The fluorite also serves to correct optical aberrations in these lenses.

In a later design he added a cemented doublet to correct chromatic aberration.

Smaller two-mirror systems can correct aberrations, but they are not suited for imaging spectrometers.

Each surface of the lenses in the corrector creates a degree of freedom to correct optical aberrations.

It is harder to correct chromatic aberrations over wider spectral ranges without further optical complexity.

The two outer elements are positive, one of the inner elements is used to correct spherical aberration, and the other to flatten the field.

It can also correct optical aberration.

This provides an extra degree of freedom in correcting aberration by changing the curvature of the corrector and the secondary independently.

Lens construction includes 1 composite aspherical and 3 ED elements to correct distortion and aberrations.

The design corrects the problems of off-axis aberrations such as coma found in reflecting telescopes while also correcting chromatic aberration.