Variable Star Planner

Many years ago I pieced together a BASIC program that would list the next few dates of the minima of a selection of Eclipsing Binaries and a few Cepheids. This worked well for it's time and my skills. I would post the output from that Basic program on the Internet to be used by anyone with an interest to follow the light variation of a star. This next step allows anyone to list future date and times interactively. This is a modification of "The Minima of Algol" javascript by Adrian R. Ashford on Sky and Telescope web page. I have added a selection of popular stars to choose from and some basic information of the star.

Enjoy !

John D. Sabia

Original text from Sky and Telescope web page follows.

The star Algol (b Persei) was the first eclipsing variable star ever discovered, and it's still the most famous one. You can check on it whenever you step outdoors on nights when Perseus is in view.

Algol fades and rebrightens like clockwork every 2.87 days. Its changes are very plain to the naked eye. In the middle of an eclipse it shines dimly at magnitude 3.4 instead of its usual 2.1.

Algol stays nearly that faint for two hours centered on the time of mideclipse, and it takes several additional hours to fade and to rebrighten.

Good comparison stars are Gamma (g) Andromedae to Algol's west, magnitude 2.1, and Epsilon (e) Persei to its east, magnitude 2.9. You can compare Algol's brightness with them at a glance; click on the star chart to see a larger version with the magnitudes of several comparison stars clearly labeled. (For detailed tips on estimating a variable's brightness, see "The Lure of Variable Stars." For information and finder charts for Algol and 11 other inconstant stars, see "The Top 12 Naked-Eye Variable Stars.")

Below is a calculator you can use to predict when Algol or other EB will be at mideclipse. Press "Initialize to today" to view the dates and times of Algol's minima for the next three weeks. Or you can enter any date, between 2007 and 2015 inclusive, to see the dates and times of eight consecutive minima. The times given should be accurate to within a few minutes.

The second row of stars will calculate time of Maxima light of selected Cepheid variable.

EB - Eclipsing Binaries
Cepheids
Please enter a date:
(mm/dd/yyyy)
Computed dates
(mm/dd/yyyy) and
Universal Times
of EB minima or Cepheid maxima:







 Corresponding local
dates (mm/dd/yyyy)
and times of
of EB minima or Cepheid maxima:







Note: local times are based on a time zone offset of
  hour(s) from UT as given by your Web browser.