Monday, July 27, 2009

Star Image Out of Focus for Collimation

Here's an excellent video of an out of focus star image being used to collimate a telescope.

The diffraction rings and the little dot in the center (not the star!) are all optical effects. This is all light from a single star but everything you see is caused by the telescope optics or atmosphere.

The dark hole in the center is caused by the secondary mirror obstruction. The whole image is the light filling the aperture of the telescope.

The shimmering and bouncing of light is all atmospheric seeing effects.

The fact that the central hole and the rings are all concentric show that the telescope is well-collimated.