I would like to build a Schlieren photography system with a single mirror setup*. My question is - what type of mirror (parabolic/spherical) is good or at least feasible for this setup?
The theory says that spherical mirror is the right choice since a point source is needed to be focused back to a point at similar position. However, parabolic mirrors are easier to find and get and some people seem to use them. My question is - what conditions need to be met so that a parabolic mirror is sufficient? I'm loking for data - focal lengths, mirror diameters, etc. Personal experience counts.
Thanks for any answers.
*light from a point source goes through the tested area onto a mirror, is reflected, goes through the tested area again, is focused into to a single point where there is a knife edge and then ends up in camera