Surface Error

Foucault test is very popular for amateure' making their telescope to measure mirrors' error. Foucalt test is geometrical ray trace test, not wave optical. To know how accurate Foucalt test is, I made Foucault test simulation and compared it with PSFs of mirrors with error.


8-inch Newton telescope
Calculation devision of mirror : 50x50
Error : adding sin curve on the mirror
Pin hole size : 0.2mm&0.3mm
Reference wave length : 500nm
PSF calculation : Diffraction integral of wave frontBR> Time calclation was approximately 3 hours(by Celron450)

Foucault test (φ0.2mm)、From left , 1/4、1/8、1/16、1/32、1/64λ added error

Foucault test (φ0.3mm)、From left 1/4、1/8、1/16、1/32、1/64λ added error

PSF images、From left 1/2、1/4、1/8、1/16、1/32λ added error

Reflection error is produced twice of the surface error.
Depending on pin hole size, the accuracy change. Using 0.3mm pin hole, I say that Foucault test detects 1/16 wave error, which means that the maximum surface error is 1/8 wave.

How can we see Jupiter with those results ?

From left 1/2、1/4、1/8、1/16 wave added error

July 14th, 2000 in English page