NRC TIS NEWSLETTER
TIS NEWS - Ottawa, 2002 April 26

HIA solar and lunar tables prove popular with public

Planning a sunrise fishing trip in June? Wondering when the next full moon will appear? For 30 years, Canadians from coast to coast have contacted the Herzberg Institute of Astrophysics when they need precise information about solar and lunar events.

Since 1997, this service has been available on the Web. HIA's sunrise/sunset and moonrise/moonset tables provide coverage for more than 300 Canadian and 100 international communities. But the data they offer still generates plenty of calls to the Centre of the Universe interpretive program. And all the really tricky requests end up in the inbox of radio astronomer, Dr. Jacques Vallée.

"I get phone calls from lawyers who claim the sun interfered with their client's driving and caused an accident," says Vallée. "I also get calls from conservation officers to confirm that somebody was killing animals after sunset, which is not legal in certain provinces. These people require a formal certificate. They'll find the information they're looking for on our Web site, but a judge won't accept it as is. So they ask us to print it, sign it, and send it to the judge."

For processing legal requests, HIA charges $300, which goes toward public outreach programs. Other requests are handled free of charge, such as those from calendar makers who need to know the monthly dates of the four moon phases, Islamic organizations who need to know when the new moon arrives to launch the month of Ramadan, or scientists who need accurate day length data for agricultural experiments.

HIA's program for solar and lunar tables were created in 1970 by astronomer Chris Aikman, now retired, who has just landed a contract to update it with a 30-year guarantee. Although the Institute's Web site is not the only one in Canada to offer sunset/sunrise information, its tables are the most precise. At present, they are accurate to within two minutes but the newer version will reduce the margin of error to 30 seconds.

"Ours are more accurate because they take into account such things as a range of physical processes (refraction, precession, oblateness, etc.), tidal effects and the height over the observatory. I guess that's the reason why lawyers come to our site," says Vallée.

In responding to the trickier questions over the past six years, Vallée has found the tables have an outstanding record. They've never been proven wrong outside their stated accuracy, despite the claims of some error-prone customers.

In addition to the requests concerning solar and lunar events, "we also get occasional inquiries when somebody sees a brilliant light in the sky at night on a particular date," adds Vallée. If the reports sound credible, HIA passes them to the Canadian Space Agency's Meteorites and Impacts Advisory Committee (MIAC), also known as the Canadian Fireball Reporting Centre.

A five-minute exposure taken during the Leonid meteor shower (18 November 2001) shows a fireball traveling at speeds up to 70 km per second, and the smoky trail drifting in high altitude winds.

A five-minute exposure taken during the Leonid meteor shower (18 November 2001) shows a fireball traveling at speeds up to 70 km per second, and the smoky trail drifting in high altitude winds. (Photo credit: Astronomy Picture of the Day)