Bent Larsens astro photos

My first mirror grinding

Object: Grinding a 8" mirror to F4,5

Project started november 2013. Hopefully I'll have a new telescope in an year

The grinding stone. A piece of a granite kitchen table

The mirror after the first day of grinding

The grinding with mesh #80

and a lot of hard work.

During the grinding it is very important to check if the mirror have perfect contact with the tool.

Marking the mirror with squares all over, and the grinding will tell, if the mirror have full contact with the tool. On the picture above, it is clear, that there is not equal contact every where on the surface. So on this pucture the mirror and the tool are not perfect spherical. Later on in the grinding, the markings disappeared after just one wet.

Finally on the 1th of January 2014 I finished fine ginding with 9 ┬Ám Aluminiumoxide. I now had to prepare for the polishing process.

Starting to prepare the pitch lap by melting the pitch. This is quite a messy process, so everything is covered in alu wrap.

First I tried to make the tiles on a rubber surface, but with no luck, so I poured the melted pitch directly over the lap base (made of plywood), and pressed the chanals into the half melted pitch.

The small facets on each tile were made by hot pressing with a small plastic net covering the pitch lap.

Finally I was ready for the first cold press before my first polishing session.

As you can see, there is good contact between the glas and the pitch lap. And after first polishing session, I'm very impressed. It's extremely hard to polish but the result comes fast. After one session, there is a huge improvement on the mirror.