Why are some of the output fields blank?

If the required inputs are not filled in with valid data, the outputs that depend on them are blank. But as many outputs are calculated as possible for a given set of inputs, even if some are left empty.

How accurate is the program?

Good question! The angular calculations are probably accurate to at least one arc-minute (1/60th of a degree), and the results have been checked against many published sources. Further work is underway to better gauge the precision of the calculations, and I'll list the results of that research here when it's complete.

May I copy your calculations?

The program and its design are copyrighted, but I don't mind if you use my calculations as a reference in writing your own. Please do not copy the program or page design wholesale and reproduce it. If you have a question about what's reasonable to copy, just ask.

What if I want to calculate values for years other than those in the pull-down menu?

Just use the default value of 2000. The year input really only affects the declination and equation of time calculations, and even those not much at all (a fraction of a minute at most). So if you're looking for altitude and azimuth angles, you can more or less ignore this input unless you're looking for very accurate results.

Is there a version of SunAngle for PalmOS?

Thanks to Greg Bell (sunangle_palm@yahoo.com), SunAngle has been ported to PalmOS, and is available on Greg's SunAngle for Palm web site.

What is your source for these calculations?

The basic solar angle calculations are from a variety of sources, and I would suggest looking in the ASHRAE 1993 Fundamentals volume for more information, as well as the book by Dr. T. Muneer mentioned on the notes page.

Do you know of a source of other building-related solar energy programs?

Check out the building energy tools directory at the U.S. Department of Energy.

What's up with the error message "WARNING: longitude differs from time zone meridian..."?

This means that you have specified a longitude that isn't anywhere near the time zone meridian that would be expected for that value. For example, if you're at longitude 120 degrees West, and you leave the "Time Zone" input set to its default value of "GMT", the program will detect that there is 120 degrees of difference between your local longitude and the time zone meridian, and alert you that one is incorrect. This error message most frequently appears if you have the longitude "East/West" pulll-down menu set incorrectly.

Can you write a custom program for me?

Yes...I enjoy writing custom solar angle and similar calculations and am happy to provide a quotation for consulting work. I can also customize a version of SunAngle to meet your specific needs. If you're interested, please write!