CHOICE Course Descriptions

Return to CHOICE in Astronomy


Most courses are available to AAVSO members AND the general public. The fee for AAVSO members is $35.00 and for non-members $60.00. Registrations are available on a first-come, first-served basis and must be purchased through the AAVSO Store when the "Purchase" link is present in the schedule of courses.

The following are prerequisites and descriptions of each CHOICE course:


Advanced Use of AstroImageJ for Exoplanet Observing

This course is designed to provide current users of AstroImageJ (AIJ) with the opportunity to hone their exoplanet observing skills using AIJ and to discover some “hidden gems” about AIJ. The course will not only cover how to use some of AIJ’s advanced features, but it will also take some of the mystery out of what AIJ does in such areas as model building and detrending. Whether you are currently participating in the TESS Follow-Up Observing Program (TFOP) or desire to, this course should help you improve the quality of your exoplanet observations.

In order to better respond to participants questions and to show in real-time AIJ examples, this course will consist of a series of 1.5 hour live online sessions once a week on Mondays at 7:30pm ET (Tuesdays at 0030 UT) for 6 consecutive weeks. Some sessions will dwell on specific topics selected by the instructor and other sessions will cover topics or techniques that the participants themselves would like to learn more about.

A prerequisite for this course is a working knowledge of AIJ. It is not necessary that participants are part of a formal exoplanet science program, such as TESS, but that they at least should have some experience conducting their own exoplanet observations using AIJ. It is also assumed that participants will have read “A Practical Guide to Exoplanet Observing,’ which can be found at and have installed the latest version of AIJ, including the latest daily updates.


Analyzing Data with VStar

This course is intended for VStar users who have taken and passed the basic CHOICE VStar Course, How to Use VStar. This course assumes that you already know the mechanics of using VStar. The objectives of this course are to provide participants with a better understanding of analysing data with VStar, what you are doing when you use VStar and why it works. That means the course explores basics of underlying theory, limitations of the analysis and valid conclusions one can draw from the results and conclusions that one cannot draw from the results.  The course will also afford ample practice in applying the various analytical tools VStar provides.

This will be achieved by guided reading, exercises (both illustrative and real-world), forum discussions, quizzes, and a final exam or project. The text for the course is Analyzing Light Curves: A Practical Guide, by Grant Foster, which will be applied to the use of VStar. Thanks to the generosity of the author, Grant Foster, the book will be provided in PDF format as part of the course materials for the August 2020 session of the course.

Discussion topics will be created in the course forum for all major course outline sections. Everyone can benefit from questions and comments in such forum topics.

This is not a course on statistics but relevant statistical concepts as they apply to the use of VStar will be introduced through reading and discussion. By necessity this course will use more math than the basic course.



CCD1 and CCD2 have been combined into a single six-week course. We will use the AAVSO Guide to CCD/CMOS Photometry as our basic reference.

This course will use the AAVSO platform VPhot as the basic software for performing tasks such as measuring variables. A brief introduction to VPhot is provided but is not a substitute for taking the CHOICE VPhot course. Students who are not members of AAVSO will be provided temporary access to VPhot for purposes of the course.

This course does not require students to have any equipment, not even a telescope. It does require students to have software for calibrating images and software for graphing data (example, a spreadsheet program). All images used in the first two weeks can be downloaded and processed by the student’s software. All images for the last four weeks will be available to all students as fully calibrated images uploaded to a common VPhot telescope account. When you log onto VPhot those images will appear in your list of images.

Topics covered in the first three weeks are found in Chapters 1-4 of the Guide and include system testing and basic image calibrations from bias and dark frame subtraction to flat fielding. Of interest to experienced astrophotographers are topics such as camera linearity, field-of-view as it relates to differential photometry, signal and noise as they relate to calibration and science images, the nature of photometric filters, and differences between CCD and CMOS cameras.

