Edit: I now use actual glass domed lenses..
But in a pinch this is how I use to do it..
Polystyrene plastic works great for the lenses. Can be a bit tricky to cut but with a little effort and care it does the job quite well..
It's also has a nice thickness to it but again not to thick that it can't be cut with some scissors..
Cut off a square big enough for both inserts and make sure to keep the plastic covering on..
Us the inside circle of each to get ur size and trace with a sharpe over the removable plastic..
Then start cutting but you do have to be careful not to splinter the plastic. Start a little bigger than the insert and work backwords until it fits..
Third times a charm..
I also like to add a reticle. I found these just by googling "Star Wars reticles" and it's the first ones that come up. If anyone knows who gets the credit I'm more than happy to give it.
Also if anyone knows of any HQ reticles that would also be great. These do the job pretty good as they are though. Just had them printed up at a local Office Depot on thin plastic..
Next I took the plastic covering off and attached everything as pictured..
Now just repeat the process for the front lens and u should be good to go..
End of my lense build edit:
It's late so I had to mess with the exposure a bit but I don't think it takes to much away. I still have to add the physical weathering..