19 Sep
2011
19 Sep
'11
8:26 a.m.
On 9/18/11, jcarman6@q.com <jcarman6@q.com> wrote:
Refractors do not have central obstructions. They take ALL the light from a source and focus it at a single point.
Ok, it occured to me that you were referring to the Airy disk. But refractors do not focus all the light to a point. They tend to bring more energy into the central spot but they do have interference fringes around the spot. There is no perfect optical system.