Ask what actually changes with the input
A useful test is simple: if you change the time or location, does the geometry change? A calculated sky chart should respond to the observer’s moment, not merely swap a caption under a fixed star field.
Sources: U.S. Naval Observatory — Computing Altitude and Azimuth
Sky is broader than stars
Planets, horizon geometry, orientation, constellation lines, labels, lighting, and other layers may all be part of the view. “Sky chart” leaves room for those systems without implying that every output is a conventional astronomical atlas.
Search language can stay flexible
Someone searching for a custom star map may still be looking for this category of object. Spatial Press uses familiar search terms where they help discovery while keeping the technical claim narrower: a chart tied to a real time and viewpoint.