My first mirror was the standard 6" (about f/10) made from an Edmund kit purchased with Christmas gift money from Christmas 1963 when I was 13. The only guide I had was Geo.Keen's SKYGAZING WITH TELESCOPE AND CAMERA. I knew of no clubs near me, or anywhere, nor Sky & Tel. My parents were not a help or hinderance. They were both artists and utterly lost on this subject. All my Mother said was, "no rouge" from her experiences with jewlery making. So I used Barnesite. Keen's description of the tester and how it worked left me baffled so I traveled from my home in Orchard Lake, Mich. to Dearborn to have it tested at Polaris Telescope Shop (then just split off from Star Liner which moved to Tucson where I now live).