Topics covered in the last three weeks cover Chapters 5-7 of the Guide include the basics of differential photometry, picking comparison and check stars, ensemble techniques, and measuring variable magnitudes using differential photometry. We will discuss the statistical nature of measurement uncertainty and strategies of accessing the results of measuring a variable. The last two weeks concentrate on using standard star fields to determine transformation coefficients and how to apply those coefficients to transform data into the Standard System for color. We will then finish the course by using variable stars for comparing transformed and non-transformed magnitude estimates and explore ways to evaluate your results.

Success in completing CCD Photometry requires active participation in the Forum discussions and completion of exercises. Participants should plan on devoting sufficient time to the course.

Students are assumed to have suitable software and know how to use it for such activities as taking, manipulating, and analyzing images. If not, please inform the instructor. For photometric analysis the courses actively support the use of AAVSO’s VPhot tool. Before enrolling, please consult the AAVSO Guide to CCD/CMOS Photometry for comments on software. If you are buying photometric filters pay close attention to the spectral characteristics to ensure that they match the Johnson-Cousins color profile.


Developing A Visual Observing Program

This four week course is designed to help visual observers get the most enjoyment and scientific return from the observing programs they develop, based on each individuals’ equipment, observing conditions and interests. To successfully complete this course you must provide in writing, two documents.

1) A complete observer profile (a sample is provided)

2) A list of stars appropriate for your primary observing equipment, observing site and conditions, frequency of observing sessions, scientific merit and fun factor (a sample is provided).


DSLR Photometry

This course will utilize the AAVSO DSLR Observing Manual as its guide. This manual is a basic introduction and guide to using a DSLR camera to make variable star observations. The target audience is first-time beginner to intermediate level DSLR observers, although advanced observers may find the content useful as well.

Important-please read: Camera and software requirements and recommendations


Exoplanet Observing

This course is designed to provide participants with the basics of how to conduct their own exoplanet observations. With the flood of targets coming in from the currently running TESS (Transiting Exoplanet Survey Satellite) mission, this course offering is especially timely.

The first half of the course will cover the fundamentals of high precision photometry, as well as the various phases of an exoplanet observation. The second half will review the use of AstroImageJ (AIJ) for image reduction and exoplanet transit modeling. In addition, the future of exoplanet observing using small telescopes will be discussed, as well as ways in which amateur astronomers can contribute to exoplanet research, including contributions to the TESS mission.

The course will use “A Practical Guide to Exoplanet Observing” as its primary text, as well as a set of sample exoplanet observations, both of which can be found at Videos created by Dennis Conti are associated with each week's module. Participants will take a quiz after each module that assesses your understanding of that week's videos and written materials, and your practice with the transit-fitting software (AIJ). Participants must successfully pass each quiz to successfully pass the course. A private forum will be available to participants in order to communicate with each other, as well as the instructor.


Fundamental Statistics for Photometry

I once asked an astronomer who specialized in “astro-stats” to recommend a good statistics text for self-study. He replied, “There aren’t any.” I suspect this is because textbooks try to cover too much material in too much generality.  Photometry handbooks, by contrast, tend to just serve up statistical formulae without actually explaining where they come from. This course will focus on the mathematical foundations of statistics used by AAVSO observers.

Week One: Gaussian Statistics
Week Two: Uncertainty
Week Three: Poisson Statistics
Week Four: Signal and Noise


How to use VStar

This course is intended to provide participants with a systematic coverage of VStar's current functionality, an appreciation of the ways in which it can be extended, and how it can be used for variable star data visualization and analysis.

You’ll learn how to create mean plots, phase plots, and perform simple period analysis. This is not a course on statistics but relevant statistical concepts as they apply to the use of VStar will be introduced through reading and discussion.

You must successfully complete exercises and weekly quizzes as well as a final examination to pass the course.

VStar is written in the Java programming language, requiring at least version 1.6 to run on Windows, Mac OS X, Linux, and OpenSolaris.


Introduction to Spectroscopy

Some experience outside of the strictly astronomical will be useful background: a preliminary knowledge of programming in python, IDL, Matlab or Excel will be very useful, but since most of the reductions can be done with freeware written in one of these languages, it isn't absolutely vital.

