I am familiar enough with an actual star test and understands its importance, but is there a test that can be accomplished indoors without an optical bench? Can you simulate a star with a pinhole or LED? Would you still see diffraction rings? I read with interest Rolands test of using tinfoil to reflect sunlight rays and look for color (error)correction...anything along that line for optical abberations with cloudy skies and no stars? Thanks...
Indoor "star" test?
Started by T.R., 10/15/2006 06:07PM
Posted 10/15/2006 06:07PM
Opening Post
Posted 10/15/2006 07:05PM
#1
Yes. A Denver area astro dealer does this to check--and adjust, if required--collimation on telescopes. The scope under test is set up on a bench, and the light source (precision laser drilled peep hole that is a few microns diameter, as I recall) used as an artificial star.
Ron
Equipment Forum co-moderator
Ron
Equipment Forum co-moderator
Posted 10/15/2006 07:36PM
| Edited 10/15/2006 08:58PM
#2
I am familiar enough with an actual star test and understands its importance, but is there a test that can be accomplished indoors without an optical bench? Can you simulate a star with a pinhole or LED? Would you still see diffraction rings?
Yes, you can do indoor star test. For light source I
use a 1mm ball bearing illuminated by a small high
intensity lamp about 4 feet away from the ball bearing.
Telescope is about 40 feet away. This works OK for
scopes up to about 4" or 5" aperture.
Yes, there are diffraction rings. It is good test
for alignment issues -- coma and astigmatism can be
accurately judged. But spherical error is introduced
by having the "star" too close, so those errors
cannot be accurately determined. You also might
need an extension tube to reach focus.
If the scope is very tightly baffled, there might be
some vignetting due to focus change. But usually
this is not an issue.
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