The map tells you *where* the sun will be. It cannot tell you whether a tree, a ridge or an apartment block is in the way, or whether your lens can hold the whole scene. Two tools close that gap: AR sky view and the Field of view calculator.
Tap AR sky view from the Planner. The camera opens with sun, moon and Milky Way core markers drawn over the live image at the positions they will occupy at the time you set on the slider. Move the phone to scan the sky. Where the sun marker sits at your planned time is exactly where the sun will be.
How it works: the phone's motion sensors give its pointing direction as an altitude and a compass heading; the app converts the planned positions into the same coordinates and draws them. The compass is the weak link. Phones use a magnetometer, which is thrown off by cars, steel railings, tripod heads and even the camera on a tripod next to you. If the markers seem a few degrees off:
Tap the shutter to save what you see — the camera frame with the markers, time and bearing burned in — to your photo library; it is the fastest scouting note there is. If a body is out of frame, an arrow at the edge tells you how many degrees to turn.
Use AR on-site during a scouting trip in daylight. You can stand in the exact spot, set the slider to tonight's core window, and see whether the galactic centre will clear the treeline.
In Tools › Field of view, choose your sensor format and focal length. The tool returns the horizontal, vertical and diagonal angles of view. Two things this answers immediately:
Will it fit? If the sun sets 40° to the left of the peak you want in frame, you need at least 40° of horizontal coverage plus margin — a 35 mm lens on full frame gives about 54°, so it fits; a 50 mm gives about 40° and does not.
How big will the moon be? The moon is about half a degree across. On a full-frame sensor with a 200 mm lens (10° horizontal) it is one-twentieth of the frame width — clearly a disc. On a 24 mm it is a dot. The Field of view tool lets you work this out before hauling the long lens.
The angle of view depends on both focal length and sensor size, which is why the sensor picker matters. A 24 mm on APS-C behaves like a 36 mm on full frame.
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