Every Geoptik instrument is delivered with a final optical correction certificate which is measured with special optical machinery. This written certificate guarantees the real level of correction on the wave front and mirror surface. Furthermore, each instrument identity is supplied with photographic test controls. This procedure certifies it's correctional identity.

Fig.1 FOUCAULT TEST Primary mirror CENTER	Fig.2 FOUCAULT TEST Primary mirror 50%	Fig.3 FOUCAULT TEST Primary mirror EDGE
Fig.4 RONCHI TEST Primary mirror	Fig.5 INTERFEROMETRIC TEST Secondary mirror	Fig.6 REFLECTANCE TEST

The Foucault test is particularly precise and refined. During testing, the mirror shows light and shadows symmetrically divided in two vertical halves; every half shows light and shade effects in retrospect to the other half. Any asymmetry between the left and right of the mirror determines the optical defected surface. During the Ronchigram test, the image reflected on the mirror provides objective answers on probable defects of the lens. Interposing a flat glass, it's possible to observe the Ronchi Reticle even on the secondary Newtonian optics (see photo 5). The regular disposition of the interference lines, is proof of the high quality optical workmanship. Such high levels of correction are difficult to obtain on secondary Newtonian mirror optics.