Rowland Type Concave Grating

Rowland type concave gratings have grooves that are straight and equidistant.

This type of concave grating diffracts the spectrum onto a Rowland Circle which is defined as a circle where the diameter of the circle is equal to the radius of curvature of the concave grating.

Rowland type concave gratings suffer from astigmatism but other types of aberration are small.