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CN Reports 149 articles

Thermal Modeling and Athermalization in Telesco...
Dec 09 2014  Telescopes are typically stored and operated over a wide range of temperatures. Changing temperatures and extreme temperature ranges affect nearly all materials used in constructing telescopes, as well as the optical properties of the air in the immediate vicinity. This article discusses the two principle effects of temperature on telescope materials: (1) changes in optical and structural material dimensions with temperature, and (2) changes in optical glass refractive index with temperature. These two temperature-dependent material properties usually combine to negatively affect optical performance in refractive and catadioptric systems if not compensated for, and system optimization must account for these properties in the design phase to minimize temperature effects on telescope performance.

User Reviews 1519 articles

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Celestron Ultima 80
Dec 16 2014  I had the opportunity to observe the sky with this spotting scope during my holidays last Summer. My Father in law happened to own the Celestron Ultima 80 for nature watching and shooting sport and had left the scope at his holiday house near the seaside where I spent my holidays with my family. The sky there is pretty good so you can see 5.0-5.5 magnitude stars with the unaided eye at the zenith.

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Nov 23 2006  

What's Up . . . 89 articles

My telescopes—Part 2
Nov 24 2014  

This is the 100th article I have written under the name “What’s Up” for Cloudy Nights and I am now going to call a halt.  It has been fun and I thank all the folks who have sent me messages saying that they enjoy my writing. 

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Small Wonders 32 articles

Apr 05 2011  

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This Month's Skies 123 articles

December Skies
Dec 06 2014  

Highlights: Comet Journal, Martian Landers, Meteor Showers, Winter Solstice, Planet Plotting, December Moon

Focus Constellations: Cassiopeia, Perseus, Taurus, Auriga, Camelopardalis, Lynx, Ursa Major, Ursa Minor, Draco, Cepheus, Lyra, Cygnus, Pegasus, Pisces, Andromeda, Aries

Mike's Corner 6 articles

May 05 2011  

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Uncle Rod's Astro Blog 28 articles

Apr 19 2009  

Fishing for Photons 10 articles

Jul 01 2012  

Binocular Universe 57 articles

Binocular Universe: California Dreamin'
Dec 12 2014  Where has the time gone?  It seems like only yesterday that we were ushering in 2014 and here we are, getting ready to ring it out and welcome in 2015!  Let’s close out the year with a bang.  Go big or go home, they say.  So this month, we are going big!

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