[AZ-Observing] Re: Image Question
- From: "Jack Jones" <spicastar@xxxxxxxxxxxxxxx>
- To: <az-observing@xxxxxxxxxxxxx>
- Date: Fri, 5 Sep 2003 18:11:48 -0700
Time to get that 12" done!
Long time Club member Paul Lind performed the testing of the uncoated
Schwaar mirrors and the results were as follows:
Unsigned 14.5" mirror, R=148.5"
Three Foucault tests were done for four zones. Each test was analyzed by
computer curve fitting. Average calculated surface error is 0.068, or
1/15 wave.
An Offner null test was performed and this indicated a very good null
with very faint zone about 1" from the edge. This is not serious and
could not be seen in the Foucault test. The null test could easily
detect a zone even on a 1/15 wave mirror.
Signed 14.5" mirror, R=140.6"
Four Foucault tests were done for four zones. Each test was analyzed by
computer curve fitting. Average calculated surface error is 0.110, or
about 1/9 or 1/10 wave.
An Offner null test was performed and this indicated a very good null.
I was there when Pierre ground and tested my 14.5" mirror also. Test methods
of yore were good enough to detect figure and smoothness on excellent
mirrors and even too good. You got to the limits of your time, patience,
interest, or skill and then pronounced it done. Apparently among mass
producers the point you shot the mirror maker and shipped it varied greatly
with schedule, quality acceptable, and backlog. Zambuto etc. are the
absolute cream and have reputations to uphold, however long it takes, and
even stop taking orders if need be.
Jack Jones
Saguaro Astronomy Club
Public Events
Phoenix AZ
spicastar@xxxxxxxxxxxxxxx
> How do you know that the mirror Pierre ground and polished checked
out
> to 1/15th wave? Was that P-V or RMS. I know how Pierre ground and figured
his
> mirrors I was there when he did my 14 inch mirror. BTW I know how to use a
> knife edge too. I have a 12 inch mirror sitting in my cabinet that I did
under
> Pierre's supervision that just needs final polish and then testing.
>
> As far as Cave mirrors are concerned, They were hit or miss, the
quality
> of the mirror was dependent on how may back orders they had. If they had
to
> ship whether the mirror was ready or not it went off to the coaters the
idea
> being that the new telescope owner would not know the difference!
>
> The mirrors that are coming from Swayze. Zambutto Tom Hall and many
> others are really much better than anything you could get from years
past. There
> are testing methods available today that are much better than what was
> available 30 years ago.
>
> Clear Skies
> Dwight L Bogan
--
See message header for info on list archives or unsubscribing, and please
send personal replies to the author, not the list.
Other related posts:
