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Last Updated
03/31/2019
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Detailed entries for one subject from the INDEX TO HOW TO DO IT INFORMATION. |
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TELESCOPE MIRROR TESTING xx TELESCOPE MIRROR xx TELESCOPE TESTING Test your telescope's optics. How to use a star at night (or an easy-to-build artificial star) to evaluate the performance of your telescope. How to grind, polish and test an aluminum mirror. Mirror making class at Macalester College (St.Paul, Minn.) uses four specific goals to assure that students are successful in grinding a usable telescope mirror. The goals are described and the results of various Foucault tests are illustrated, along with the corrective action necessary. How to make a pinhole light source for use with the Foucault test. The light source uses a single fiber from a fiber-optic bundle. Description of an "almost" null test for parabolic and ellipsoidal mirrors. Includes a chart of minimum separation of mirror and knife-edge for various diameter mirrors (7.5 cm to 30 cm). A simple test to determine if a telescope mirror has been fully polished prior to aluminizing. Also includes a tip on elutriating or washing polishing rouge. The volume method for determining the radius of curvature of a deep concave lens or mirror, without need for a precision spherometer. How to make precision pinholes for use in pinhole cameras, testing telescope mirrors, etc. An improved method over the Foucault test shows the actual profile of a mirror's surface. Requires only the standard knife-edge tester. A null test for Cassegrain secondaries. Standardizing the Ronchi test pattern. Point-diffraction interferometry made easy. How to make and use the point-diffraction interferometer (PDI) to test mirrors, lenses and other optical systems. Foucault tester features a digital readout of the knife-edge's position accurate to 0.001". Analyzing a Foucault test. A computer program, written in BASIC, converts your zonal knife-edge measurements into actual highs and lows on the glass surface and deduces the "wavefront error". Mirror testing for non-opticians. How to construct and use a Foucault tester based on the pantograph principle. This allows ultrafine motions of the knife-edge to be measured on an ordinary ruler. Rayleigh water test, a simple way to check diagonal mirrors and optical flats. It utilizes the interference fringes which occur between glass and water. A new Ronchi null test for mirrors. The Terebizh null test utilizes a circular grating that you make yourself. Are today's 10" mirrors any good? Interferometer tests of 10" paraboloidal telescope mirrors from six commercial suppliers. How to inspect the edge of your telescope mirror for chips, pits, scratches, and a "turned-edge" problem. How to mask these defects using black ink. A Monte Carlo approach to the Ronchi test. BASIC computer program to compute a set of templates for various positions of the grating when performing the Ronchi test on a telescope mirror. Setup and complete instructions for reflective null testing of a telescope mirror with the help of its own tube and diagonal. A more accurate knife-edge formula is supplied for the Foucault mirror test. Build your own laser interferometer to test optical lenses and mirrors. Knife-edge testing with a video camera. A video camera and paper masks attached to the screen of a TV (instead of the mirror) are the secret to this multiple-zone Foucault test procedure. The double-pass knife-edge test. Build an improved version of the Foucalt tester which bounces the light off the telescope mirror two (or more) times, thus magnifying any surface errors so they can be measured more easily. Zonal test tolerances. A description of the Lord Rayleigh method of describing mirror resolution and how it may differ from other methods. Stalking the wild paraboloid. Description of graphical method to calculate the way in which a homemade mirror will perform in order to determine if more figuring (parabolizing) is needed. How to make focograms. Focograms are photographs of a mirror being subjected to the Foucault test (knife edge test). Build your own Foucault tester (knife-edge tester) and adjustable mirror stand to hold the mirror being tested. How to perform the wire test method for surface testing and evaluation of large telescope mirrors. It is an alternative to the Foucault test. Description of the Macalester College "Four goal system" for making a first telescope mirror. Includes extensive discussion of a Ronchi-type test, including three pages of photos showing test patterns for various mirrors. A reflecting null test for paraboloids. How to use the Waineo Reflecting Null Test, a version of the Hindle test. Includes diagrams and information on building the test jig. Tip: Use an ordinary Ronchi screen instead of a knife edge when making the Dall null test on a mirror. Making and using a slitless (single-knife) Foucault tester with a movable stage sliding on "Teflon". Foucault knife-edge testing for concave mirrors. Includes a computer program for "reducing" the knife-edge readings to produce an accurate wave rating of the mirror's surface. Tips on using the Texereau zone testing method for checking telescope mirrors. A simple practical light source for the Foucault test. Uses a tiny flashlight bulb powered by two AA batteries. A new test for figuring convex hyperbolic Cassegrain secondaries against their primaries. Testing paraboloidal mirrors. What every telescope maker should know about testing telescope optics. Both the "star test" and the Foucault Test are described. Efficient mirror testing. Topics include: (1) Coarse testing using the Everest shadow test. (2) Figuring: Shadow location. (3) Modified Millies-Lacroix reduction method. (4) K1*K2 method of analyzing a mirror surface. (5) Final testing. Making precision paraboloids is easier with the Ross Null Test. Detailed instruction of a method for null-testing large paraboloidal mirrors. Tip on making a focogram (photograph) of an aluminized mirror in order to reveal information on surface smoothness. Includes information on placement of knife-edge (Foucault) tester, mirror reduction process, Millies-Lacrois graphs, etc. The nuances of optical testing. A thorough overview of the various testing methods employed on telescopes and how to understand and compare the results. A secure mirror holder for workshop testing is made from PVC plastic pipe and some perforated hardboard. Variation on the knife-edge Foucault test uses a red glass filter or red/blue acetate filters. Comments on the accuracy of testing optical systems with a star and Ronchi grating. Computer program written in Turbo Pascal which makes the setup calculations for performing a Ross Null test on a parabolic mirror. Tip on using a glass slide (half covered with candle soot) in place of the knife edge in a Foucault test. | |||||||||
Copyright © by Norman Lathrop Enterprises. All Rights Reserved. No part of this publication may be reproduced, stored in a retrieval system or transmitted, in any form or by any means (electronic, mechanical, print photocopying, recording or otherwise) without the prior expressed permission of Norman Lathrop Enterprises, except as permitted by law. |
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