Magnetometer Questions

[pcolaboy]

Ok I'm a complete newbie when it comes to mags so I have some questions:

1. Do they only detect ferrous metals or can they also detect copper, gold, silver, etc?

2. How well would an average mag be able to detect under a foot or more of mud if its being towed in 20 feet of water?

3. What are the better "entry-level" mags that have locational ability on the market and where is the best place to buy them?

The reason why I'm asking is that I know a 89 year old shrimper that has given me some interesting sites to check out. The sidescan images of the area are inconclusive but the bottom in these areas is also extremely soft mud.

Thank in advance,

Pcola

 

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[diverlynn]

pcolaboy,
Mags will not detect anything but iron/ferrous material. The idea is that where there is iron there may be other goodies. Determining how to read the hits is the biggie. Modern iron will read (sometimes) larger gamma depending on how the object is laying and how deep. Find a hit, make a dive. A foot of mud is nothing, mags can pick up very deep. Just make sure if your close to the shore that you are not in anyones lease. Good luck
Diverlynn

 

[riobravo]

hi pcola,
there is a lot of answers to your questions in the geophysics forum, but to elaborate lightly the magnetometer detects deviations in the earths magnetic field primarily caused by ferrous objects, but with the sensitivity of some of todays equipment coupled with modern software and an experienced data analyzer you would be amazed at what you can detect.
JAS

 

[pcolaboy]

I certainly understand that where there's iron being detected, most likely there's a ship requiring some wet time. There's always a good excuse to get wet diving in my book.

The main ship of interest, if it is indeed the one I believe it to be, should show up on a mag like no ones business since there are historical indications it had portions fitted with iron ribbing. The shrimper I know said that when he was a kid he free dove on this site in an attempt to untangle his net and in the process retrieved a very large pieces of circular copper bands, presumably old barrel hoops. The visibility was poor but he said that it was very apparent to him that a very large ship was on the bottom sunken into the mud nearly to the gunwales and that it appeared to be somewhat intact.

When I sidescan the general area, I do see debris on the surface but when I switched to standard sonar I could definitely see a huge density change about 1-3 feet under the mud. I estimate the vessel or at least a substantial part of it to be in the range of 150' in length. If you look in my online gallery under the "PR" wreck you will see where I imaged the site last fall. We've only made one dive on it so far but the visibility was absolutely zero. However, I could 'feel' alot with my hands :-).

Thanks,

Pcola

 

[CaribbeanDiver]

I have a great mag that I will be selling for a few grand after I get done testing my new one next week if you are interested we could talk.

 

[CaribbeanDiver]

Here is the link to the mag for sale

http://www.endlesssummer.us/ebay1524/mag.htm

 

[Diver Down]

If you have questions about mags, the person to contact is Jim Whitaker. He has found a bunch of wrecks and NASA called him when the Challenger exploded.

He can be reached at [email protected]

Bill

 

[macblastr]

i am looking for a mag if anyone has one for sale...

you can email me at [email protected]

 

[riobravo]

If you have questions about mags, the person to contact is Jim Whitaker. He has found a bunch of wrecks and NASA called him when the Challenger exploded.

He can be reached at [email protected]

Bill

NASA called a lot of us when the challenger exploded.
but Jim is a great mag tech, he's the first one i refer people to when I'm too busy. which seems to be a lot these days