Photoelectric Photometry Newsletter

Computerized Photometry Project of Summer 1996

by Frank Dempsey

Computerized photometry became a reality for me last summer after I successfully (but not without problems) interfaced my Optec SSP-3 photometer to a portable laptop computer with ACQUIRE software by Robert Jones. I was first inspired by an article in the AAVSO PEP newsletter several years ago by Ken Luedeke who used the same photometer and laptop computer as the ones I was using. In my case, no electricity is available at my observatory location (at the edge of a farm field north of Pickering, Ontario) other than that which I supply from batteries and so being able to use my laptop computer for recording the output from the photometer would be ideal, knowing that another observer had already solved the inevitable problems I could expect to encounter with a new computer application.

When I mentioned my intention of starting this project to Howard Landis and asked if he had any advice, he referred me to Ray Thompson. Ray lives within an hour's drive from my home and he invited me to visit his observatory. He generously demonstrated and explained the ACQUIRE software and the AAVSO and other software used to record the photometer output and then convert it to the AAVSO file format and analyse each observation set for observational error (in situ, on the spot). However, after obtaining the appropriate software and hardware, frustrating bugs persisted that prevented the system from operating properly. After several weeks of e-mail communication with Ken Luedeke, Howard Landis, Ray Thompson and Robert Jones regarding diagnostic tests, potential solutions and encouragment to continue, an internal computer hardware fault emerged as the most likely source of the problems. At this point, the simplest and most economical solution seemed to be another computer. A Saturday of shopping at second-hand computer stores in Toronto with the photometry software on a disk in my pocket turned up a good, low-cost, old (heavy, bulky and relatively small memory) laptop computer in good condition with a good battery that works very nicely for the intended task. Now, photometric data collection is different; the only keystrokes in filing and submitting data are the ones to start and test the software and then to instruct the computer to begin recording the data while looking at the photometer output on the computer screen. The only minor drawbacks to be worked out now are the observatory light pollution (if the night is not moonlit) from the heavily red-filtered monitor screen, and the sluggish computer screen (not to mention short battery life) at winter temperatures much below freezing. Now the freedom from spending many hours typing in the photoelectric observations will allow more time for analyzing and interpreting the variable star observations. I would not likely have completed this project without the valuable photometry-wise assistance from Howard Landis, Ken Luedeke, Robert Jones and Ray Thompson, as well as several computer-wise members of the Toronto Centre of the Royal Astronomical Society of Canada.