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Topics - unoritvie

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Testing large or other optics with long paths through air offers "interesting" challenges due to air stratification, turbulence etc.
The effects of vibration due to wind buffeting, microseisms and traffic all need to be overcome.
Vibration isolation and evacuating the test path are not affordable for most, so other solutions must be sought.
For interferometry, solutions include stirring the air in the path and averaging the results of short exposures that freeze air motion and vibration.
For the various Hartmann test variants, stirring the air to reduce stratification and averaging out vibration and turbulence by using long exposures is effective.
For Foucault testing solutions aren't so clear cut particularly with the zone by zone variants where measurements are made serially rather than in parallel (as in Interferometry and Hartmann testing).

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Eyepieces Questions & Recommendations / Better eyepiece for a cheap scope?
« on: December 28, 2017, 01:04:39 AM »
I'm thinking about replacing the stock 1.25-inch, 20 mm eyepiece of my $129 Orion GoScope refractor with something a little better. My budget is around $100. Does this make any sense? The 80 mm scope has a focal ratio of 4.3. I'm aware of the problems that cheap, fast refractors have. This scope also has a screw-on diagonal, so there's no way to get a better one.

What got me to thinking about this were test reports in which the testers used what they called "their own" eyepieces to improve the view. I'm assuming that "their own" stands for significantly better eyepieces than came with the scope. I would appreciate any insight, even if it's "save your money for a better scope."

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...due to the frustrations of so few decent clear nights to be able to use your stuff?Whether you have a $50 scope or a $20,000 super-duper scope, you can'tdefeat the clouds, haze and fog. It is so aggravating! I must be living in the wrong part of the world to enjoy this hobby very much.
 Where are the best locations in the US for the most frequent clear skies and not a lot of light pollution? Maybe I need to make a move toone of those placeswhen I retire in a couple of years.

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Mounts Questions & Expirience / Friction drives. Potential problems?
« on: December 24, 2017, 03:21:56 PM »
Hi,

I am putting serious thought into purchasing a Mesu Mount 200.  It utilizes friction disk technologies, which I guess from the amount of users that have Mesu's, Fornax's and Gemini's G53F is still not fully understood concerning performance and behaviors with differing geographical locations (climate).

I work remotely (5hrs away) and while Friction Drives seem great on paper, the 1 thing that's preventing me from pulling the trigger is how the mount slides when off balance.  Not so much that I've troubles balancing, however, the idea of slipping.

My observatory is located in a cold, dry and windy climate.  Very cold in the winter (as I write this, it is currently -27*c and also feels just like -36*c down there).  I currently use my CGEM remotely there.  It and all of my other equipment have handled the cold quite well.  On these sharp ultra chilly nights, when seeing is spectacular, the mount has yet to let me down (brief of slewing electricity issues from a 120 cca Deep Cycle Marine battery that's hooked up to a trickle charger).

What happens when it is -30*c and the metal interior contracts?  Is it possible that the coldness can cause a slip and all of my gear smash into my dock, even when the telescope isn't in use?  Or I suppose that could require it to be away balanced?

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Beginners Forum / Learning a new Father/Son Hobby
« on: December 24, 2017, 09:08:18 AM »
Hello all,
I am looking for a book to help my son and I understand the night sky before we make our very first telescope buy.  We are in need of something very basic.  Thanks Beforehand.

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