Re: [ATM] Ants of the World -- Unite!

["Richard F.L.R. Snashall" <rflrs@rcn.com>]

Richard F.L.R. Snashall wrote:

>
> A two mirror system with a field flattener to utilize this
> chip might be (400 mm f/10):
>
On the other hand, you could move the primary mirror to
achieve the focus, perhaps putting the focus behind the
primary, worst case configuration (the near focus), or using
a tertiary mirror to put the focus outside in the worst case
configuration (the far focus).  Flex would still be used
to modify the conic of the primary as it is moved.

I reoptimized for that method and ended up with:

    http://users.rcn.com/rflrs/frc1-12f.atm
    http://users.rcn.com/rflrs/frc1-12f.len
    http://users.rcn.com/rflrs/frc1-12f.txt
    http://users.rcn.com/rflrs/frc1-12f.zmx

but used 10 m for the intermediate distance:

    http://users.rcn.com/rflrs/frc1-12m.atm
    http://users.rcn.com/rflrs/frc1-12m.len
    http://users.rcn.com/rflrs/frc1-12m.txt
    http://users.rcn.com/rflrs/frc1-12m.zmx

while still using 5 m for the near distance:

    http://users.rcn.com/rflrs/frc1-12n.atm
    http://users.rcn.com/rflrs/frc1-12n.len
    http://users.rcn.com/rflrs/frc1-12n.txt
    http://users.rcn.com/rflrs/frc1-12n.zmx

This change in middle distance becomes a little more obvious
with an overlayed drawing of the three configurations (drawing
the focal plane behind the primary):

    http://users.rcn.com/rflrs/frc1-12.jpg

The advantages of using primary motion to focus:

    a) The net motion is only about 190 mm.

       Secondary motion requires about 310 mm to cover the
       same range of object distances.

    b) Performance improves.

       This method has a design visual Strehl of 0.986 over
       focus and field.  You could actually tell if the ant
       had recent cosmetic surgery!;-)

    c) Mechanics might be easier.

       All focal changes affect only the primary.

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