To: atm{at}shore.net
From: "Matthew L. Brown" 
Reply-To: "Matthew L. Brown" 


This mirror is heading to my brother, who will build his first telescope
along with his 8 year old.  My brother is an excellent woodworker and
technically competent.  I'm hoping he makes something very interesting.  
They live in Tokyo, so the planets are just about the only
thing that he'll be able to see.  However, they do get to the west coast
pretty often,  where the skies are much nicer.  So, Colin, thanks for the
encouragement.   Meanwhile brother #2 has dug up a little 3" reflector
for
his 5 year old that he wants me to refurbish...

Latest foucault:
http://host67.everstrive.com/~mlbrown/ASTRONOMY/Foucaultgram23Mar.jpg
The edge has improved, and I've made a little hole in the middle.    My
measurements were not nearly as consistent as yesterday (perhaps the small
hole in the middle of the larger central zone confused my eye). Tex
results:
Comments:    Optical diameter: 4.15
   Readings per zone: 4
Radius of curvature: 76.62
                 f/D:  9.23
    Diffraction disc: 0.000243264

  1 ZONE                1          2          3
  2 h(x)              1.1980     1.6940     2.0750
  3 h(m)              0.5990     1.4460     1.8845
  4 hm**2/R           0.0047     0.0273     0.0464
  5 hm/4f             0.0039     0.0094     0.0123
  6 D1                0.0683     0.0628     0.0495
  7 D2                0.0683     0.0628     0.0495
  8 D12               0.0683     0.0628     0.0495
  9 D12 -  0.0177     0.0505     0.0450     0.0318
10 Lamda c           0.0458     0.0177    -0.0146
11 Lamda f * 1e5      17.92      16.74     -17.92
12 Lamda f / rho      0.737      0.688     -0.737
13 u * 1E6            -4.68      -4.37       4.68
14 Wavefront          -3.61      -3.78       0.00
         Reference parabola: y = -1.39098 * x**2 + 0
         passing through (  0.00,  0.00) and (  2.08,  0.00)

Maximum wavefront error = 1 / 5.7 wave at zone 2

Results for individual sets of readings:
         Reading set 1: 1 /  5.2 lamda, Max Trans Abberation=1.01
         Reading set 2: 1 /  5.3 lamda, Max Trans Abberation=0.86
         Reading set 3: 1 /  4.5 lamda, Max Trans Abberation=0.86
         Reading set 4: 1 /  6.0 lamda, Max Trans Abberation=0.67


Sixtests says Strehl about 0.89.


For those who asked, here is a photo of the lap, mirror, etc. (WARNING 1MB JPEG file)
http://host67.everstrive.com/~mlbrown/ASTRONOMY/DSCN1390.JPG

Now I'm off to hit this one for about 1 minute of 1/4 diameter W strokes,
and that should do it.

=Matt


>Delivered-To: mlbrown{at}0
>From: "CSC" 
>To: "Matthew L. Brown" 
>Subject: RE: Re: ATM Getting less edgy
>Date: Sun, 23 Mar 2003 20:03:36 -0500
>X-Mailer: Microsoft Outlook IMO, Build 9.0.2416 (9.0.2910.0)
>Importance: Normal
>
>It's within 1/8 wavefront of a paraboloid.  Practically perfect as a sphere.
>You can get 1/30 wavefront with a screw on the back and flex it.
>
>-good edge, and it'll be a real planet whacker.
>
>I refigured an Edmund 4.25 which was quite overcorrected. I replaced the
>diagonal which was 2 waves from flat, and it works SO well on the planets.
>I am excited about MARS with it.  The small aperture makes it a moon/planet
>killer even when the seeing is not great. Much fun.
>
>Colin

--- BBBS/NT v4.00 MP