Re: Kilian's Mirror: E&W results look good.

Jan R. Sugalski (afn19866@freenet.ufl.edu)
Mon, 24 Apr 1995 23:35:27 -0400 (EDT)

Mr. Kilian: Regarding the double pass method of testing mirrors, this doubles the actual error of the optical surface. Therefore if the test was giving 1/4 wave the actual error would be 1/8wave. When refractor objectives are tested by auto-collimation, for instance, the light passes thru the lens twice and thereby doubles the error. What this means is that if the lens looks good under a double pass of the light, it is REALLY good. Achro

On Tue, 25 Apr 1995, Alan Kilian wrote:

> Date: Tue, 25 Apr 1995 01:34:46 GMT
> From: Alan Kilian <kilian@ironwood-fddi.cray.com>
> To: atm@best.com
> Subject: Kilian's Mirror: E&W results look good.
>
>
> I talked to the guy at E&W today, and his report, although a bit terse,
> seems to say I have a good mirror.
>
> He said that the extreme edge is turned down (Big surprise there), and
> that the outer 1/4 Inch might get "Fuzzy" when aluminized since it's
> not polished completely.
>
> He said it has a "good" parabola. He wouldn't wave rate it though.
>
> I did tie him down, and he said "good" is a maximum of 1/4 Wave
> wavefront error, so a maximum of 1/8 Wave surface error since they use a
> two-pass system. (Whatever that is)
>
> So, I'm ordering a small diagonal (1.5 Inches minor axis) for visual
> work, and I hope to put the uncoated mirror in Dale Eason's tube
> so that I can star test it before aluminizing.
>
> Someday, I'll re-polish to get the edge polished, but I need to get
> the tube and mount built, and thenlook at some stars first.
>
> In the mean time, I'll mask it to a 7.5 Inch f/7.6 F 56.9 Inch mirror.
>
> -Alan Kilian
>