[ATM] Ross Null tester

[GFPhoto]

I've been working on a Ross Null tester to complement regular knife edge Foucault and autocollimation. 

http://www.gfphoto.com/atm/rossnull/Tester%20detail%205.jpg
http://www.gfphoto.com/atm/rossnull/Tester%20detail%206.jpg
http://www.gfphoto.com/atm/rossnull/Tester%20detail%201.jpg
http://www.gfphoto.com/atm/rossnull/Tester%20detail%203.jpg
http://www.gfphoto.com/atm/rossnull/Tester%20detail%204.jpg
http://www.gfphoto.com/atm/rossnull/Ross%20D90%20new%20diff%20s.jpg

The light source is a Melles Griot class II HeNe laser I found at the scrap yard, powered by a 15.6V DC power supply from Surplus Shed. 

The PCX lens was a really nice swap table find at Stellafane--part of a commercial order from the early '80's (Thanks Paul). A little over 6" diameter. 

My son made the holder so the front is level with the lens surface so measuring to the mirror is easy.

The base is also a scrap yard find from I guess some piece of lab equipment. A bit of overkill but it weighs about 20 lbs so nice and stable and the movements are smooth. I machined the prism holder from a piece of plastic rod so that it would be a friction fit on the front of the laser and be able to turn for alignment.

There's a 1mm thick diffusing ground glass (both sides) after the prism and then the screen.
With the ground glass and screen removed there's a dot for alignment.

http://www.gfphoto.com/atm/rossnull/Tester%20detail%207.jpg

Gary