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Re: [ATM] Luri-Houghton prescriptions.
Bob May wrote:
>I've been playing with the Lurie-Houghton prescription on the two
>lenses and seem to find that the equal radius pairs of curves
>doesn't seem to do the best job. The equal radius curves seem to
>do some inverse coma along with more astigmatism than doing
>different radius curves for each surface.
>What I've come up with is the following set of curves for the
>typically specified lens set:
>Object
>0 12.5
>Refraction
>BK7 0 -96.3
>Refraction
>Air -0.81 275.9
>Refraction
>BK7 -0.96 96.3
>Refraction
>Air 1.457 -275.9
>Mirror
>-61. 119 0 13
>FocalPlane
>-1.69403
>WAVELENGTH
>0.643 0.54 0.486
>
>
Using F, e, and C (weights 0.5, 1.0, and 0.5, respectively),
I get something like:
Surf Radius Thickness Glass Diameter
OBJ Infinity Infinity 0
STO Infinity -0.2073462 12.5
2 94.3 1.25 N-BK7 13
3 -177.3 0.12 13
4 -94.3 0.91 N-BK7 13
5 177.3 61 13
6 -119 -59.3622 MIRROR 13.97398
IMA -110.0207 1.500112
This assumes about 0.01" separation at the edge and roughly
equal minimum thickness for the two lenses (c. 14% of
semi-diameter).
>the format is in Dave Rowe's TRACE program where the first number
>is the distance and the second is the ROC of the surface.
>The first data set gives a spot size of 0.00024" in diameter
>
>
Comes out to be about 0.00020" in the field center (I used spot
size optimization.).
>while the second gives a spot size of 0.00012" in diameter. The
>images of the spots on the first show that the off-axis spot has
>a bit of inverse coma and the size of the spot is about twice the
>size of the second set of spot diagrams where the way off-axis
>spot shows a nice oval which indicates only astigmatism.
>Any comments? I've got a guy that is about to build the scope
>and I'd want to make sure that he builds the best possible.
>
>
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