> > mavens can tell us why this is either impossible or comes at the price
> > of field curvature, loss of contrast or some other desirable optical
> > characteristic. Or not.
> >
> > Clear skies,
> > Shneor Sherman
>
>
> Don Dilworth demonstrated that its possible to build a 90deg. eyepiece
> with extraordinary performance. See U.S. Patent 4,720,183. The
> designs published in this patent are among the highest performance
> eyepieces I've ever seen. Much better than even the published Nagler
> designs. No ED or high-index lanthanum type glasses are needed. The
> only drawback is size. A 29mm focal length would have some elements
> as large as 4" in diameter. Below is the patent prescription for a
> 15.9mm Dilworth:
>
> Surf Radius Thickness Glass Diameter
> OBJ Infinity Infinity 0
> STO Infinity 16.367 3.984463
> 2 -46.13459 1.294 1.805180,25.430 34
> 3 59.64817 12.152 1.638540,55.420 39
> 4 -25.6419 0.4099999 39
> 5 104.509 14.0534 1.620410,60.320 60
> 6 -57.40218 24.826 60
> 7 50.58608 12.4375 1.620410,60.320 62
> 8 4353.534 0.4099999 62
> 9 23.4904 10.75047 1.620410,60.320 45.2
> 10 26.7368 11.6589 40
> 11 -83.8454 3.57986 1.620040,36.370 40
> 12 23.38768 14.06033 32
> 13 33.9786 5.868849 1.846660,23.830 33
> 14 221.1201 4.122499 33
> 15 -46.2614 3.39373 1.539960,59.710 33
> 16 56.31179 -27.43597 33
> IMA Infinity 28.58338
>
>
>
>
> Brian
> www.caldwellphotographic.com

Big waste of time, size and money when ED glasses can be bought now.
I can just see those poor refractor and Newtonian owners trying to balance
that thing, once they had a 4" focuser that is.
-Rich
-Rich

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    (sci.astro.amateur)