I am trying to understand the setup of a Lyot tester and have some basic questions.
So this is a basic article about the Lyot test you probably all have seen who are applying the Lyot test https://adsabs.harva...JBAA..103..184F . And there are several discussions here on CN about how to come up with a good soot plate, probably most prominent see https://www.cloudyni...93-lyot-tester/ .
What I am wondering about is the following:
1. One basically uses the setup of a Foucault test and applies the soot plate. Ok. But there are "slitted" (two parallel knife-edges) and "slitless" (one KE creating a virtual slit) Foucault testers - and also pinhole setups. The above hyperlinked adsabs-paper says
It also says later that
In combination with the various Foucault test setups of slitted and slitless, I am wondering whether the slitless Foucault setup would not work? Do you really need a real instead of a virtual slit?
Here is an example of a slitted Lyot setup https://www.janvanga...lt/Foucault.htm. On the other hand, in this Lyot setup sketch by Texereau I do not see that the light source is masked besides the soot plate - neither by a real, nor a virtual slit. Do I misread this sketch or is a slit not mandatory? At least in post #37 of the discussion it is said that a slitless tester was tried without results.
2. I am wondering about the pros and cons of using a soot plate that only shows a distinct cut-off on one side of the soot, and a soot plate having a straight line of soot? #42 of the above discussion mentions a link concerning this question, but which doesn't work anymore. Does anyone have some experiences?
3. About the orientation of the soot pattern (single cut-off or soot line). The last image in #45 is quite confusing.
Does the soot have to be orthogonal to the slitted light source?
I rather understand the Lyot test setup to work in such an orientation with the slit and soot being parallel, creating no setup-induced astigmatism at all, just like in the example of the Foucault tester in the link. In the sketch of Texereau above, I would turn the soot line 90°.
Thank you very much for your insights!