Re: ATM Foucault testing : confusion

[Achim Schaller <acschaller@geocities.com>]

BOB PRABOWO schrieb:

> My question: is center of curvature = radius of curvature?

Hi Bob,

radius of curvature means the distance between center of curvature and
mirror (curve)

> focal length is 71cm, so I placed the tester 142 cm from the mirror.

That is the right place

> 2. Does the focus image (the smallest spot of light reflected by the
> mirror) fall on the knife edge (the focal point falls on the knife edge)?
> Or should it fall on the scope's lens?

As you said above, you placed it at the center of curvature, not at the
focal point. So there is no focused image. In fact, what you should see is
the whole mirror being lighted up. Nevertheless the image you want to see
should fall into the lens.

> 3. Should the micrometer knob reads 0.0 at the focal point?

No, you are only interested in the differences between the readings

> 5. Does the room where I do foucault testing have to be completely dark?

I find it easier when its not totally dark, because then you can see the
mirror when trying to find the reflection of the lightsource.

Clear skies,   ...Achim

--
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Achim Schaller
acschaller@geocities.com
http://www.geocities.com/yosemite/6999/
(Astrophotography & Photography)
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