Re: [ATM] Fixing Tom's oblate sphere

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

Hello Tom

IF the mirror were fully polished...

Look at the 5 line outside Ronchis. You can see what has been happening. 

The 4-2 Ronchi shows raised intermediate zone (the wide hill with the hole
in the center). And TDE.

The 4-4 Ronchi shows less raised intermediate zone. And slightly less TDE.

The 4-5 Ronchi shows raised intermediate zone has become more of a raised
center and the hole that was in the center of the wide hill, has
disappeared. The mirror looks to be more oblate. The curve is a smoother
oblate. And the TDE may be worse.

That would seem to mean that while you have been wearing the hill down you
have also been wearing away the intermediate zone at least as fast and it
looks a bit faster than the center. So the oblate is worse but the hole has
been removed. You needed to get the hole out and that is how you do it. You
remove out side of the hole. But it would be nice to wear the entire hill,
but fastest at the center and slow at the base of the hill. With the smooth
oblate that you have now, the base of the hill would be at the mirror's
edge. Wearing the center fastest would be MOT. This would shorten the radius
of curve at the center to come to match the short radius of the outer zone. 

A TOT alternative wears the outer zone to a longer radius to match the
longer radius of the raised center. And the idea here would be to find the
stroke to wear the edge the fastest and dropping to slowest at he mirror's
center. You find the right length stroke, this will fix the edge too.

The oblate shape suggests scaling up the size of your W. Say 5 inch stroke
length and a 4 inch wide W. that would be 2 inches to each side.

If it were me, I would pick one or the other... either MOT or TOT and stick
to it for a while. There are a couple of reasons I can think of. If you do
more than one thing at a time, when something works, you won't know what
component of your various strokes did the deed. One of those may be taking
the TDE out, and the other putting it back in. One could be working
perfectly and you wouldn't know.

That the center wasn't polihed would suggest that you should use MOT. But
the TDE might best be worked TOT. 

You could go different ways here. The key is whether it is fully polished.


Jerry

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