[ATM] Spherical F1-2 Correction for Parabalization

["Jeremy Batterson" <jdbaterson@msn.com>]

Yes, I see, so someone would have to develop a CCD which understood directionality of incoming light. My friend Hughes is right now polishing a 16"F-2.4, which he's never attempted before, and thinks he won't have too hard a time with parabalization. I am doubtful. This makes me wonder about techniques. How about a fresnel corrector-lens? This would have to be high-grade, with millions of grooves, I think, instead of the crude types that are usual. Perhaps such a lens could be custom-fabricated for a particular F-ratio. I think that the technology could be developed to shift the angle of ingraining of the groves, at different distances from the center of the diffraction lens, as well, to cause particular correcting effects. It might be easier to produce a custom-made corrector than an optical one, once this technology is developed. The thought is to figure some way around the difficult task of parabalizing an F1 - F2 ranged surface, since it is not hard to produce these surfaces as perfect spherical surfaces, but difficult to parabalize them. Other than that, we discussed the old dry paper polishing method, which used to be common, whether this might be helpful for rough polishing. 
  ----- Original Message ----- 
  From: Chuck Taylor<mailto:chucktaylor@speakeasy.net> 
  To: Jeremy Batterson<mailto:jdbaterson@msn.com> 
  Cc: atm@atmlist.net<mailto:atm@atmlist.net> 
  Sent: Saturday, January 01, 2005 9:41 PM
  Subject: Re: [ATM] Batterson address change


  >II) For those who want to produce F2 or F1 mirrors, the only problem is >parabolization, which is very difficult at such ratios. In these days of >computerized corrections, what of a CCD which takes the image from a perfect >spherical F1 or F2 mirror and corrects for aberration?  Thus, the hard part could >perhaps be circumvented. Would this be possible?

  The problem is that the ccd has no way of knowing which part of the 
  light came from which part of the lens. So the computer program could 
  not know which way to move it and how far to create the correction required.

  This is very different than optical correction because in optics, that 
  knowledge is retained --- a parracor in effect not only receives the 
  light, but distinguishes where it came from by the angle it arrives at. 
  A parracor or other optical corrector then reacts differently to the 
  light depending on the angle the light strikes the corrector. A ccd does 
  not and therefore does not retain that information, information that is 
  needed to make the correction in the proposed computer program.
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