Another great result, Raymond. Seems you have something of a "Midas touch",having such success with these large fast projects.
Have managed to do the regrind and repolish work on the 33". This time its come through "pit free", as well as free, (as far as I can tell) from astigmatism.
Like to comment: The two mirrors just polished, (25 and 33), are the first I have done using recycled pitch, (Gugolz). I had around 4kg of old gugolz, retrieved from the cleaning up of old laps and channel cutting. As new Gugolz is expensive, I "took the plunge", by melting down and reusing the old. Was a little concerned that there could have been abrasive contaminants in the recycled product, which would have (if present), been a source for scratches. My concern was unfounded as both mirrors came through their respective polishes scratch free.
Did note that the recycled pitch (#55 Gugolz [when new]), was more like #73+ hardness. Still did the job, even though my working temperatures have been around 7-12deg C.
Adding some pics of current polished 25 and 33 to show size comparisons. Also comparison 3" to 33". (My first reflector (1960/61) was a 3" Newt). The 33" mirror (when completed and coated, will gather 121x the light of a 3"). Also pictured (far right), comparison 6" to 33". (6" size of the first mirror I ground).
|