[ATM] Star test with laser light sources

["Ray@J-Engineering.com" <Ray@J-Engineering.com>]

Hi All,

I used a 6 mm polished ball bearing and shined a green laser pointer on 
it such that the reflection was directed toward a telescope 350 feet 
away. At this distance the reflection appeared perhaps 10,000 times 
bigger than it should when viewed by eye. Then looking at it with the 
scope, it was a mess. Hundreds of concentric circles and all kinds of 
speckles apparently common to laser pointers?

I’m considering trying a non-lasing red laser diode (with the little 
window removed) as the pinhole. Will I see the same thing?

I went through the same thing when using a laser pointer to test the 
degree of polish in a mirror. I learned that you can’t polish out the 
speckles, duh!

Does anyone have first-hand knowledge of successfully using a laser 
pointer or laser diode in a star test? I am assuming it is critical to 
be able to obtain an in-focus airy disk with several diffraction rings 
around it. I have found that out-of-focus rings are easy to obtain under 
a variety of methods, but in-focus images are much harder, especially if 
you require the airy disk to look stellar. Sound right?

8” f/6.3, no coating.

Ray J



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