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warping spherical mirror into a paraboloid?

ATM Mirror Making
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29 replies to this topic

#26 brentelgeuse

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Posted 04 December 2021 - 11:39 AM

Thank you. A very interesting read.

Wow, reading this is a long-term project for me. :D 



#27 Tiraki

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Posted 23 January 2022 - 11:32 PM

This discussion is very interesting to me.  I'm hoping to return to building my 10 inch Yolo design shortly.  The design requires a hyperbolic secondary of about -20 conic, 8 inches dia. and the ROC about 340 inches.  Currently the mirrors are at fine grinding stage.

 

My question is can I keep the figure as spherical and then warp to hyperboloid, all else being equal?  (I am already warping the primary 10 inch to toroid and controlling the secondary adjustments from the primary end.)

 

Regards

Keith, NZ



#28 brentelgeuse

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Posted Yesterday, 06:57 AM

What about warping an inversion of your desired figure during polishing? Then figure to sphere, relax to hyperbolic

Mind you, I have no experience in grinding. There are much greater minds than mine on here though. 


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#29 Tiraki

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Posted Yesterday, 09:33 PM

I've seen the method of warping prior to polishing and that others have mastered it. My setup is to actively control the figures from the eyepiece either mechanically for the primary immediately in front of me, or via stepper motors for the secondary at the other end.

The idea that I'm toying with, from this current discussion, is to pull from the centre of the secondary mirror using differentiated threads on order to create the hyperbolic figure.  Kind of like two bolts head to head with different pitch threads so as to create an ultra fine adjustment.  A disc pressed onto the centre as a wheel for adjustment.

 

Also, I am intrigued about the James Webb space telescope mirror control via activators at certain points behind the hexagon mirrors.  Does anyone know the figure of the mirrors whether they are all spherical and then activated to the required figure for their respective positions?

 

Keith



#30 Oregon-raybender

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Posted Today, 03:11 AM

This will put you to sleep about JW.  Remember JW is for the IR, the optics don't need to of visual quality.

 

 

Starry Nightswaytogo.gif

 

https://wp.optics.ar.../10/for-Jed.pdf

 

https://jwst-docs.st.../jwst-telescope

 

https://www.osapubli...=oft-2006-OFMA2




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