Build your own Astronomical Telescopes

This on-line version does not include some of the material supplied on the C/D disk.
Program updates.

             The Reflecting Telescope   alt_11.htm

Mirror Design Overview How Big a Mirror?  

Focal Length and F Number  

Time and Materials

                    Mirror Making   alt_12.htm


The Mirror Workshop  

Rough Grinding

Rough Grinding Large Mirrors  

Fine Grinding  


Pressing the Lap  

Correcting, Mirror Testing  

A Quick Test after the Mirror is Coated

                    Mirror Testing in Detail    alt_13.htm

   Some Basic Optics

             Spherical Aberration

             Testing Amateur Telescope Mirrors

             Distance Between the Radii of Curvature 
                      of a Paraboloid being tested at its Radius of Curvature

             Perceptual Aid in Understanding the Knife Edge Test

             Ronchi Test at the Radius of Curvature

             The Ronchi Program

             The Foucault Program

             How Well Must a Mirror Be Corrected?

             More Mirror Testing Methods

             Reading the Curve of the Mirror with an Eyepiece   

             Using Mirror Edge Diffraction while Mirror Testing


             For Those Who Want More Information About Mirror Testing

             The Caustic Test

             The DAFT Test

             The Null Lens

             The Surf Program

             Strehl Ratio

             Professional Mirror Testing

             Foot Note


Mirror Polishing    alt_14.htm

   Figuring a 'Perfect' Mirror

   Diagnosis of our Mirror's Problems

   Choosing Mirror Testing Methods

   Logging the Mirrors Figure

   The Reference Sphere or Parabola

   Mirror Polisher's Log

   The Mirror Log

   Polish 1 and 2

   Polish 3 and 4

   Polish 5 and 6

   Polish 7 through 14

   Polish 15, Thumbing

   Polish 16, Full Size Lap on Top

   Polish 17, Cool Mirror, Hot Day

   The Sweat Band and Mirror Polishing Temperature

   Polish 18 and 19, The "I" Stroke or Oblating Stroke

   Polish 20, 21 and 22, The Weegee Lap

   Polish 23, The Smoothing "W" Stroke

   Polish 24 and 25, The Weegee Lap and the Mini Weegee

   Polish 26, The Parabolizing Stroke

   Polish 27 Log, A Combination Stroke

   Summary of Figuring

   Masking the Mirror Edge



   Reducing Over Correction

   Smoothing Without Doing Much Else

   Reducing a Turned Edge

   Reducing Zones

   Reducing Dog Biscuit and Ripples

   Combination Strokes

   Inventing New Methods

Mirror Coating Care    alt_15.htm

   Mirror cleaning 

   Beyond mirror cleaning

   De-coating in preparation for recoating 



                    Building the Telescope   alt_21.htm

   Overall picture                  1A

   Base and Tube together   2A

   Tube breakdown               2B

   Base breakdown               2C

   Diagonal size                     3A

   Spider and diagonal          3B

   Building and Installing an Eyepiece and Camera

   Mirror cell design             4A

   Dobson Mirror Cell          4B

   Helpful Suggestions

   Collimation - Aligning the Telescope

   Step by Step

   Finding and the Finder

                Basic Astronomical Optics and Wave Theory   alt_31.htm


   Conic Sections

   Waves or Rays

   Optics Design Using Rays

   Optics Design Using Waves

   On Axis Aberrations

Spherical Aberration

Chromatic Aberration


   Off Axis Aberrations




Our Eyes

Film or Photographic Plate

The Charge Coupled Device (CCD)

