Ronchi Gratings Calculator

This page represents a simple online tool for Ronchi null-test gratings calculation. The gratings can be used in the testing process of astronomical telescope mirrors as a quick and easy quality check. Please, select the grating's parameters and then click the calculate button. From the download button, you can save calculated grating as an 2000x2000 pixels png image. For more info, see the explanation below.

NOTE: The calculator implements an original method. The theory behind is shown on our astronomical mirror testing methods description page. You can also read more about the history of optics and telescope making. Here:

• Gratings can be either linear or circular. Linear gratings are projected as a sequence of equidistant straight bands on the mirror when its surface is figured and takes its final geometric form. The circular gratings project as equally spaced concentric circular bands.
• Gratings can be either positive or negative. The last ones are with reversed black and white bands. If the contour drawing has been chosen, this field has no meaning.
• Gratings can be plotted as solid color bands or contours only.
• The number of the same color bands can be between 1 and 30.
• Mirror diameter is expressed in mm.
• The paraxial radius of curvature must be greater than the mirror diameter. Radius is measured in mm.
• A surface eccentricity is a number between 0 and 2. For a sphere, it is equal to 0. For an ellipse, it is between 0 and 1. For a parabola, it is 1, and for a hyperbola, it is greater than 1.
• Light source distance must be a positive number. It is measured in mm from the paraxial center of the curvature towards the mirror.
• Grating distance must be a positive number. It is measured in mm from the paraxial image of the light source towards the mirror.

The calculated Ronchi null-test gratings can be printed by lithographic technology or printed in a large size and then photographed in final size on a contrast fine-grained diapositive film.