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"Star Testing Astronomical Telescopes: A Manual for Optical Evaluation and Adjustment"
Second Edition by Harold Richard Suiter

Hardcover - 413 pages, Second Edition April 2009
Willmann-Bell, Inc. publishers; ISBN: 09780943396903
Dimensions (in inches): 9-¼ x 6-¼ x 1-1/32
Other Available Editions: None

Left: Cover of the book (12,941 bytes).
Click on image to view enlargement (53,916 bytes)

"Star Testing Astronomical Telescopes" is among those few up to date books which Company Seven recommends to those persons who have decided to buy an astronomical telescope or for those who are now considering the choice of astronomical telescope. This is a book which can be most helpful when you receive a new telescope. It will teach you how to determine if your new telescope has an optical gross anomaly that should justify its return for an exchange. If you bought your telescope at Company Seven then you probably do not need "Star Testing Astronomical Telescopes" since we routinely perform quality control inspections of every newly arrived telescope. But since most telescopes are roughly handled during shipping even those sensitive systems sent from Company Seven may arrive out of proper alignment. "Star Testing Astronomical Telescopes" teaches one how identify if a telescope is out of adjustment ("collimation"), and it will provide insights into how to remedy it.

This book is a remarkable accomplishment. Previously there were no books that were affordable by most amateurs, and which could be understood by anyone less than a College mathematics expert on this subject. Not that all of the content in this book will be understood by everybody, but the concepts and what one should look to see in a telescope are readily understood by the typical enthusiast. Anyone from about High School age and older should find the book readable, interesting, and informative. "Star Testing Astronomical Telescopes" is concise, and well illustrated. However, this is not light or casual reading; one needs to read it carefully, and maybe a few times in order to grasp the large quantity of information provided.

This remains one of a very few titles that discusses those optical systems that an amateur or small college are likely to encounter. And it's topics that are likely to remain relevant, even if the technology of lens designs changes somewhat over the forseeable future.

The Second Edition adds and expands on many areas, yet deletes the previous edition discussion of the Hubble Space Telescope spherical aberration.

Caveat Emptor! This title has produced some unjustified customer concern and returns since it is possible for the casual reader to misunderstand some of the information. So please understand:

  • A little knowledge can be a dangerous thing, this book requires careful reading.

  • Understand the optics provided in the better amateur telescopes are usually relatively good however, there can be some inconsequential or notable variances of quality and price even more so in mass production telescopes.

  • Not everybody needs to buy or can afford to buy a "Ferrari" telescope (Astro-Physics, Carl Zeiss, Questar, TeleVueTeleVue, etc.). And a "Ford" or "Chevrolet" telescope Celestron or Meade Instruments for example) does not have to meet the theoretical limits of perfection in order to provide the owner with years of excellent service.

"Star Testing Astronomical Telescopes" is The Bible of telescope Star Testing testing and adjustment. It is a great choice for those who wish to better understand their telescopes, and possibly improve the performance of that telescope. When this book was introduced in 1994 it soon became "the book many telescope manufacturers do not want you to read" because it so readily could demonstrate the shortcomings and inconsistencies of many of the mass produced, amateur grade telescopes.

Martin Cohen, Company Seven

The Star Test Rather than narrowing the scope of the book to testing individual components, Suiter's focus of the book is a test method that can be used at the observing site, so that all the problems that impact on a telescope's performance can be diagnosed. The star test is such a method. It uses the entire working aperture and all the elements of a telescope. It is not a poor substitute or a work-around that uses bits and pieces of the optical system. It is the oldest and most sensitive of the optical tests—an inspection of the diffraction image itself. The Star-Test is not new technology, it is an appropriate and discerning technique. The concepts of the Star-Test were used as far back as 1722 when John Hadley used it when making the earliest astronomical Newtonian reflecting telescopes.

Star-test results apply to the complete imaging performance of the telescope. The star test is lightning-fast and requires only a good high-power eyepiece. It tests the telescope for precisely what it was meant to do. Bad or poorly-aligned instruments fail the star test unambiguously. The star test often allows you to correct the optical difficulty immediately in the field, when you might be frantic to have your telescope perform well to observe a once in a lifetime event.

