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Re: [ATM] Figuring question
At 2006-05-31 10:42 -0400, lance clarke wrote:
>Here are the numbers:
>
>zone radius reading
>1 1.032 0.006
>2 2.225 0.029
>3 2.844 0.043
>4 3.574 0.071
>5 3.990 0.079
>6 4.505 0.095
>7 4.863 0.106
>8 5.271 0.123
>9 5.600 0.132
>10 5.939 0.144
>
>All numbers are in inches, I'm using a slitless tester, and the readings
>were using 2 masks to measure every second zone. I do my analysis with
>Figure XP, and find that I have a low zone at zone 7, followed by the
>outermost zone being too high.
Sixtests agrees with Figure XP (as always), zone 7's deviation relative to
RMS-minimizing parabola (R = 3149.891 mm) is -20 nm and the edge is ~+50
nm. Also, the RMS surface error is only 17.5 nm (±2.5 nm, assuming
readings are ±0.002") = 0.852 Strehl. It's good enough unless you are a
perfectionist, in which case you want to proceed VERY carefully - no
overshooting. I agree with Mike Lockwood, it's probably easiest to move
toward a slightly shorter parabola, R = 3149.791, for which you have a +60
nm high center, implying one of Texereau's "deepening the center" strokes,
but only a couple of minutes before testing again to see if you've gotten
the Strehl up to the pefectionist's level.
-- Jim Burrows
-- mailto://burrjaw@earthlink.net
-- http://home.earthlink.net/~burrjaw
-- Seattle N47.4723 W122.3662 (WGS84)
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