Near-Shade Sun-Path Check

The sun's position comes from the equations behind the NOAA Global Monitoring Laboratory solar calculator, which NOAA says are based on Jean Meeus's Astronomical Algorithms: the declination and equation of time from the date, the hour angle from the time and longitude, then elevation and azimuth, with NOAA's approximate refraction correction. NOAA describes the approximations as very good for years between 1800 and 2100, and notes that observed values may vary from the calculation with atmospheric conditions. NOAA also says its calculator is no longer actively supported; the equations are used as published.

• Obstructions. An obstruction's top sits atan(height ÷ distance) above the array. The sun is behind it when the sun is above the horizon, inside its bearing sector (including a sector that crosses north, such as 350° to 10°) and below that line. The top is treated as level across the sector, so describe a rounded crown or a stepped roofline as several narrower obstructions when the difference matters.
• Dates. The monthly list checks the 21st of each month of the current year every five minutes. The chart draws the solstices and equinoxes on the days the same equations put them, facing the equator, with azimuths in true bearings.
• Time. Times are local standard time for the UTC offset you choose, and daylight saving is not applied. Or choose local apparent solar time, where the sun is due north or south at 12:00.
• Bearings. True north, unless you choose magnetic north. Each bearing then becomes true = magnetic + declination, the relationship Geoscience Australia sets out, using the declination you enter, east positive. Look the declination up with Geoscience Australia's calculator; none is calculated here.
• Row spacing. A row of length L up the slope at tilt β raises its back edge L × sin β. With the sun at elevation α and azimuth γ, and the panels facing γp, its shadow reaches L × sin β × cos(γ − γp) ÷ tan αacross the rows behind it. The widest shadow in your window is the clear gap; adding the row's own depth, L × cos β, gives the pitch. Both are rounded up to the next centimetre and are shade-free for the window you chose, not outside it.

Row spacing on a frame also comes from the racking manufacturer's installation manual, the site's wind region and structural engineering, and the array standard, AS/NZS 5033; the standards index says what each one covers. This check is sun geometry only. Sun position and obstruction geometry alone cannot produce a defensible yield or shading-loss estimate. Diffuse light, weather, the string and module layout and the selected equipment also matter, so use location-specific design software for production estimates. This check shows only when the sun is geometrically behind an obstruction, and it does not judge whether module-level power electronics are worth fitting.

Location is the latitude and longitude you type, or the device's location when you tap for it. It stays in this page, is never stored or put in the address, and is left out of a saved result unless you tick it in. To record the roof's direction and pitch, use the Roof Direction & Pitch Check.