Schwarzschild telescope

The Schwarzschild telescope is a reflecting telescope with two aspherical concave mirrors. It was developed by Karl Schwarzschild and named after him.

Construction

Schematic representation of the "Schwarzschild telescope"

Due to its structure, it is free from the aberrations of coma and spherical aberration and has no field curvature. The focus is inside the telescope, so it is only suitable for photographic purposes^[1] unless a diagonal mirror is included. A telescope of this type with a 60 cm primary mirror was built by Indiana University in the 1930s.^[2]

Couder telescope

A variant of this is the Couder telescope, which eliminates the astigmatism image error, but has a field curvature.^[3][4]

References

1. Nariai, K.; Iwamoto, H. (2005). "A variation of Schwarzschild telescope: golden section solution with two concentric spheres and its extension to finite distance solutions". Optical Review. 12 (3): 190–195. Bibcode:2005OptRv..12..190N. doi:10.1007/s10043-005-0190-z. S2CID 119557866.
2. "The Work in Astronomy at Indiana University" (PDF). Indiana Alumini Magazine. 1940.
3. Couder, A. (1926). "Sur un type nouveau de télescope photographique". Comptes Rendus. 183: 1276–1279.
4. Willstrop, R. V. (1984). "The modified Couder telescope". Monthly Notices of the Royal Astronomical Society. 209 (3): 587–606. doi:10.1093/mnras/209.3.587.