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Re: [ATM] Finder

Richard F.L.R. Snashall wrote:
> Updating a design that uses two OTS lenses:
>
>     http://users.rcn.com/rflrs/Ptz07-15x.len
>
> It still needs a larger eyepiece to give the full field.
> I found ER52 on the Anttlers site, but also:
>
>     http://users.rcn.com/rflrs/leyep/erf01-02x.len
Great... if it ever got there.  The problem is that when
the telescope and eyepiece are set up this way, the outer
light cone is diverging away from the axis; it never hits
the eyepiece.  I could not come up with a solution without
adding another lens:

Title: Ptz07-15w
48.8 mm f/5.998 Refractor with 36 mm Erfle eyepiece
Field: 8.20 Degrees
Sugg: MG LDX189 and LPX259
Sugg: MG LDX145(2) and LPX249

Surf    Radius   Thickness    Glass   Diameter

 STO  Infinity   -2.303521                48.8
   2    130.38           8    N-BK7       50.8
   3   -130.38       0.341                50.8
   4   -130.38           3     N-F2       50.8
   5  Infinity     184.085                50.8
   6    91.814         6.6    N-BK7       50.8
   7  Infinity      30.266                50.8
   8   -91.814           3   N-BAK2       39.2
   9    130.38    54.97938                39.2
  10  Infinity    9.737931            42.35049
  11    77.038        11.5    N-BK7       50.8
  12   -77.038           3    N-SF1       50.8
  13    77.038        11.5    N-BK7       50.8
  14   -77.038         0.1                50.8
  15  Infinity         7.2    N-BK7       50.8
  16   -79.053        8.45                50.8
  17     41.57        14.4  N-LAF34         42
  18    -41.57           3    N-SF1         42
  19     255.8    21.73176                  42
 IMA  Infinity                        8.048307

Even then, the last doublet no longer has matching OTS
surfaces.

The AFOV is about 70 degrees.  Some of the outer cones still
miss the eyepiece.  With 1 mm radius allowed for mounting,
vignetting starts at about 3.6 degrees (of 4.2) and reduces
the throughput by about 27% at the field edge.

The exit pupil is about 6.1 mm.  The image surface here is
set up for the minimal diameter for the whole the field of
view. This is quite a bit larger the exit pupil diameter; I
don't have a feel for how good or bad this really is.
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