Astronomical Photometry, Text and Handbook for the Advanced Amateur and Professional Astronomer

410 Pages·1990·7.73 MB·English

by  Arne A. Henden

ASTRONOMICAL
PHOTOMETRY
A Text and Handbook
for the Advanced Amateur
and Professional Astronomer
Arne A. Henden
Ronald H. Kaitchuck
Department of Astronomy
The Ohio State University
Published by
Willmann-BellJnc. «-—
gO. Box 35025
Richmond, Virginia 23235 © (804)
United States of America 320-7016 *"-
Published by Willmann-Bell, Inc.
P.O. Box 35025, Richmond, Virginia 23235
Copyright ©1982 by Van Nostrand Reinhold Company Inc.
Copyright ©1990 by Arne A. Henden and Ronald H. Kaitchuck
All rights reserved. Except for brief passages quoted in a review, no part of
this book may be reproduced by any mechanical, photographic, or electronic
process, nor may it be stored in any information retrieval system, trans-
mitted, or otherwise copied for public or private use, without the written
permission of the publisher. Requests for permission or further information
should be addressed to Permissions Department, Willmann-Bell, Inc. P.O.
Box 35025, Richmond, Virginia 23235.
First published 1982
Second printing, with corrections 1990
Printed in the United States of America
Library of Congress Cataloging-in-Publication Data
Henden, Arne A.
Astronomical photometry : a text and handbook for the advanced
amateur and professional astronomer / Arne A. Henden, Ronald H.
Kaitchuck
p. cm.
Includes bibliographical references.
ISBN 0-943396-25-5
1. Photometry, Astronomical. I. Kaitchuck, Ronald H. II. Title.
QB135.H44 1990 90-11908
522'.62-dc20 CIP
PREFACE
Most people who do astronomical photometry have had to learn the
hard way. Books for the newcomer to this field are almost totally lack-
ing. We had to learn by word-of-mouth and searching libraries for what
few references we could find.
The situation improved markedly after we began our graduate stud-
ies in astronomy at Indiana University. We then had access to profes-
sional astronomers with many years of experience in photometry. Indi-
ana has a very good astronomical library, and the copy machine was
used heavily by both of us. Nevertheless, information was still gleaned
in a piecemeal fashion. It became obvious to us that, as tedious as our
educational process had been, it must be a frustrating experience for
those with more limited reference resources. We were also aware of the
many "tricks" we had learned which somehow never found their way
into print. With this in mind, we set out to write a reference text both
to spare the beginner some of the hardships and mistakes we encoun-
tered, and to encourage others to share in the satisfaction of doing
meaningful research.
Our basic approach was to create a self-contained book that could be
used by the interested amateur with little or no college background, and
by the astronomy major who is new to photometry. By self-contained,
we mean the inclusion of sections on observational techniques, construc-
tion, and reference material such as standard stars. In addition, we
added substantial theoretical background material. The more esoteric
material was placed in appendices at the back of the book, thereby
retaining the beginning level throughout the bulk of the manual yet pro-
viding heavier reading for the most advanced student.
Photoelectric photometry is a relatively small field of science, and
therefore does not have the large commercial suppliers of instrumen-
vi PREFACE
tation. We have tried wherever possible to indicate sources of equip-
ment, not to recommend any particular brand but to indicate starting
points for any equipment selection procedure. Any implied endorsement
is unintentional.
Similarly, we advocate certain techniques in both the data acquisition
and reduction. There are as many methods in photoelectric astronomy
as there are observers and we will certainly have made some arguable
statements. We have tried to only present techniques that we have used
and found successful.
This book would not have been possible without the dedicated help
of Professor Martin S. Burkhead, who instructed us in observational
techniques and acquainted us with Indiana University facilities, and
Professor R. Kent Honeycutt, who provided much of our theoretical
background knowledge by course material and stimulating conversa-
tions. Both these professors, Russ Genet and Bob Cornett have proof-
read much of the text for which we are very grateful. We would also
like to thank Thomas L. Mullikin for writing the section on occultation
techniques. Our wives contributed more time and effort into proofread-
ing and correcting than we would like to admit!
