Re: [ATM] Stubborn Oblate Spheroid.. update

[Guy Brandenburg <gfbrandenburg@yahoo.com>]

I am positive that Peter is mistaken. You do indeed
have TDE, not TUE. The easiest solution for that is to
take VERY short strokes for a good long time. Press of
course, and check again about every half hour.
Otherwise, the overall figure looks nice and smooth.
The oblateness gets fixed later, once the TDE is
fixed.
Guy

--- Peter <Peter@kitgear.com> wrote:

> 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/
> >
> >
> >
> 
> _______________________________________________
> ATM mailing list http://www.atmlist.net/
> 
> _______________________________________________
> ATM mailing list http://www.atmlist.net/
> 


Guy  Brandenburg
Washington, DC
My home page:
http://home.earthlink.net/~gfbranden/GFB_Home_Page.html
_______________________________________________
ATM mailing list http://www.atmlist.net/