Frequently Asked Questions

Sunpath Diagrams

1. Do I need a different diagram if I am on a flat roof?
2. Do the Solar Pathfinder diagrams account for Daylight Savings Time or real solar hours? Or "why doesn't the time of day on the Solar Pathfinder match my watch?"
3. What is the difference between the horizontal and vertical ("south-facing" for the northern hemisphere) diagrams?

Q. Do I need a different diagram if I am on a flat roof?

A. If you are using the Assistant software, it will automatically calculate for whatever tilt angle you enter. If you are manually calculating using only the Solar Pathfinder (without the software), you will need the horizontal diagram to give you the correct percentage of solar radiation.

Q. Do the Solar Pathfinder diagrams account for Daylight Savings Time or real solar hours? Or "why doesn't the time of day on the Solar Pathfinder match my watch?"

A. The sunpath diagrams show real solar time and will not necessarily line up with "clock time". Adjustments need to be made for Daylight Savings Time, what month it is, where you are in the time zone itself, etc. A detailed description of how to calculate the difference between "solar time" and "clock time" is given in the Solar Pathfinder manual.

Q. What is the difference between the horizontal and vertical ("south-facing" for the northern hemisphere) diagrams?

A. The horizontal diagrams are intended for tilts of 0-20 degrees. The vertical ("south-facing" for northern hemisphere) are for tilts of 20-90 degrees. Because the Solar Pathfinder always takes its reading when true south and level, the sun paths for each month and the solar hours on both the horizontal and vertical diagrams are exactly the same for any given latitude. The only difference between the horizontal and vertical diagrams is the tiny numbers written in the half-hour increments. These numbers represent the percentage of solar radiation in each half-hour. The percentages differ slightly based on the tilt angle.

The Solar Pathfinder Assistant software automatically calculates for these differences whether you happen to have the correct diagram in the unit when the picture is taken or not. If you are using the Solar Pathfinder Assistant software, the software will make correct calculations for differences in tilt (and azimuth) no matter what diagram you happen to have in the Solar Pathfinder unit (It makes its calculations based on the tracing.