ATM Airy disk frustrations

[lifedata@voy.net]

There is a question at the end of this. <g>

The term "airy disk" appeared here a little while back.  I ask a
couple questions about it by email, and didn't grasp it.  I
downloaded several astronomy glossaries.  One said it was something
discovered by an Italian.  another said it was a diffraction pattern
from a star.  The ATM FAQ glossary didn't have it at all.

Yesterday I got my new copy of Texereau.  I gleefully looked in the
index.  Nothing.  I went for the glossary.  NO GLOSSARY!

I started reading.  "Airy disk" didn't appear immediately, but it
said Airy described "defraction disk."

OK, diffraction disk.

Texereau's discussion starts with the diffraction disk and works back
from that to a formula.  But I still haven't figured out exactly what
causes the airy disk/difraction disk.

In testing, a pinhole is used and obviously causes diffraction at the
edges of the material around the pin hole.  What causes diffraction
of a "point source" star?  Is it the intervening media (space dust?
Earth's atmosphere?), or is it something at the scope itself?

Jim L
Posted by MR/2ICE v 1.52 (registered)