Re: [ATM] A Null Test

[Richard <cnc@cncservo.co.uk>]

Hi Richard,

Monday, September 4, 2006, 5:46:30 AM, you wrote:

RFLRS> It looks like the major gain
RFLRS> here is the second direction reversal in the longitudinal error.

Not sure I understand that Richard.

RFLRS> Interesting test.  The lenses are small and the final cone angle is
RFLRS> also small.  Makes me kind of wonder why someone didn't recommend
RFLRS> that as an alternative (on the "other" list).  Is there any price
RFLRS> to be paid?

It would be interesting to do a thorough tolerance analysis of
both methods. My gut tells me that three lens have more chance
of contributing errors than two, BICBW

I kept the lens parameters fixed and put a V solve on image to
first lens distance, inter lens sparation and second lens to
mirror focal point. I've started making a table, but the
extremes of f/2.4 to f/3.5  and K=-0.8 to K=-1.3 optimised
easily. Worst case null seen was 1/250th wave and typically
better than 1/1000 wave.

RFLRS> I guess an equivalent in the three lens form might be something
RFLRS> like (Isn't green a pretty color?;-):

:)

RFLRS> Was you goal value on RAID zero?

Goal is 0. You need to spread it out to cover the aperture of
the lens. I use four RAID statements, at Py=0.25, 0.5, 0.75 and
1.0 with a target o f0 and a weight of 1. More RAID lines over
smaller dPy increments may help if you have the processing
power. These days I would probably lower that weight a bit.

-- 

Best regards,
  Richard in the UK

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