We discuss the dominant geometrical aberrations of a grazing incidence reflection grating and new techniques which can be used to reduce or eliminate them. Convergent beam geometries and the aberration correction possible with varied groove spacings are each found to improve the spectral resolution and speed of grazing incidence gratings. In combination, these two techniques can result in a high resolution (λ/Δλ≳104) monochromator or scanning spectrometer with a simple rotational motion for scanning wavelength or selecting the spectral band.