#3182: Telescope Types

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[The comic contains cross-sections/diagrams of 13 different types of telescopes, each with a small eye representing the observer and shaded areas representing the path of light, with darker areas indicating where light overlaps itself. The light originates from the left in all but the Liquid Mirror and Geological diagrams.]

[Prime Focus: A telescope that contains a concave mirror at one end, which reflects and focuses a column of light directly to an observer within the telescope.]

[Herschelian: Similar to Prime Focus, except the mirror is angled such that its focal point is outside the telescope, along with the observer.]

[Newtonian: Similar to Prime Focus, although there is a smaller angled mirror that changes the direction of the light by 90° after being focused so that the focal point is outside of the telescope.]

[Galilean: Rather than being reflected, the light is refracted by a convex lens and focused until it hits a concave lens at the other end, where the observer is.]

[Keplerian: Similar to Galilean, although the light narrows to a point and effectively "flips" before being straightened out by a second convex lens.]

[Gregorian: Similar to a Prime Focus telescope, though the light is refracted a second time by a small concave mirror slightly after the focal point and exits through a gap in the first.]

[Cassegrain: Similar to Gregorian, though the second mirror is convex and slightly in front of the focal point.]

[Cardboard Tube: A simple tube that allows only a small potion of light in, which is then seen by the viewer.]

[Kaleido: A tube with several small pieces of some material at one end, which light passes through and is then repeatedly bounced around in a reflective inner tube.]

[Liquid Mirror: Similar to Prime Focus, except the mirror is vertical and made of liquid being rotated at a constant speed by a motor underneath. A drinking straw leads out of the liquid and toward a small closed mouth.]

[Narcissian: Similar to Prime Focus, except the light is emanating from Cueball, who is standing ~4m away from a Cueball-sized mirror. The light is being refracted directly into Cueball's face.]

[Gravitational: A small black hole is in the middle of the telescope, positioned just right to warp two streams of light coming around it directly to the observer.]

[Geological: Similar to a Newtonian telescope, except the primary mirror is replaced by a small television labeled "TV playing The Core (2003)."]