Lightning Strikes Observatory

Davoud wrote:


The owner of the observatory reports that he has talked to a couple of
others whose fiberglass-domed observatories have been struck by
lightning.


Implying what, Voudoo?


Davoud

--
usenet *at* davidillig dawt com

Davoud wrote:

Davoud:
The owner of the observatory reports that he has talked to a couple of
others whose fiberglass-domed observatories have been struck by
lightning.

William R. Mattil:
The veiled inference here is that fiberglass domes are more of a risk that
your Aluminum one ? lol

Not hardly.

John Nichols:
I took it more to mean that you should have a lightning rod and grounding.

What a jerk Mattil is! No wonder I don't see his posts directly :--)
What I wrote meant nothing at all

Voudoo religico magico astropathy? You could open a clinic and dispense
confusion!

; I quoted what I was told and made no
veiled references to anything whatsoever. Re-reading my post, I can
find no reference to my own observatory.

A lightning rod would be a great idea on such a structure; although the
dome in question was not the highest structure around, (nearby house
and trees) it is possible that the AP refractor on its pier was the
highest sizable bit of metal around and thus vulnerable.

This doesn't mean anything either: when I was in the communications
racket I noted that small fiberglass radomes on the roofs of buildings
were at least as vulnerable as nearby aluminum flagpoles and high metal
HF antenna masts.

Davoud

In article ,
Chris L Peterson wrote:

On Sat, 12 Aug 2006 22:25:47 -0500, William Hamblen
wrote:

I would think that the voltages present in lightning would exceed the
breakdown voltage of the dome, making the dome no protection at all
except to keep the rain out. Lightning could blow a hole in a light
weight metal dome.

Lightning does blow holes in thin metal- it is fairly common with
airplanes, for instance. But it isn't likely to pass through the dome
and arc into the interior of the observatory. The current travels on the
surface of conductors. That's why you are generally safe inside a car

.....except that one isn't quite as safe inside a car as commonly believed.
True, the metal in the car protects from a lighting strike, but if you're
unlucky, the gas tank of the car might explode. So if you really want
to be safe, empty the gas tank first, then ride out the thunderstorm inside
the car.

(or an airplane) when it is hit by lightning. Even the fiberglass dome
affords some protection, since the lightning might find the path of
least resistance via the surface. People are not usually hit by
lightning inside their houses, even if they have thin, non-conductive
roofs.
_________________________________________________

Chris L Peterson
Cloudbait Observatory
http://www.cloudbait.com
--
----------------------------------------------------------------
Paul Schlyter, Grev Turegatan 40, SE-114 38 Stockholm, SWEDEN
e-mail: pausch at stockholm dot bostream dot se
WWW: http://stjarnhimlen.se/

In article ,
Chris L Peterson wrote:

On Sat, 12 Aug 2006 19:13:02 -0400, Davoud wrote:

The owner of the observatory reports that he has talked to a couple of
others whose fiberglass-domed observatories have been struck by
lightning.

Interesting story. As someone whose own observatory was hit, I can
sympathize. I only lost all the electronics to the EMP; the optics were
fine. Amazing to hear of the mechanical damage. I can imagine that a
non-conductive dome would provide limited protection. It's a hard
problem to handle. A lightning rod would prevent the mechanical damage,
but probably wouldn't prevent the electronics from being seriously
damaged.

.....unless the electronics is built with vacuum tubes rather than
modern LSI chips. Vacuum tubes are much less vulnerable to EMP's. A
computer is of course infeasible to build with vacuum tubes, but a
variable frequency oscillator for the clock drive would be quite
feasible. But that might turn out to be more expensive than
replacing the modern electronics after the occasional lighting stike.

At some point you just have to accept that you can be unlucky,
and make sure you have insurance.

.....or you can be your own insurance company, and just save some
money for events like these. Doing so will be more cost effective in
the long run, since then you pay only your own bad luck. If you take
an insurance, you also pay part of the running costs and the profit
of the insurance company.

Paying for a lighning rod + proper lighning protection (which includes
thick wires buried in the ground and put around the building you want
to protect) is of course also well worth doing.

Not everything can be prevented.

