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face of the correction plate inside tube

cassegrain catadioptric Celestron Meade SCT
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#1 Julian Sanz

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Posted 27 March 2020 - 01:39 AM

Good morning, I have some questions.. :
  How do you know what the face  of the correction plate (lx200gps 10") is, what goes inside the tube?

I've read that if you run your finger nail through it, it looks rougher... but I notice it anyway...

 

Thanks


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#2 davidc135

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Posted 27 March 2020 - 03:13 AM

It shouldn't make any difference which face is in or out. Meade makes, or used to, each face the same dividing the correction between the two sides.

It's not possible to tell if a surface has been aspherised by touch but you could try interference using a prism face, for example, and a fluorescent light source. Or any piece of glass with a reasonably flat surface, an uncoated diagonal.

 

David


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#3 davidc135

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Posted 27 March 2020 - 03:19 AM

P2231009.JPG

 

Above is a semi diameter of a corrector plate I've been working on showing contact interference fringes with a 4 inch flat. The sharp change in direction around the neutral zone which is often at either the .71 radius or .87 radius position is the giveaway.

 

David


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