We hope that reading this book will instill in you the excitement and
satisfaction that we have found in astronomical photometry. Good luck!
Arne A. Henden
Ronald H. Kaitchuck
CONTENTS
Preface / v
1. AN INTRODUCTION TO ASTRONOMICAL PHOTOMETRY / 1
1.1 An Invitation / 1
1.2 The History of Photometry / 5
1.3 A Typical Photometer / 9
1.4 The Telescope / 11
1.5 Light Detectors / 13
a. Photomultiplier Tubes / 13
b. PIN Photodiodes / 18
1.6 What Happens at the Telescope / 23
1.7 Instrumental Magnitudes and Colors / 25
1.8 Atmospheric Extinction Corrections / 28
1.9 Transforming to a Standard System / 29
1.10 Other Sources on Photoelectric Photometry / 30
2. PHOTOMETRIC SYSTEMS / 33
2.1 Properties of the UBV System / 34
2.2 The UBV Transformation Equations / 37
2.3 The Morgan-Keenan Spectral Classification System / 38
2.4 The M-K System and UBV Photometry / 42
*2.5 Absolute Calibration / 50
2.6 Differential Photometry / 52
2.7 Other Photometric Systems / 54
a. The Infrared Extension of the UBV System / 55
b. The StrOmgren Four-Color System / 55
c. Narrow-Band H/? Photometry / 57
v.i
viii CONTENTS
3. STATISTICS / 60
3.1 Kinds of Errors / 60
3.2 Mean and Median / 61
3.3 Dispersion and Standard Deviation / 64
3.4 Rejection of Data / 66
3.5 Linear Least Squares / 68
*a. Derivation of Linear Least Squares / 69
b. Equations for Linear Least Squares / 70
3.6 Interpolation and Extrapolation / 73
a. Exact Interpolation / 74
b. Smoothed Interpolation / 76
c. Extrapolation / 77
3.7 Signal-to-Noise Ratio / 77
3.8 Sources on Statistics / 78
4. DATA REDUCTION / 80
4.1 A Data-Reduction Overview / 80
4.2 Dead-Time Correction / 81
4.3 Calculation of Instrumental Magnitudes and Colors / 85
4.4 Extinction Corrections / 86
a. Air Mass Calculations / 86
b. First-order Extinction / 88
*c. Second-order Extinction / 90
4.5 Zero-Point Values/ 91
4.6 Standard Magnitudes and Colors / 92
4.7 Transformation Coefficients / 93
4.8 Differential Photometry / 95
*4.9 The (U-B) Problem / 98
5. OBSERVATIONAL CALCULATIONS / 101
5.1 Calculators and Computers / 101
5.2 Atmospheric Refraction and Dispersion / 104
a. Calculating Refraction / 104
b. Effect of Refraction on Air Mass / 106
c. Differential Refraction / 107
5.3 Time / 108
a. Solar Time/ 108
b. Universal Time / 109
c. Sidereal Time / 110
CONTENTS ix
d. Julian Date/ 112
*e. Heliocentric Julian Date / 113
5.4 Precession of Coordinates / 116
5.5 Altitude and Azimuth / 119
*a. Derivation of Equations / 119
b. General Considerations / 122
6. CONSTRUCTING THE PHOTOMETER HEAD / 124
6.1 The Optical Layout / 124
6.2 The Photomultiplier Tube and Its Housing / 128
6.3 Filters/ 134
6.4 Diaphragms / 138
6.5 A Simple Photometer Head Design / 141
6.6 Electronic Construction / 147
6.7 High-Voltage Power Supply / 149
a. Batteries / 149
b. Filtered Supply/ 150
c. RF Oscillator / 153
d. Setup and Operation / 155
6.8 Reference Light Sources / 155
6.9 Specialized Photometer Designs / 157
a. A Professional Single-beam Photometer / 157
b. Chopping Photometers/ 159
c. Dual-beam Photometers / 161
d. Multifilter Photometers / 163