The course will meet "live" once per week for 2-3 hours with breaks. Since not all of you will be able to attend any or all sessions in real time, the sessions will be recorded and I'll also write material and provide it through the forum. There will be means to communicate by email and chat and exchange questions, comments, and materials.

Spectroscopy is at the heart of astrophysics: the field was actually defined as its application to the study of cosmic phenomena in the last third of the 19th century. The Astrophysical Journal, founded in 1895 by George E. Hale, called itself "An International Review of Spectroscopy and Astronomical Physics". This course is intended to introduce you to the why and how -- why this is so effective as a probe of the universe and how to get involved yourself.

I'll assume you've never done this sort of observation before but that you have some passing familiarity with some of the ideas behind it: light, detectors, telescopes, and the basic structure of matter (that is, that there are atoms and molecules) but not the details. That's a part of the course, how the structure of atoms and molecules governs their interaction with light and how the properties of the environment through which that light passes produces what you detect in the spectrum. You'll have some simple experiments to do on your own with CDs, paper towel tubes, slits, and cellphones, just to get started.

The exercises will include using web resources to identify elemental contributors to spectra, comparisons of sources, and preliminary aspects of data reduction. I'll be supplying a variety of spectra at different stages of reduction and we'll walk through those together to understand how to extract and work with the data.

We'll also cover measurements of profiles, identification of features, flux calibration (a very important part of the business), time series, and many more topics. The aim will always be to understand what your spectra are revealing about the physical state of the things you're observing.

Some instrumental aspects will also be covered, such as the detectors and characteristics of different spectrographs, modes of observing, the comparison between photometry and spectroscopy and the passage between the two, and methods of data reduction.

For those who have spectrographs, there will be observing exercises. For those who don't, I'll supply data and if you have particular sources that interest you, or special topics you want to cover, the format of the course will provide plenty of time for that.


Observational Best Practices

In 2023, a dedicated group of 10 AAVSO members spent months in reviewing the AAVSO International Database and interviewed many observers, with the goals of both finding quality deficiencies in submitted observations, as well as suggesting many ways in which that quality could be improved.  Some of the suggestions fall directly on the AAVSO headquarters staff, such as enhancing the automatic data checking in programs like WebObs.  However, a large number of other suggestions fall under the category of best observational practices.

This course will consider a few of these practices, with the hopes that improving your observational techniques will enable you to make better measurements, and enhance your confidence in the quality of your submitted photometry.  Over the course of about 6 weeks, we will discuss one or more topics per week, showing examples of possible problems, give some suggestions as to how these problems could be solved, and provide daily homework to help you learn the techniques.

The initial course will be carried out on a forum, and geared towards CCD/CMOS observers using photometric UBVRI filters.  If you don’t have your own equipment, or have inclement weather during the instructional period, images taken with AAVSOnet telescopes will be made available.  VPHOT will be used to share images.  The class will be limited to 30 participants.


Observing and Counting Sunspots

Observing and counting sunspots is one of the most important and simple methods for monitoring the activity of our nearest star. This four weeks course will provide the fundamentals of visually and photographically observing, monitoring, and recording sunspots with the aim of involving participants in the determination of the American Relative Sunspot Number (RA). This is an effective index of the solar photospheric activity used by amateurs and professionals worldwide. It has been recorded by AAVSO since 1944 with the purpose of maintaining a long-running and consistent database for the use of solar researchers worldwide.

The course will focus on several topics: equipment, safety issues, basic concepts about sunspot activity, morphology, classification and evolution, recording and reporting sunspot observations both visually and photographically, using software for measuring sunspot positions, basic concepts on solar white light digital imaging and how it can usefully complement visual observations and sunspot counts. We’ll also see how solar probe images can be helpful for the amateur observer’s work.

The course will consider only white light observations of the Sun. They can be carried out with a very modest telescope and a commercial solar filter and do not require any expensive equipment. Narrowband (e.g. H-alpha) observing and imaging are outside the scope of the course, however these topics can be discussed informally for those interested in this kind of activity.

There are no prerequisites for participating. The course is open to everybody, even to absolute beginners in solar observing. However more experienced observers may be interested to join for discussing in detail some of the topics and for contributing to the course with their own experience.


