Visibility of Astronomical Objects

Calculations using Java Script

Java Script pages providing calculations using the algorithms of Bradley E. Schaefer
given in the Nov 1989, and May 1998 issues of
Sky and Telescope Magazine.
Pages Constructed by Larry Bogan
Comments to L.Bogan

The following three pages will calculate limiting magnitudes for eye and eye + telescope, plus the counts on a CCD + telescope for a given magnitude.

Magnitude Limit of Unaided Eye Observations
Input factors that determine limiting magnitude are: Lunar position and Phase, Solar Position, Humidity, Temperature, Age, Position of the Star, Color Index, etc.
The output of this calculation also includes atmospheric extinction, sky brightness, and magnitude limits in the five wavelength bands UBVRI.
Magnitude Limit of your Telescope
Input factors that determine limiting magnitude are: Sky brightness, Experience, Aperture of Telescope, Cleanliness of objective, Atmospheric Extinction, Zenith Angle, etc.
Star Counts for your CCD Camera on your Telescope
The inputs in this calculations include most of those in the calculations of the unaided-eye limit and the telescope limit. In addition, the specifications of the CCD and filters can be changed from the default values. The output is sky counts and star counts given you photometric apertures and seeing disk.


Netscape and Internet Explorer both include interpreters for the Java Script Language. This 'script' includes mathematical methods that allows it to do almost any calculation the BASIC, PASCAL, C, or other programming languages will do. In addition Java Script interacts nicely with HTML documents and provides a user friendly environment. Input and output of the 'programs' in Java Script are with HTML forms. Default values can be programmed into the text boxes of forms to make entry easy.

Java Script programming language is available to everyone with a modern browser.

Larry Bogan