I had some mud on a prism from carrying it on the ATV, and I rinsed it off, and now the prism is fogged up. I used it for a backsight yesterday, hoping that the warmer weather might clear it up.
It is still fogged up. I seem to remember that I had a prism fog up before, and it cleared up over time.
Thanks in advance,
Jimmy
A few thoughts, though none born of experience:
1. Pack it in rice.
2. Set it on a heating pad overnight.
3. Both!
Calcium Chloride, the world's best desiccant, and cheap too.
Works on total stations, data collectors, etc.
AC and heater on at the same time in the cab on the way to job site and on way back to office.
Is it a single round type prism? If so, there's probably a small crack in the rear of the housing close to the threads from it being dropped or hit at some point. Typically there is a plastic ring at the front of the housing that can be unscrewed with some effort then you can wipe the moisture from the rear of the prism and reinstall. A bit of Krazy Glue in the crack will reinforce it and a dab of silicon on the inside will help keep out water.
I used to be able to get replacement housings from my local dealer but haven't needed one in several years so I'm not sure if anyone still stocks just the housing.
Better the prism be foggy than the mind of the surveyor using it.
Steven is right. A compromise at the back of the canister will do it. Have you ever removed the glass, and looked at the back side?
N
A day on the dash of your truck on a Mississippi summer day will clear it up!
I had that happen to a prism I use when doing beach surveys. I was able to unscrew the black ring in the front and removed the glass from the casing. Once everything was dried and put back together I sealed the black ring with silicon, as this is where the water was leaking into the casing. Worked great, prism does not fog up anymore.
I second the silicone trick. And, the glass does not shift around inside the canister any more.
Way better.
N
All of mine that I've ever taken apart had a rubber o-ring that fit in a grove located an 1/8" to a 1/4" from the face of the prism. This keeps water from getting into the canister from the front. Every time a prism has fogged up on me it's been due to a cracked canister.
I don't think I have ever seen a Leica prism fog up. And I've been working in the great northwet for the last, this really hurts, 25 years. One reason my be the way their glass is mounted. The prism snaps into a holder that then fits into the yoke.