Jump to content

Banner.jpg.b89429c566825f6ab32bcafbada449c9.jpg

Amateur telescope making


astrosathya

Recommended Posts

Hey Everyone,

I first made a 6" f/10 telescope back in 2002. It was, as everyone called it here "the minimum size you should make". So I went ahead with it. The f/10 was because some gentleman had ground the glass to f/10 and abandoned it in the local astronomy club and the president of which handed to me.

After having used the scope until 2009 (I went to UK for my Masters and bought my GOTO setup at the Telescope showroom I was working.  I am primarily an astrophotographer, but one can never forget ones roots can we?

So, long story short, I am back to grinding a 6' f/8 this time, The FL now stands at 49" (f/8.1). I had finished fine grinding with 1000 grit SiC and moved to 1200 grit SiC but only to realize (after 30mins of grinding) that the seller had incorrectly labelled the powder as 1200 grit. I ended up with large pits all over the mirror and had to resort back to the "actual" 1000 grit SiC. This was yesterday. Now, after about 2 hours of 1000 grit, there are about a dozen pits of varying depth. I think another 30 minutes should get rid of them.

I tried making a polishing tool from White Portland Cement using the mirror as the mold and aluminum foil as separator. Disaster struck as the cement ate away the foil and got stuck to the mirror in the form of a thin layer (thankfully) and I was able to remove all of it by mild scrubbing and later grinding with 1000 grit SiC. The misadventures that I deliberately get into. 😕

Hopefully I can start polishing soon. 

Wish me luck folks. I will post al developments here.

  • Like 6
Link to comment
Share on other sites

Good luck with the mirror.

Whatever you use to support the pitch lap it's probably worth making sure the pitch is of even thickness. So if you decide on thick, sealed plywood the convex surface could be of polyester (grp) resin. The mirror surface used as the mold could be protected with a couple layers of polythene film . Maybe Portland cement isn't so bad if it's well sealed. Or plaster of Paris or dental plaster. Again use polythene instead of Aluminium next to glass.

David

  • Like 1
Link to comment
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
×
×
  • Create New...

Important Information

We have placed cookies on your device to help make this website better. You can adjust your cookie settings, otherwise we'll assume you're okay to continue. By using this site, you agree to our Terms of Use.