Re: ATM Caustic Zone Length

["Rodger Petersen" <faintfuzzy@worldnet.att.net>]

Hi John
I'm also a newbie, on my 4th mirror. My first episode in parabolization
will shortly be coming out as a movie starring Bill Murray... or Chevy
Chase, naw too good looking. In retrospect it was funny, I kept
overcorrecting , 4 times. The best advice I can give is press a lot, short
sessions, test a lot. I mean a really short session, say 1 minute.My F
ratio was 9.5 on a 6 inch so it was close as a sphere. The F5 I recently
completed only took 12 minutes of actual figuring.
Keep on testing
Rodg

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> From: John H. Svensson <ic089@cleveland.Freenet.Edu>
> To: atm@shore.net
> Subject: ATM Caustic Zone Length
> Date: Thursday, July 03, 1997 5:12 AM
> 
> Pardon the newbie question which follows but to clear uo/p a seeming
> discrepancy for others who may just be getting started on their first
mirror:
> Someone on the list referred to Berry's recommended "72 strokes" to 
> parabolize from a sphere, Tex states it's about an hour's job on an 8",
> certainly more than 72 strokes even at a moderate 25 per minute rate. 
Who's
> right here, or at least who is closer to the mark for the average
polisher?
> I ask because I'm using Tex and set off on about 2 , 10minute "classis/c
> stroke" sessions expecting it to be about 45 minutes to be close for a
6",
> my central ray to marginal ray focus images don't seem to be coming down
> toward my theoretical .09 inch caustic zone.  Have I inadvertently gone
> hyperbolic? TIA.  
> jhs