AAVSO Photoelectric Photometry (PEP) Manual
Download Version 3.0 Now (1.9 MB)
by Tom Calderwood
[A translation of Version 1.0 of this Guide into French is available below]
Our vision: High quality photometry of bright, astrophysically interesting stars.
The AAVSO photoelectric section was founded in the late 1970s. We use old-school technology, but we can get superior results on bright stars. Compared to CCD or DSLR systems, our equipment is fundamentally simpler to calibrate and operate, and data reduction is straightforward. What we lack in sensitivity, we make up for in quality. With properly chosen targets and careful technique, we remain a viable research group. Talk to us—we're friendly people, and there is no substitute for conversations with experienced observers. Our web page is at: https://www.aavso.org/content/aavso-photoelectric-photometry-pep-program.
This document is a work-in-progress, representing my best understanding of PEP as practiced at AAVSO. It lacks the polish of other AAVSO manuals, but I think you will find it entertaining reading. The content lies somewhere in between a cookbook and a reference book. I will try to provide a wide, but not too deep overview of the equipment and practice of photometry with single-channel photometers. I will fudge on the details, occasionally, in the service of clarity.
Table of Contents
Chapter 1 — Observing
1.1 Scopes and Mounts
1.2 Photometers and Filters
1.3 Basic Operation
1.4 Setting the Gain and Integration Time
1.5 The Standard Sequence
1.6 Skies: the Good, the Bad, and the Ugly
1.7 Tricks of the Trade
1.8 Extra notes on the SSP5
1.9 Our Mascot: Count von Count of Sesame Street
Chapter 2 — Technical Details
2.1 The Magnitude System
2.2 Time and Date
2.3 Star Identifiers
2.4 Photometric Bands
2.5 Response Curves
2.6 Single Channel Photometry
2.7 The Sinkhole
Chapter 3 — Data Reduction
3.1 Software
3.2 Data Management
3.3 Observational Honesty
3.4 Avoiding Embarrassment
3.5 Gory Details of Reduction
3.5.1 Instrumental Magnitudes
3.5.2 First-order Extinction
3.5.3 Color Contrast
3.5.4 Second-order Extinction in B Band
3.5.6 Transformation
3.5.7 Complete Magnitude Reduction Formulae
3.5.8 Airmass Reduction
3.5.9 Time of Observation
3.5.10 Metadata (data about the data)
3.5.11 Reference Magnitudes
3.5.12 AAVSO Extended Data File Format
Chapter 4 — A Quick Digression on Statistics
4.1 Precision
Chapter 5 — Calibration
5.1 First-Order Extinction
5.2 Transformation (the easy way)
5.3 Transformation (the hard way)
5.4 Second-Order Extinction
Appendix A: PEPObs
Appendix B: References
Appendix C: Metadata
Appendix D: Extinction Examples
Appendix E: SSP Electronics
Appendix F: Additional Notes
Appendix G: "Starparm" Target List file
Appendix H: Cutting Corners on Sky Samples
Appendix I: Built-in Counter Overflow
Appendix J: When I reduce data for you
Appendix K: SSP Linearity
Appendix L: War Stories
Appendix M: Constant Stars
Appendix N: Erratic Counts
Appendix O: External Data Logger
English - Version 3.0 (1.9 MB, issued 5 April 2025)
English - Version 2.0 (1.4 MB, issued 28 May 2020)
English - Version 1.0 (4.5 MB, issued 17 January 2017)
Translations
French - Version 1.0 - translated by Bernard Candela (January 2018).