Primary mirror is held vertically and tested in a “Double Pass” method with a optical flat. Complementary tests with eyepiece to ensure a stigmatic surface. To obtain surface accuracy the knife edge is moved along the optical axis with a micrometer set at zero at the mirrors image centre and moved to its edge zone. This recorded a value in the double pass system of 0.0082”. The surface smoothness is obtained by sampling measurements across the surface. This raw data is introduced into a “Zemax” optical design program which calculates the Peak to Valley best fit fringes, Root Mean Square and Strehl factor.

The smoothness of the surface is demonstrated by the straightness of the Ronchi lines and Contrast pictures below.

            RONCHIGRAM                        CONTRAST

Listing of Zernike Fringe Coefficient Data

File : C:\

 Title: SAMPLE

Date : TUE AUG 12 2003

Using Zernike Fringe polynomials.

Field                                        : 0.0000 in

Wavelength                              : 0.5500 microns

Peak to Valley                          : 0.089107 waves

RMS (to chief)                         : 0.036105 waves

RMS (to centroid)                    : 0.036105 waves

Variance                                  : 0.000689 waves squared

Strehl Ratio                              : 0.948537

OLDHAM OPTICAL UK

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NORTH YORKSHIRE, YO11 2RL, UK.

TEL / FAX (0) 1723 506050

Email <sales@oldham-optical.co.uk>

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