StarTest1.jpg (37161 bytes)

Above: Examples of Star-Test diffraction pattern images from the book (37,161 bytes)

While the star test has been around for centuries learning it has often been hampered by messy mathematics and its visual nature. Most people who use it have learned it at the elbow of a patient Master. In this book, Suiter becomes your Master. He carefully shields you from difficult diffraction theory and uses advanced computer generated graphics to show you the appearance of each aberration. Again and again, you will look at these graphics and say “I've seen that before. So that's what it was!” The star test is a powerful but inexpensive way of obtaining better resolution and contrast. With this book most observers will find that they don't need a new telescope because they now can test, diagnose and fix the one they have. Using "Star Testing Astronomical Telescopes" as a guide, your telescope will perform to the best of it's abilities and perhaps it will show images better than you would have believed possible.

In Chapter 2 the author has a "condensed" Star-Test Manual for those who want a quick start into testing. The following chapters go into more detail about fine points, and theory. For those who can not get a telescope out on enough good quality nights to Star Test, Suiter describes how to employ an artificial star that can be used at one's convenience.

Table of Contents

    indicates new or notably revised in Second Edition

An Introduction to the Author

1. Introduction
    1.1. Telescope Evaluation
    1.2. Testing the Surfaces
        1.2.1. Sources of Errors
        1.2.2. Measures of Optical Quality
        1.2.3. The Modulation Transfer Function
    1.3. The Star Test—A Brief Overview
        1.3.1. Diffraction Rings
    1.4. The Reason for Star Testing
2. An Abbreviated Star-Test Manual
    2.1. Some Necessary Preliminaries
    2.2. Optical Problems in Turn
        2.2.1. Secondary Mirror Obstruction
        2.2.2. Misalignment
        2.2.3. Atmospheric Motion and Turbulence
        2.2.4. Tube Currents
        2.2.5. Pinched or Deformed Optics
        2.2.6. Spherical Aberration
        2.2.7. Rough Surfaces
        2.2.8. Zonal Aberrations
        2.2.9. Turned Edges
        2.2.10. Astigmatism
    2.3. Concluding Remarks
3. Telescopes Are Filters
    3.1. Perceptions of Reality
    3.2. A Comparison to Audio
        3.2.1. Aperture Diameter/Size of Speakers
        3.2.2. Colored Filters/Equalizer Filters
        3.2.3. Image Processing/Signal Processing
        3.2.4. 3.2.4 Scattered Light/Audio Noise
        3.2.5. Spatial Frequency/Audio Frequency Responses
    3.3. The Modulation Transfer Function (MTF)
    3.4. The MTF in Use
        3.4.1. MTF Associated with Defocusing
        3.4.2. Stacking of MTFs
        3.4.3. MTF In Every Direction
        3.4.4. The Black Box
        3.4.5. Shape of the MTF Curve Related to Form of the Image
        3.4.6. Measuring the MTF
4. Diffraction
    4.1. The Coordinates of Light
    4.2. The Consequence of Filtering
    4.3. The Huygens Model
        4.3.1. Diffraction and Focusing
        4.3.2. Fresnel Zones
        4.3.3. Fresnel Zones with Defocus
    4.4. Nodes and Antinodes
    4.5. Other Aberrations—The Pupil Function
5. Conducting the Star Test
    5.1. Defocusing and Sensitivity
        5.1.1. Focuser Motion Related to Defocusing Aberration
        5.1.2. Sensitivity of the Star Test
    5.2. Artificial Sources
        5.2.1. Distance of Artificial Sources
        5.2.2. Diameter of Artificial Sources
        5.2.3. Using a Reflective Sphere Instead of a Pinhole
        5.2.4. Setting Up a Nighttime Artificial Source
    5.3. Performing the Test
        5.3.1. 8-Inch f/6 Newtonian Reflector
        5.3.2. 16-Inch f/4 Dobson-mounted Newtonian
