The mirror was then ground against the tool, and the contact areas were marked with a felt marker so show where contact was made. This was after a few minutes of grinding. Contact occurred after about an hour, and the glass was ground for another couple of hours to be sure of spherical contact. The mirror was then ground conventionally. A typical ATM session in the driveway at the Baldwin Optical Shop.
Grinders are outside, inside are polishers.
This was October 1999. Sergio Avalle grinding on the SHS scope at the SAS ATM session.