ATM I started the mirror grinding

[Alvaro Cortizo <alvaro@netpandora.com>]

Hello List!
    I  started  with  chordal  strokes  last night. I worked for about
    2:45hs,  total,  grinding  with  chordal  strokes  and  #80  grit,
    washing, measuring sagitta every 3 or 4 wets, etc, so far the deep
    on  the center of the mirror is 0.042", about half what i need for
    my  8" F6 mirror (and yes, id know that i dont need to measure the
    saggita  so  often  yet,  but  id  like  to "see" how the glass is
    developing, i cant believe how the sphere is making alone!.
    The  carburundum  make  loud  noise  for  a complete turn (4 times
    rotating  about  1/4  turn  each),  after that (about 1:30min) the
    noise  is  a  lot softer, the noise is pretty different at what is
    heard         on         the        stellafane        video
    (http://www.stellafane.net:90/images/atm/img_mirror_ref/chordal.wmv)
    On  the  video  is  a  pretty  high frequency noise, mine is a lot
    deeper, lower frewuency,  i  dont know if its because on Stellafane
    they use a tile tool, and im using a glass tool.
    Also,  sometimes  i  see  "sparks"  through the mirror while i was
    grinding,  i  presume  they  where small glass pieces that get out
    from  the  edge of the glass, because that make small strikes over
    the glass... they dissapears on the next wet, anyway.
    
-- 
Best regards,
 Alvaro
Rosario, SF, Argentina