        5.3.3. 6-Inch f/12 Apochromatic Refractor
        5.3.4. 8-Inch f/10 Schmidt-Cassegrain Catadioptric
        5.3.4. 6-Inch f/12 Maksutov-Cassegrain Catadioptric
6. Misalignment
    6.1. Kinematic View of Alignment
    6.2. Effects of Misalignment
    6.3. The Aberration Function of the Misaligned Newtonian
    6.4. Filtration of a Misaligned Newtonian
    6.5. Aligning Three Telescopes
        6.5.1. The Newtonian Reflector
        6.5.2. The Refractor
        6.5.3. The Schmidt-Cassegrain
7. Air Turbulence and Tube Currents
    7.1. Air As a Refractive Medium
    7.2. Turbulence
        7.2.1. The Aberration Function
        7.2.2. Filtering Caused by Turbulence
        7.2.3. Observing Turbulence
        7.2.4. Corrective Action
    7.3. Tube Currents
        7.3.1. The Aberration Function
        7.3.2. Filtering of Tube Currents
        7.3.3. Observing Tube Currents
        7.3.4. Corrective Actions for Tube Currents
8. Pinched and Deformed Optics
    8.1. Causes
    8.2. The Aberration Function
    8.3. Filtering of Pinched Optics
    8.4. Diffraction Patterns of Pinched Optics
    8.5. Fixing the Problem
9. Obstruction and Shading
    9.1. Central Obstruction
        9.1.1 The Systems Viewpoint of Central Obstruction
        9.1.2 Unobstructed Systems
    9.2. Spider Diffraction
    9.3. Shading or Apodization
    9.4. Dust and Scratches on the Optics
    9.5. Conclusions
10. Spherical Aberration
    10.1. What Is Spherical Aberration?
    10.2. Generalized Spherical Aberration
    10.3. The Aberration Functions
    10.4. Correction Error (Lower-Order Spherical Aberration)
        10.4.1. Filtering of Spherical Aberration
        10.4.2. Monochromatic Star-Test Patterns of Correction Error
        10.4.3. Polychromatic Star-Test Patterns of Correction Error
    10.5. A Compact, Uniform Standard for Optical Quality
        10.5.1. Tolerable Errors
    10.6. Estimation of Low-Order Spherical Aberration
        10.6.1. Estimates of Large Amounts of Low-Order Spherical Aberration
        10.6.2 Method For Estimating Small Correction Errors
                 (Based on Technique of Ellison)
    10.7. Conclusion
11. Circular Zones and Turned Edges
    11.1. Higher-Order Spherical Aberration
        11.1.1. Star-Test Pattern of Consumer Maksutov-Cassegrains
        11.1.2. Premium Commercial Maksutov-Cassegrains
        11.1.3. Filtering Pattern of the Three Maksutovs
        11.1.4. Encircling Engery Ratio of High-Order Spherical Aberration
        11.1.5. Judging the Amount of Higher-Order Error
    11.2. Causes of Other Zonal Defects
    11.3. Interior Zones
        11.2.1. Aberration Function of S-Zones
        11.2.2. Filtering of S-Zones
        11.2.3. Detecting Interior Zones in the Star Test
    11.3. Turned Edges
        11.3.1. Aberration Function
        11.3.2. MTF of Turned Edge
        11.3.3. Image Pattern of Turned-Down Edge
        11.3.4. Signal-to-Noise Ratio of a Turned Edge
        11.3.5. The Width of the Turned Edge
        11.3.6. Remedies for Turned Edge
12. Chromatic Aberration
    12.1. Dispersion
    12.2. The Achromatic Lens
    12.3. Residual Chromatic Aberration
    12.4. The Apochromat
    12.5. Testing Refractors for Geometrical Aberrations
    12.6. The Star-Test for Chromatic Effects
        12.6.1. Wedge, Assembly Errors, and Atmospheric Spectra
        12.6.2. Star Test for Conventional Astronomical Visual Doublets
        12.6.3. Star-Test of Apochromats or Advanced Refractors
        12.6.4. Chromatic Effects in the Eye
        12.6.5. The Eyepiece   
    12.7. The MTF's of Corrected Refractors
    12.8. Conclusions and Remedies
13. Roughness
    13.1. Roughness Scales and Effects
    13.2. The Terminology of Roughness
    13.3. Medium-Scale Roughness, or Primary Ripple
