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Please help. I am running out of Sonotube, money, patience, etc.

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27 replies to this topic

#26 JimmyTrom

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Posted 11 October 2018 - 07:45 AM

No but I will try and contact Louisville Astronomical Society to see if someones has a set-up to see if it is Par or Spherical



#27 JimmyTrom

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Posted 11 October 2018 - 08:10 PM

EeeeeYouw says MiniMe.  How do I tell the difference?



#28 drneilmb

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Posted 11 October 2018 - 09:14 PM

EeeeeYouw says MiniMe. How do I tell the difference?


One way to tell the difference is to put it in a temporary "telescope" and point it at a bright star. (Polaris is bright and won't swing out of the field of view while you lean a couple sticks against a lawn chair.)

If the mirror is spherical rather than parabaloidal, then the spherical aberration at that fast focal ratio will probably make it impossible to focus a star to a point at high magnification.

In general the process is known as star testing, and it can give extremely detailed information on the precise "figure" of the mirror, but in this case, the crudest version of star testing will suffice to see if the mirror can form a decent image of a star, and at what magnification.


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