   The Cassegrain Telescope

   The Schmidt Camera and the Maksutov Cassegrain

   The Spectrograph and the Diffraction Grating

   Seeing through the Atmosphere

          The Video Camera

          Adaptive Optics

The Sine Wave, Logarithmic and Electronic Calculations   alt_41.htm

            A Quick Review

  Observing Ocean Waves

  Tying Mechanical Waves to Electrical Waves

  An Electrical Power Plant

  Simulation of a Transmission Line Using Finite Elements

  Impedance, the Effect of Resistance and Reactance

  The Quarter Wave Match



  The Mathematical Coincidence of the Chromatic Scale

  Communication Bandwidth

  Signal to Noise Ratio

  Specifying a Wave

The Ary Disk and Diffraction   alt_51.htm

  The Diffraction Pattern 

  The Daytime Terrestrial Telescope

  The Light Bucket 

  The Space Telescope 

  Encircled Energy 

  The Point Spread Function 

  The Modulation Transfer Function 

  Good Seeing 

  More About Testing At The Eyepiece


  Tube Currents

  Spider Diffraction 

  Pinched Optics

  Spherical Aberration 

  Turned Down Edge

  Zonal Aberrations 

  Rough Surface

Links on the Internet



Aluminum Coating

Printed after April 19, 2010.



There is no warrantee of any kind on this program. This program is sold 'as is'. The user must determine the accuracy, appropriateness and safety of all procedures described. Persons purchasing this disk may receive a replacement CD disk if the original disk is found to be damaged.


Recent program updates

December, 2015
We decided to upload most of the C/D disk to the website.
We are also updating links in the process.
The Java applets; Ronchi Program, Surf Program and Sine Wave
will no longer run on Windows so have not been uploaded to the
website. To run these applets will require that they be rewritten.
In the mean time I can yet run them on an old Windows 98 computer.

Program disks may have some links pointing to our old website.  
The new site at Yahoo is:    ( October, 2007 )

The Build your own Telescope Program is improved from time to time.
There is no log of program changes for the entire program other than the date of the file which can be viewed with Windows Explorer. 

May, 2010
We are doing a major job of reformatting for compatibility with wider, high resolution displays.
This project also includes re-proof reading most of the website.  

May, 2010
The Surf Program and the Ronchi Program should be used with the Firefox Browser.
Recent tests with Windows7 / Windows Explorer did not work.
Windows7 / Firefox seems to work fine.

The Surf Program and the Ronchi Program have a log file for past program changes included with program instructions.

If you are using a program disk dated before January, 2006 it is recommended that you email me your address and I will mail a revised disk.  This primarily due to math errors in the Ronchi/Foucault and the Surf  Java Applets.

We intend to fix all known errors with the programs and replace disks for people that have older versions to the extent possible.  If you find a program error email me at

Ronchi Program, recent update log entries.

List of the Ronchi Java Applet modifications, updates or trouble reports.

Most recent at the top.
Dates in yymmdd format.

10-05-19 Updated the instructions at the top of the page instruct.htm.
                  Reformatted HTML pages for wide screen browser displays.

07-01-21 Updated the instructions at the top of the page instruct.htm.

05-07-25 Added functionality to the formula parser such that   TAN   in a formula evaluates the following number to tan(number).
Added functionality to the formula parser such that   IVT   in a formula evaluates the following number to arc tan(number).  ( inverse tangent )

05-07-24 Added functionality to the formula parser such that   S   in a formula evaluates to:  ( r * r ) / 2R


Surf Program, recent update log entries.

List of the Surface Java Applet modifications, updates or trouble reports.

Most recent at the top.
Dates in yymmdd format.

11-02-24 Problem pre-condition: User selects 'View Arrays' on the 'Plot Board' display. (See plot_board.htm, on the disk )
                User then activates 'back' on the browser or 'Back' on the page ( outside of the Java Applet ).
                User then activates 'forward' on the browser.
                The Java Applet will then re-initialize which is normal.
                Problem: A page selection variable is not re-initialized properly causing the Surf Applet to be stuck in the
                 'Display Arrays' page.

                Problem work around: Cause the compiled Java code to be lost by closing the browser.
                This will force the browser to recompile the code from the beginning when the Surf Applet is again selected.

10-05-19 Updated the instructions at the top of the page instruct.htm.
                  Reformatted HTML pages for wide screen browser displays.
                  Re proof read and updated all instructions.

07-01-21 Problem: In the 'First Example' on the file instruct.htm the reiteration of users sample data in step 4 and 5 was incorrect. Corrected

06-01-24 Corrected a small logic error that deactivated 'Zero Arrays' with the wedge display active but in the starward display mode.

05-11-04 Added the 'conic' display which is done when 'Set Pin[o]' is pressed.
Display is at the lower right of the plotting area of the plot board.