Why are extremely fine abrasive powders used to polish telescope lenses and mirrors?

Extremely fine abrasive powders are essential in the manufacturing of telescope lenses and mirrors because they are required to produce scratch-free, ultrasmooth surfaces.1

In the production of optical components, the process begins with grinding or lapping to achieve the final form using coarse abrasives. Once the desired shape is generated, the surfaces must undergo fine grinding and polishing to reach the high level of precision necessary for astronomical instruments. Polishing is a slow, meticulous process where the glass is oscillated against a tool covered in a polishing agent, such as wet rouge or other mineral oxides.2

Using progressively finer grades of abrasive ensures that the surface is refined to a state where it can form images of acceptable sharpness. Because even minor imperfections or scratches can cause intolerable blurring of an image, these fine powders are critical for achieving the high-quality finish required to resolve fine details in distant objects.231