When to Use the Atmospheric Refraction Sunset 3D Explorer
freetoolonline.com editorial team
Open the Atmospheric Refraction Sunset 3D Explorer when you want a hands-on answer to why the setting Sun looks flattened, sits higher than its true position, and can briefly flash green.
Sessions this explorer fits
Students and teachers introducing atmospheric refraction, readers curious why "sunset" is defined the way it is, anyone wanting to understand the physical cause of a green flash before trying to spot one, and readers who want to see the Sun's true and apparent positions separate all get a direct answer here.
When atmospheric refraction is not your real question
Skip this explorer if your real question is about the wider civil, nautical, and astronomical twilight bands that span the much larger 0-18 degree range below the horizon; those graded sky-darkness stages live on the Twilight Types 3D Explorer, which renders how the whole sky dims after the Sun is gone rather than the sub-degree optical bending of the solar disk itself. It also does not model the color-scattering path length that reddens the low Sun - refraction here means the vertical lift and squash of the disk, not the reddening. Once you are ready to move the refraction sliders yourself and compare true against apparent altitude, the step-by-step guide walks each control and readout in order.
The best moment to open this explorer is the last minute before the Sun touches the horizon, because that is when refraction is strongest - it lifts the whole disk by roughly 34 arcminutes, slightly more than the Sun's own width, so at the instant you see the lower edge kiss the horizon the true Sun has already dropped fully below it. Use it too when you are checking why a photo shows the disk squashed into an oval: the lower edge is bent up more than the upper edge, and the explorer lets you exaggerate that difference to see the shape form.
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