Re: Null corrector for a fast mirror
- John,Last fall, I simulated a point source offset from the OA of a spherical mirror to determine the amount of astigmatism at the offest knife edge of the classic Foucault Test.There was a divergence angle in radians that I put in the setup parameters.I would have to look it up. It required a coordinate break at the mirror.I'll look it up if you wish.Paul
- For a complete solution source anywhere I think the sag at h is needed which can probably be derived from that link. :-) Not sketched anything out so a pure guess. From memory Sixtests allows the mirror to source distance to be specified but that may be just to reduce errors from normal Foucault readings. I don't think it allows offsets to be specified which are another source of error apart from any aberration effects.
Where some views of aberrations go astray is that when a mask is used the aberrations of the whole mirror may not be important. Instead it's the size of the circles of confusion produced by a series of small off axis mirrors in relationship to their diffraction disc size.
I also suspect that there is another test that could be used these days but no sums done to check how large a sensor is needed for good say 1/20 wave results. Hartman, if that is how it's spelled. That one would just involve taking an exposure with the lens off a dslr, moving it a specific distance along the axis of the mirror and taking another.
--- In email@example.com, "Richard F.L.R. Snashall" <rflrs@...> wrote:
> On 5/12/2013 6:06 PM, John wrote:
> > So what is the equation for the exact slope of a conic versus height?