History & Operating Highlights of the AAVSO Photoelectric Program

By Howard J. Landis, (former) AAVSO Photoelectric Photometry Committee Chair

Presented at the opening session of the AAVSO's second European meeting, held in Sion, Switzerland, May 26, 1997.

The AAVSO Photoelectric Photometry Program began in 1983 with 3 observers who in that year contributed 219 observations on 28 stars. Standards were established on how to observe-i.e., taking three measures of the variable and one of a check star to monitor the constancy of the check star. These standards have not changed and the reduction program used today is the same one we started with. We do not archive observations with a standard error of greater than 0.02 magnitude.

To date, we have 18,757 observations in the PEP Archive. Over the years, 37 observers have contributed data, and 16 are currently active. While most are US observers, there are two Canadians, one Italian, one Dane, one German, and one South African. We have been producing data at a rate of 2500 to 2900 observations per year.

As Chair of the committee, I communicate with prospective observers, lead them through the training as necessary to help them become successful PEP observers. Then I watch over the data as they come in, and if I see an apparent problem, I communicate with that observer and explain what needs to be changed. I have developed many productive friendships over the years.

The AAVSO photoelectric photometry program catalog contains 70 stars, including many classifications of small amplitude variables. In addition, there were originally 4 Be-type stars in the catalog; 4 more have been added this year. All observers are free to observe any star in the catalog, therefore some stars will have observations from many observers. The data are not as uniform as they could be if only one observer observed each star, but we feel it best to allow this. We get more interest in observing if observers are free to take on what is most interesting to them. The PEP finder charts have all the necessary data on position, color, and magnitudes for these stars.

Dr. John R. Percy started the Small Amplitude Red Variables program, in which he assigns one or more stars to individual observers. Only one observer will observe each star, resulting in cleaner curves for these small amplitude stars. So far over 100 stars have been investigated; some now have been assigned a variable star name, and some are now classified as non-variable. Most of these stars were selected from the questionable variables in the Yale Bright Star Catalogue.

I created a data reduction program early on, further developed by AAVSO Headquarters, which is used by the archivist and many of our observers. A data entry program is provided with which to create data files which will run in the reduction program. A program to calculate epsilon V is also available which uses the RED-BLUE star pair method. We have a few finder charts for these stars. Programs are available at no cost to AAVSO PEP observers.

Most observers take the data at the telescope manually, type them into a computer, send them to me, the archivist, by means of computer disk, or via E-mail. Some leave the data in handwritten form and mail them to me or to one of my assistants, Kenneth Luedeke or Jim Wood.

Most observers use the OPTEC SSP-3; a few use the SSP-5. Five observers take the digital output data from the SSP-3 or SSP-5 and feed it into a game port on a PC. With (freeware) software written by Bob Jones, a file is created that is a complete observation without manually writing down anything. (Unfortunately, the data are not recorded in AAVSO standard format and must be converted by a program I wrote before they can be run through our reduction program.) This operation does save the observer a lot of time and those who use it strongly recommend it.

Dr. John Percy is our professional mentor and is the editor of the AAVSO Photoelectric Photometry Newsletter, which is published 3 or 4 times per year. It is free to AAVSO members for the asking and provides much encouragement to PEP observers.

The AAVSO gives an award to PEP observers who have submitted over 1,000, 2,500, or 5,000 PEP observations.

Some papers published using AAVSO PEP data include:

• Information Bulletin on Variable Stars (IBVS) No. 3479 (1990), "Photometry of the Eclipsing Binary DHK11 = SAO 23229",* by D. B. Williams, H. J. Landis, and D. Pray [*star discovered by Daniel H. Kaiser]
• IBVS No. 3620 (1991), "Photoelectric Photometry of the Carbon Star V614 Mon," by Rick Wasatonic
• IBVS No. 3673 (1991), "Photoelectric Photometry of FP Virginis," by Rick Wasatonic
• IBVS No. 3739 (1992), "The AAVSO Photoelectric Photometry Archive," by H. J. Landis, J. A. Mattei, and J. R. Percy
• Publications of the Astronomical Society of the Pacific (PASP), Vol. 101, pp. 893-898 (October 1989), "The Photometric Variability of EU Delphini," by J. R. Percy, H. J. Landis, and R. E. Milton
• PASP, Vol. 106, pp. 611-615 (June 1994), "Photoelectric Surveys of Suspected Small Amplitude Red Variables. III. An AAVSO Photoelectric Photometry Program Survey," by J. R. Percy et al. (18 authors)
• Astronomy and Astrophysics, Vol. 191, pp. 248-252 (1988), "Photoelectric and Visual Photometry of P Cygni," by J. R. Percy et al. (14 authors)
• Astronomy and Astrophysics, Vol. 246, pp. 441-446 (1991), "Photometry of Yellow Semiregular Variables: rho Cassiopeiae," by E. Zsoldos and J. R. Percy
• Journal of the American Association of Variable Star Observers (JAAVSO), Vol. 2, p. 38ff (1973), "A Photoelectric Light Curve of X Cygni," by H. J. Landis
• JAAVSO, Vol. 23, p. 123ff (1996), "Photometry of EU Delphini in V and I," by R. R. Thompson
• JAAVSO, Vol. 25, p. 14ff (1997), "Be Stars in the AAVSO Photoelectric Photometry Program," by J. R. Percy, A. Desjardins, and D. Yeung