        13.3.1. The Aberration Function of Medium-Scale Roughness
        13.3.2. Filtering Effects of Medium-Scale Roughness
        13.3.3. Star-Test on Medium-Scale Roughness
        13.3.4. Roughness and Turbulence
    13.4. Small-Scale Roughness, or Microripple
        13.4.1. The Aberration Function of Small-Scale Roughness
        13.4.2. Filtering of Small-Scale Roughness
        13.4.3. The Great Unknown
14. Astigmatism
    14.1. Astigmatism in Eyes and Telescope Optics
    14.2. Causes of Astigmatism
    14.3. Aberration Function of Astigmatism
    14.4. Filtering of Astigmatism
    14.5. Star-Test Patterns
    14.6. Identification in Newtonian Reflectors
    14.7. Refractors or Schmidt-Cassegrains
    14.8. Spherical Deformation of Diagonal Mirrors
    14.9. Remedies
15. Accumulated Optical Problems
    15.1. Breaking the Camel's Back
    15.2. Fixing the Telescope
    15.3. Errors on the Glass
    15.4. The Myth of the Complex Telescope
    15.5. Testing Other Telescopes
    15.6. When Everything Goes Right
A. Other Tests
    A.1. The Foucault Test
    A.2. The Hartmann Test
    A.3. Resolution of Double Stars
    A.4. Geometric Ronchi Test
    A.5. Interferometry
       A.5.1. How Do Interferometers Work?
       A.5.2 Interferometers
    A.6. The Null Test
    A.7. The Roddier Test
B. Calculation Methods
    B.1. Diffraction Concepts
    B.2. The Fraunhofer and Fresnel Approximations
    B.3. Image Calculations for Symmetric Apertures
    B.4. Image Calculations in ASYMM for Nonsymmetric Apertures
    B.5. Use of Programs
        B.5.1. Symmetric Pupil Function
        B5.2. Asymmetric Pupil Function
    B.6. Verification of Numerical Procedure
        B.6.1. Comparison of the Three Programs
        B.6.2. A Numerical Comparison with an Analytic Solution
        B.6.3. Comparison with Published Patterns
        B.6.4. Calibration of ZEMAX Grayscale Polychromatic Images
    B.7. Numerical Limitations on Programs
    B.8. A Note on Apodization
    B.9. Difficulties in Printing
    B.10. Viewing ZEMAX Rendering
C. Diagonal Calculations
    C.1. Derivation of Minor Axis and Offset
        C.3.1. Test Case
    C.2. Minor Axis and Offset Approximations
    C.3. Tolerance for Spherical Deformation in the Diagonal
D. Labeling of Diffraction Patterns
E. Eyepiece Travel and Defocusing Aberration
F. Glitter in a Shiny Sphere
G. Specific Designs Used in the Main Text
H. List of Common Symbols

Introductory Price $34.95 (U.S.D.); please add $8.00 for domestic postage, or $12.00 for international postage.

The Author:

Suiter200281.jpg with Astro-Physics telescope (11,605 bytes)

Harold Richard Suiter is an experimental physicist who has worked on such diverse topics as the energy levels in atoms, multi-particle decay reactions in nuclei, and scattering of sound from underwater structures.

Richard Suiter with one of our with Astro-Physics 6" (155mm) Apo telescope on home made Alt-Az mount and tripod (11,605 bytes).

He became an avid binocular astronomer at age 11 since he was fortunate enough to see the Milky Way from his parents backyard in Hillsboro, Ohio. During his formative years, he acquired a taste for galactic clusters, dark nebulae, and loose stellar associations. He has been an amateur telescope maker since 1978, having completed a diverse array of instruments. And owning a broad range of other telescopes including an Astro-Physics Apo - one of very few new telescopes to provide a "textbook" perfect Star-Test pattern. He has been affiliated with astronomy clubs including the Columbus Astronomical Society. Suiter currently observes from the tranquil yet hazy skies near Panama City, in northwest Florida. He holds a Ph.D. degree in physics from Ohio State University.


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