Cleaning filtered rear aperture?

WarWagon · Post by **WarWagon** » Fri Dec 09, 2011 3:07 pm

I've got a Gehmann adjustable rear aperture with colored filters, which over 10 years of use, has developed a haze over the filters themselves. Is there a way to disassemble and clean these at home?

mtncwru · Post by **mtncwru** » Fri Dec 09, 2011 5:54 pm

Yes, there is. The manual that comes with the iris should detail takedown instructions, and once it's apart you can clean it with some canned air and a microfiber cloth. When I took mine apart to clean it I wore medical-type gloves and was extremely careful not to touch the filter elements themselves. The only real tricky part was reassembly, and then only to make sure you get the color filter wheel back in the right orientation, so the colored dots on the wheel line up with the filters being applied.

KennyB · Post by **KennyB** » Fri Dec 09, 2011 6:51 pm

Checking each filter using a Jeweler's Loupe or other magnifier will show the crud and smears. It's amazing what your optics can pick up over the years without you realizing...

Be very, very careful dismantling it though.

WarWagon · Post by **WarWagon** » Fri Dec 09, 2011 6:54 pm

Thanks, all. I was doing it right (thought I wasn't), but that rear cover plate was hanging on for dear life. I ended up having to put it in a vice to get it off. Marred up the locking ring a bit, but there was no way it was ever coming off with the original wrench.

Those filters were FILTHY, looked as though someone had thrown a plate of spaghetti noodles on them. I thought they were scratched, but it all came off with an optics cloth, and went back together with no issue. Filters look good as new looking through the aperture now, no more haze!

xnoncents · Post by **xnoncents** » Fri Dec 16, 2011 5:10 pm

OK, now you really got my interest. I have a Anschutz rear filter sight with polarizer that really needs an anti haze cleaning. The instructions that came with it are beyond a joke (even the German part does not cover dismantle). Does it come apart the same as the Gehmann, and can you tell me how exactly do you disassemble this? Any help is greatly appreciated. Also, what do you mean when you say optics paper? Do you mean the lens tissue that is usually used for camera lenses. Any lens cleaning solution used?

WarWagon · Post by **WarWagon** » Fri Dec 16, 2011 5:47 pm

Can't say for sure, but they're likely all very similar. You have the lock ring that sets against the rear sight, and a similar ring that uses the provided wrench that is built in to the cover on the back of the aperture. I had to remove the lock ring that goes against the rear sight, and essentially grip the front most part of the aperture (closest to your eye) while unscrewing the back plate by gripping and turning that second lock ring that is part of the back plate. Once inside, it was pretty self explanatory.

I used a basic lens cleaning cloth that came with my Champion frames, but kim wipes or something similar would likely work. I did not use any cleaning fluids.