

Hap Rho
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Cartesian, cylindrical, and spherical coordinate systems each describe positions in three-dimensional space with variables matched to symmetry. Cartesian uses three linear coordinates x, y, z. Cylindrical replaces the horizontal plane with radial distance ρ and angle φ while keeping z. Spherical uses a single radial distance r, polar angle θ, and azimuthal angle φ. The image provides the standard conversion formulas between all three pairs of systems. These conversions are routinely applied in GPS receivers, which translate satellite data from spherical coordinates into Cartesian coordinates to determine a user's exact location on Earth.

Every lunar eclipse has a selenelion phase somewhere on Earth. The reason they seem rare is you must be near the terminator to see the selenelion phase. Whether they are "upside" down or not depends solely on whether your viewing from the morning or evening part or the terminator. Diagram¹ ht: @Roohyfnol ——— ¹ not to scale

















