Hi Rod
TK-68 is a very old cerium - I'm not sure if its available any more. I used to use it - don't remeber it being particularly aggressive. if your surface doesn't clean up to a nice sphere quickly maybe your pitch is too hard and you are not pressing enough . I always use polishers on the soft side and get nice smooth zone free surfaces cold pressing fairly regularly. What kind of pitch are you using ?
Mark
Quote:
Originally Posted by Rod
I am working on a long focus 6 inch mirror for a schiefspiegler. RC is 200 inches approx.
After a lot of trouble with all kinds of zones I have a rough hyperbola, looks like an f6 parabola. I am hoping that will be relatively easy to reduce to a sphere.
I am finding the long focus sphere a bit more of a challenge than I expected but it is interesting and I like being able to use the ronchi test as a null test.
Does anyone know anything about a polishing compound called TK 68?
I was given a jar of it by a friend who used to make optics professionally and have used it for polishing this mirror. I read a vague reference to it elsewhere being an aggressive polishing compound in which case it sounds unsuitable for finishing a mirror like this. I have some red rouge so could switch to that.
Rod.
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