7. PULSE-COUNTING ELECTRONICS / 167
7.1 Pulse Amplifiers and Discriminators / 167
7.2 A Practical Pulse Amplifier and Discriminator / 170
7.3 Pulse Counters / 172
7.4 A General-Purpose Pulse Counter / 173
7.5 A Microprocessor Pulse Counter / 178
7.6 Pulse Generators / 181
7.7 Setup and Operation / 182
8. DC ELECTRONICS / 184
8.1 Operational Amplifiers / 185
8.2 An Op-Amp DC Amplifier / 188
8.3 Chart Recorders and Meters / 193
x CONTENTS
8.4 Voltage-to-Frequency Converters/ 195
8.5 Constant Current Sources / 196
8.6 Calibration and Operation / 197
9. PRACTICAL OBSERVING TECHNIQUES / 202
9.1 Finding Charts / 202
a. Available Positional Atlases / 203
b. Available Photographic Atlases / 204
c. Preparation of Finding Charts / 205
d. Published Finding Charts / 206
9.2 Comparison Stars / 207
a. Selection of Comparison Stars / 208
b. Use of Comparison Stars / 209
9.3 Individual Measurements of a Single Star / 210
a. Pulse-counting Measurements / 210
b. DC Photometry/ 213
c. Differential Photometry/ 216
d. Faint Sources/ 218
9.4 Diaphragm Selection / 220
*a. The Optical System / 220
*b. Stellar Profiles / 223
c. Practical Considerations / 224
d. Background Removal / 226
e. Aperture Calibration / 227
9.5 Extinction Notes / 228
9.6 Light of the Night Sky / 229
9.7 Your First Night at the Telescope / 231
10. APPLICATIONS OF PHOTOELECTRIC PHOTOMETRY / 238
10.1 Photometric Sequences / 238
10.2 Monitoring Flare Stars / 240
10.3 Occultation Photometry / 245
10.4 Intrinsic Variables / 248
a. Short-period Variables / 249
b. Medium-period Variables / 250
c. Long-period Variables / 254
d. The Eggen Paper Series / 254
10.5 Eclipsing Binaries / 256
CONTENTS xi
10.6 Solar System Objects / 270
10.7 Extragalactic Photometry / 272
10.8 Publication of Data / 273
APPENDICES / 279
A. First-Order Extinction Stars / 279
B. Second-Order Extinction Pairs / 286
C. UBV Standard Field Stars / 290
D. Johnson UBV Standard Clusters / 297
D.I Pleiades/298
D.2 Praesepe / 298
D.3 1C 4665 / 302
E. North Polar Sequence Stars / 305
F. Dead-Time Example / 308
G. Extinction Example / 311
G.I Extinction Correction for Differential Photometry / 311
G.2 Extinction Correction for "All-Sky" Photometry / 313
G.3 Second-Order Extinction Coefficients / 320
H. Transformation Coefficients Examples / 322
H.I DC Example / 322
H.2 Pulse-counting Example / 327
I. Useful FORTRAN Subroutines / 335
1.1 Dead-Time Correction for Pulse-Counting Method / 336
1.2 Calculating Julian Date from UT Date / 336
1.3 General Method for Coordinate Precession / 337
1.4 Linear Regression (Least Squares) Method / 338
1.5 Linear Regression (Least Squares) Method Using the UBV
Transformation Equations / 339
1.6 Calculating Sidereal Time / 340
1.7 Calculating Cartesian Coordinates for 1950.0 / 341
J. The Light Radiation from Stars / 342
J.I Intensity, Flux, and Luminosity / 342
J.2 Blackbody Radiators / 349
J.3 Atmospheric Extinction Corrections / 351
J.4 Transforming to the Standard System / 355
K. Advanced Statistics / 358
K.I Statistical Distributions / 358
K.2 Propagation of Errors / 361
K.3 Multivariate Least Squares / 363