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Making a glass optical dome for all sky camera
Members of the ASV's instrument making group have started building a batch of all sky cameras, myself among them, and I thought I challenge myself at making a glass dome for mine, rather than use a commercial plastic one.
Just recently I had built a small electric kiln so I started experimenting with glass slumping. After a number of trials I came up with a two stage procedure to get a roughly hemispherical glass blank that could be ground and polished into a good optical dome.
At the first stage I used a terracotta dish to slump a 99mm diameter glass disc to a concave shape.
At the second stage I slumped the preformed glass onto a 63mm stainless steed dome.
The main problem is that, while the inside is quite spherical, the edge of the glass has thickened to almost 5mm, and the center is 2.7mm thick, down from the original 3mm.
I will try to grind the outside spherical and achieve a wall thickness of at least 2mm.
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