To day I write some documentation on what telescope I want to make, the supplies which have to be used and how the mirror will be tested.
The Target:
10″ mirror (precisely is the diameter 254 mm), f:5,6 focuslength: 1456 mm. The mirror have to be mounted in a Newtonian with dobson-mounting.
Supplies:
10″ pyrex (260 x 36 mm)
Silicon Carbide 60 grade 2 lbs
” ” 80 grade 1lb
” ” 120 grade 1/2lb
” ” 220 grade 1/2lb
” ” 320 grade 1/2lb
Emery 125E grade 1/4lb
” ” 50E grade 1/4lb
Cerium Oxide 1/8lb
Pitch (Svensk kronebeg)
Tiles
Gypsum
Method or progress of work:
Testing blank for error
Make tool for rough grinding
Rough grinding with carbide 60, 80, 120 og 220
Control sagitta and curvature
Make tool for fine grinding
Fine grinding with Carbide 320, Smergel 125E og 50E
Control sagitta and curvature
Make tool for polishing
Polishing with Cerium Oxide do also control by Foucaulttester
Polish and figurering
How to make test and control:
Template made in plastick, curvature marked by a calipers/dividers, radius of curvature = 2 x focuslength.
Sagitta(S) is the curvature depth in the center of the mirror.
S = R – squareroot(R^2 – r^2) R = radius of curvature = 2 x fokuslength r = radius of mirror.
S = 2912 – squareroot(2912^2 – 130^2)
S = 2912 – 2909,0967
S = 2,9033 mm
Foucaulttester is constructed about a lightsource (a virtuel star) and a screening which do it posibly to analyze the surface of the mirror.