Hello:
I may have an opportunity to focault test a large and fast mirror. Suffice it to say, it's larger than 1 meter and faster than f/4. Now, I have a little focault testing experience on the kind of mirrors amateurs more commonly come across, but nothing like this. Making such a large Couder screen is cumbersome, so we may do the focault test photographically and fit the null zones in image processing. Thus, instead of moving the knift edge to put the null at a certain radius, we'll find what radius the null is at for a given knife edge position. So my questions are:
1) Does anyone out there in astromart land have experience focault testing such fast mirrors?
2) Are there any particular "gotchas" or things to look out for?
3) Are there any special considerations is making and using the focault tester?
4) What kind of light source do you use? A slit, pin hole, fiber optic?
5) Any other adivse that's helpful?
Thank you
Cheers
Mike Connelley
I may have an opportunity to focault test a large and fast mirror. Suffice it to say, it's larger than 1 meter and faster than f/4. Now, I have a little focault testing experience on the kind of mirrors amateurs more commonly come across, but nothing like this. Making such a large Couder screen is cumbersome, so we may do the focault test photographically and fit the null zones in image processing. Thus, instead of moving the knift edge to put the null at a certain radius, we'll find what radius the null is at for a given knife edge position. So my questions are:
1) Does anyone out there in astromart land have experience focault testing such fast mirrors?
2) Are there any particular "gotchas" or things to look out for?
3) Are there any special considerations is making and using the focault tester?
4) What kind of light source do you use? A slit, pin hole, fiber optic?
5) Any other adivse that's helpful?
Thank you
Cheers
Mike Connelley