Photoelectric Photometry in the 21st Century

This course will cover the techniques necessary for observers to produce highly accurate variable star observations using single channel photoelectric photometry (PEP).  We will cover the history of PEP technology and its continuing relevance today, as it fills a gap left by CCD and large automated surveys for precision photometry of bright stars.

Equipment and observing techniques will be presented as well as detailed discussions of data reduction and error source identification and correction.  Spreadsheet based tools for extinction, transformation, and data reduction to the standard system will be provided for use in labs using sample observation sets.  Specific techniques applicable to commercially available single channel photometers, such as the Optec SSP-3 and SSP-5 will be covered in detail.

Although this material and the exercises will be based on PEP observations, the underlying theory is applicable to all types of photometric measures, and may prove useful to CCD and DLSR observers who desire a fundamental understanding of photometric measurement.

The course will conclude with a module on designing your own PEP observation program.  Star and observation band selection will be covered, as well as discussions on how to balance the calibration observations needed for high precision with the science observations that are the final results.

The course will use the newly created Photoelectric Photometry Observing Manual as its primary text, but will augment this material with additional readings and tools available on the AAVSO website.

You must successfully complete exercises and weekly quizzes as well as a final examination to pass the course.


Photometry Using VPHOT

This course is designed to teach observers how to conduct photometry using VPHOT, the AAVSO’s cloud-based photometry reduction software. The main objective is to understand “best photometric practices” by independently conducting exercises which utilize VPHOT as the photometry tool. You will learn (1) how to upload and manage your image files, (2) how to create suitable sequences, (3) how to perform differential aperture photometry on single images and time series, (4) how to generate transformation coefficients using TG, (5) how to transform your magnitudes to the standard system, (6) how to save your analyses, and (7) how to submit your results to the AAVSO. You do not have to own a CCD or have your own images since sample images will be provided.

You should complete rigorous daily exercises, and must complete weekly quizzes as well as a final examination to pass the course.

This course is only available to AAVSO members. If you would like to join the AAVSO click here.


Variable Star Classification and Light Curves

This course is an overview of the types of variable stars most often observed by AAVSO observers. We explain the construction of light curves and phase diagrams. We discuss the physical processes behind what makes each type of variable and how this is demonstrated in their light curves. We link these salient features of the light curve to common observing practices for each type. Variable star names and nomenclature are placed in a historical context to aid in understanding today’s classification scheme.

You must successfully complete weekly quizzes and a final examination to pass the course.


Classification variable des étoiles et courbes de lumière

Ce cours constitue une base pour mieux comprendre les étoiles. Il consiste en un aperçu des types d'étoiles variables le plus souvent observées par les observateurs de l'AAVSO. Nous y expliquerons comment obtenir des courbes de lumière et des diagrammes de phases à partir de nos observations. Ceci nous permettra d'en déduire les processus physiques propres aux différents types de variables, leurs particularités, leur activité, leur température de surface effective et bien sûr, comment tout cela peut être démontré grâce aux courbes de lumière. Nous relierons également les caractéristiques de chaque courbe de la lumière aux pratiques d'observation courantes spécifiques à chaque type. La nomenclature des étoiles variables est mise dans un contexte historique afin d'aider à comprendre le schéma actuel de classification.

Nous espérons que vous ne verrez plus les étoiles de la même façon après avoir suivi ce cours.

Vous devez participer aux discussions par écrit et réussir tous les questionnaires hebdomadaires puis l'examen final pour passer le cours.


Visual Observing Basics

This course will use the AAVSO Visual Observing Manual as its primary text. We will cover variable stars, basic equipment, how to make observations and submit data, plotting VSO charts, planning an observing session and many other topics. This course is highly recommended for anyone just starting out in visual VSOing.

The course will last four weeks. There will be an additional two-week period in which to make observations, submit observations, ask questions in the forum and put what you’ve learned into practice. After the six-week period, those who have completed the quizzes, participated in discussions and submitted two positive variable star observations of sufficient quality to the AAVSO International Database will be awarded a certificate of accomplishment along with a badge on your website profile.