[AMRadio] Somewhat Off topic - lightning protection


brian at arksky.org brian at arksky.org
Tue Jul 13 12:29:00 EDT 2004


This is somewhat off-topic, however the issue of lightning protection is important, and knowing how knowledgeable our
members are, I thought someone might have a solution to the following problem..

My brother has a very expensive telescope in an observatory located on Petit Jean Mtn. in Arkansas.  His telescope has a
computerized tracking and "GoTo" system built into the base of the mount which is mounted to a steel pier.  The steel
pier is bolted to a 14 ton concrete substructure that is about 5 feet in the ground under the floor.  The concrete
section has lots of rebar and iron meshing inside of it.

Lightning has taken out his computer control in the base three times in less than a year.  The last two times, nothing
was plugged into the unit so the base was simply at ground potential.  It appears that because of the bedrock
characteristics of this mountain, he is getting hit from the ground itself.  I can't think of any other way.

Someone emailed him the message below this morning as a possible solution, however I would be more inclined to install a
tower or something a bit further to serve as a lightning rod.  Maybe even treat the ground around the tower with Copper
Sulfate to something similar to help give it a good ground.  The suggestion below about running a copper perimeter 10'
around his observatory seems like it might add to the problem.  10 feet does not sound like enough distance to be
absorbing a direct hit of lightning.  Since the base of the scope and the pier are both metal, there is really no way to
isolate the telescope computer away from this.  It is much too heavy to use nylon bolts and an insulating pad between
the pier and concrete.

Any ideas or suggestions?

Thanks & 73,
Brian / w5ami


----- Original Message ----- 
From: "P. Clay Sherrod" <drclay at arksky.org>
To: <brian at arksky.org>

> No way at all....in fact I am convinced now that the lightening is coming up through the
> ground.
> I talked to an electronics guy yesterday (he owns SoundCraft) that suggested I build a #3
> copper perimeter ground around the base of the observatory, about 10 feet away from the
> walls with grounding rods on two opposing corners.....he says the problem up here is that
> you cannot get a proper ground on this mountain because of the rock.
>




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