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Hi Werner
There are two ways commonly used to set up the ronchi test:
1) use a very compact light source and shine it through one end of the ronchi screen while you observe the reflected image from the mirror through the other.
I think a krypton bulb will be too big. The stellafane video on autocollimation is dated 2009. These days most people get a bright small white LED.
2) The other way is how it was always done on the past and may suit you if your grating is small. Create a small slit - eg with two razor blades. I prefer to use the blades from pencil sharpeners. They are small, only sharp on one side and have a hole for a screw.place the LED behind the slit. If your mirror is of moderate focal length, a bit of separation between the slit and grating won’t hurt. You need to have the grating angled the same way as the grating - ie as vertical as possible. In the other method, this happens automatically.
I usually place a torch in front of the slit to help me roughly line things up.
Rod.
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