Re: [ATM] Stubborn Oblate Spheroid.. update

["Peter" <Peter@kitgear.com>]

Jason,

Your edge is slightly turned up NOT down. It will likely correct itself once
you parabolize. Again don't worry so much about the oblate because you can
parabolize perfectly from this stage. Just make sure the mirror is polished
out fully at the edge.

Peter

-----Original Message-----
From: atm-bounces@atmlist.net [mailto:atm-bounces@atmlist.net]On Behalf
Of Jason Hissong
Sent: Saturday, September 17, 2005 12:00 AM
To: atm@atmlist.net
Subject: Re: [ATM] Stubborn Oblate Spheroid.. update


Thanks for that info Mike!  Your site is excellent.

Update:
After about 2 hours of polishing with MOT, shorter strokes or about 1.5
to 2" (to avoid TDE) and slight side to side Ws, I get this:
http://www.undermidnight.com/images/atm/oblate_spheroid_4.jpg (inside
the ROC)
http://www.undermidnight.com/images/atm/oblate_spheroid_5_oroc.jpg
(outside ROC)


It seems that the center of the mirror is getting pretty spherical while
the edge seems to be slightly turned down.  Is it my imagination or is
the turned down point getting closer to the edge? (if so.. yay!)  I will
continue this path for one or two more hours to see how it goes.  I
think I am about an hour or two away from a complete polish.  I find it
difficult to use the laser test with a BVC blank because of the layers
reflecting back various things.  I cannot tell sometimes if it is the
layer underneath or the top.  Because this mirror is a 4.3, in the
center, the second layer is close.

I have discovered another way to see how well the surface is polishing
and that is during my ronchi testing, I will look at the mirror a slight
angle away from the light reflecting straight back into my eye.  When
the edges were full of pits, those pits show a great deal (like a fuzzy
green haze wherever those pits were).  Now I don't see anything
reflecting off of the mirror except for various particles like hair,
incompleting rinsing marks from tap water (using distilled water
virtually elimates these markings).  Don't know if that is an adequate
test or not.  I know it is really bright!

Thanks for all your help...  this one has been a pleasure to work.  Of
course, that may change when I head onto figuring! :)

Jason Hissong


Mike Lockwood wrote:

>Hi,
>
>I have posted a short page about oblate spheres with a picture of how
>I have seen them form, and why a TDE usually results.
>
>http://bi-staff.beckman.uiuc.edu/~melockwo/mirror_making/oblate/oblate.html
>
>	Mike Lockwood
>
>_______________________________________________
>ATM mailing list http://www.atmlist.net/
>
>
>

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