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600 mm f/3,3 Meniscus Mirror

Advantages of the same overall thickness: Enhanced stiffness at same weight. More uniform cooling of middle and edge.
Disadvantage: Much more effort, to grind the back side and support the mirror during grinding and polishing
See intruduction in Cloudy Nights and in the German forum Astrotreff here and here

click on the images to enlarge

The meniscus was milled out of the full material, as slumping (heating and bending to shape in the oven) was no accessible option to me.

Generating the concave front side with a grinding machine on a jig out of 600x34,5 mm Supremax blanks

Video (5 MB)

Generating the convex back side. Grinding over the edge produces chips in the glass

Video (5 MB)

Protective mask, ear protection and a strong fan, that blows the dust away from the body

Fitting the concave frontside on the convex backside to grind out the residuals from the rough machine generating.

Diameter: 600 mm
Same averall thickness (meniscus shape): 21 mm
Weight: 13,3 kg
Focal length: 2.000 mm
Approx. 8 kg glas was transformed to glassdust

Video mirror on mirror grinding with K180 (11 MB)

Grinding with #180 with the 40 cm granite tool

Video Tool on mirror grinding with K180 (10MB)

Grinding with #320 and Microgrit 25 my with the 40 cm granite tool

Video Tool on mirror grinding with K380 (18MB)

Video Tool on mirror with Microgrit 25 my (15MB)

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