OPO  -  Monitoring the reflectivity and scattering of telescope's coatings



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Science lovers blog


Application notes


These notes are written to help the CT7 user understanding the metrology problems associated with measuring the reflectivity and the scattering of a surface. They sometimes correct approximate or misleading ideas about mirror's coating maintenance . For that purpose, they give precise definition of terms and notions in accordance with scientific knowledge in physics and radiometry.
Application note #11 : Absolute values of reflectivity measurements with a handy CT7a reflectometer

This note discusses how absolute values of the reflectivity of a coated mirror are obtained. For most work, relative measurements seem sufficient in order to monitor the degradation of the coating with exposure and decide when to clean it or replace it. But in some situations, absolute measurements are justified and we give, in this note, the way to achieving it.

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Application note #7 : Measurement of curved mirrors with CT7 and CT7a

This note deals with the sensitivity of reflectivity measurements to the curvature of the measured mirror with CT7 and CT7a .

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Application note #5 : Telescope mirror coating maintenance with CT7

This note is a general discussion of telescope’s coatings maintenance. Scientific, technical and practical rationales are given and amply developed that should clear up some confusions about the subject. The notions of ‘ specular reflectivity ’ and ‘ Total integrated scattering (TIS) ’ are scrutinized. All arguments are grounded on actual measurements on mirrors and on extensive modelization.

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Application note #04 : Basics of straylight definition and measurement

This note had been written to introduce the user of Iris scatterometer to the basic of stray light definition and measurements. The content fully applies to the newest CT7 and CT7a reflectometers / scatterometers . It contains some theory and useful definition of terms. The main part of the note deals with practical matters related to scattering measurement .

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You are perhaps wondering why the application notes have such a bizarre irregular numbering system? We also do. Just kidding, there is a simple explanation: there had indeed been 11 notes published to this day, but the other ones are not relevant anymore, and therefore no more available.

We keep the numbering from the remaining notes unchanged, in order not to create confusion for our long time customers by changing the numbering from the texts they already might have in their possession.





Daniel Malaise worked on numerous ground-breaking astronomy related projects. For example he was in charge of the calibration of the "Celescope" telescope on the very first Orbiting Astronomical Observatory satellite from the NASA. Back in Europe, he took part on various projects from the European Space Agency. He developed, among others, the optical design of the Halley Multicolor Camera . We will upload here interesting insights of some of his most notable contributions.
Astronomy related article #3: Daniel's very first scientific paper


Long before conceiving his first instrument, the very first article published by Daniel was already about comets… When we stumbled across this paper, we found it very interesting to see that Daniel was already considering the idea of “ the launching of a bypassing probe to an active comet ”… in 1963!

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Astronomy related article #2: The first astronomical instrument conceived by Daniel

The first astronomical observation instrument conceived by Daniel was installed at the Haute-Provence Observatory, but little observation time was allowed for comets study. Luckily, Daniel received an offer from the Ondřejov Observatory, near Prague, Czech Republic, to move the instrument there…

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Astronomy related article #1: A two component model of the interstellar absorption

Discovery and description of continuum ultraviolet absorption by non-identified material around several stars. What have we discovered in your opinion?

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« Accurate perception of reality is the condition for rational and successful action. » - Daniel Malaise