Re: [ATM] Not tde or tue, important oblate spheroid, ellipsoid

["Jerry" <wa4guu@verizon.net>]

Ok Lütfü

That smoothed out rather well. Trimming the lap is probably what helped it
get smoother. That is a hill. The edge looks good.

The hill shouldn't take long to take down and I would say that you may as
well do some normal MOT big W parabolizing stroke as illustrated is most all
ATM books.

Are you familiar with that stroke?

15 minutes, maybe 20 minutes if you stroke as slow as I recommend. Resist
the temptation to do too much work at once. You will probably need more work
than that but you need to test and see that the curve is going the way you
want it to. If it is not going right you will want to know before you go too
far. You can adjust the stroke by what you see happening on the surface.

The normal MOT parabolizing stroke almost always works the center faster
than the outer zones. If that is the way it works this time it might just
take care of the hill and get you on your way to a smooth parabola. 

I'm still a bit worried about whether the pitch lap will last until you are
finished. The smoothness of your surface now gives some hope it will last
long enough if you do not make any figuring errors on the way to the
parabola. Unfortunately that is almost never the case on a first mirror.
Maybe this time.

Be sure to trim any pinches in the channels. In figuring you do not want the
lap to start behaving badly because it can mess up a good curve and surface
smoothness.

Press well, stroke slow. 

How many lines per inch (or mm) on your grating?


Jerry



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