_________________________________________________

Chris L Peterson
Cloudbait Observatory
http://www.cloudbait.com
--
----------------------------------------------------------------
Paul Schlyter, Grev Turegatan 40, SE-114 38 Stockholm, SWEDEN
e-mail: pausch at stockholm dot bostream dot se
WWW: http://stjarnhimlen.se/

A member of our club (http://www.astroimager.com) had a similar experience.
The lightning didn't strike his dome but it did hit the grounding lines and
ran into the dome, frying everything electronic in both the dome and his
control shed (AP mount, dome motorization, 3 computers, ST8, etc). He was
down for months while everything was repaired.

Ray Porter


"William Hamblen" wrote in message
...
On Sun, 13 Aug 2006 02:35:28 GMT, Chris L Peterson
wrote:

Interesting story. As someone whose own observatory was hit, I can
sympathize. I only lost all the electronics to the EMP; the optics were
fine. Amazing to hear of the mechanical damage. I can imagine that a
non-conductive dome would provide limited protection.

I would think that the voltages present in lightning would exceed the
breakdown voltage of the dome, making the dome no protection at all
except to keep the rain out. Lightning could blow a hole in a light
weight metal dome.

--
The night is just the shadow of the Earth.

On Sun, 13 Aug 2006 07:40:30 -0400, "Ray Porter"
wrote:

A member of our club (http://www.astroimager.com) had a similar experience.
The lightning didn't strike his dome but it did hit the grounding lines and
ran into the dome, frying everything electronic in both the dome and his
control shed (AP mount, dome motorization, 3 computers, ST8, etc). He was
down for months while everything was repaired.

In my case, the damage was apparently caused by induced currents in the
devices and cables. Nothing was connected to power at the time. I was
down for nearly two months, until I repaired or replaced my mount,
focuser, two cameras, port server, network switch, and miscellaneous
electronics. About the only thing that survived was a computer (although
the unplugged monitor was taken out).

The strike was about 10 meters from the observatory itself, and about 25
meters from my lab/warm room. I've got lots of electronics there, but
nothing was damaged.

_________________________________________________

Chris L Peterson
Cloudbait Observatory
http://www.cloudbait.com

On Sun, 13 Aug 2006 09:12:31 GMT, (Paul Schlyter) wrote:

....except that one isn't quite as safe inside a car as commonly believed.
True, the metal in the car protects from a lighting strike, but if you're
unlucky, the gas tank of the car might explode. So if you really want
to be safe, empty the gas tank first, then ride out the thunderstorm inside
the car.

Have you ever heard of a car exploding because of a lightning strike? It
must be extraordinarily rare! A gas tank, after all, is an awfully good
Faraday cage. I do know that an empty gas tank is generally more
dangerous than a full one, since it is the vapors that are explosive,
not the liquid.

In any case, from a risk analysis standpoint I'm sure the operation of
emptying the gas tank is more dangerous than sitting in the car during a
thunderstorm.

_________________________________________________

Chris L Peterson
Cloudbait Observatory
http://www.cloudbait.com

On Sun, 13 Aug 2006 09:12:31 GMT, (Paul Schlyter) wrote:

....unless the electronics is built with vacuum tubes rather than
modern LSI chips...

A bit of a problem for the cameras, too. Even if you built all the
control electronics from tubes, I don't think there is an alternative to
silicon for the sensors themselves. Maybe SBIG can introduce tube
cameras for lightning prone areas...


Paying for a lighning rod + proper lighning protection (which includes
thick wires buried in the ground and put around the building you want
to protect) is of course also well worth doing.

Yes, but electronics is still vulnerable to damage from the EMP. This is
the primary cause of damage to cell phone towers in the U.S. (structures
which are well protected with lightning rods). Some very sensitive
installations use a surrounding ring of lightning rods, but that's a lot
of trouble and expense for the typical amateur observatory.

_________________________________________________

Chris L Peterson
Cloudbait Observatory
http://www.cloudbait.com

Davoud wrote:
Davoud:
The owner of the observatory reports that he has talked to a couple of
others whose fiberglass-domed observatories have been struck by
lightning.

William R. Mattil:
The veiled inference here is that fiberglass domes are more of a risk that
your Aluminum one ? lol

Not hardly.

John Nichols:
I took it more to mean that you should have a lightning rod and grounding.

snip

A lightning rod would be a great idea on such a structure; although the
dome in question was not the highest structure around, (nearby house
and trees) it is possible that the AP refractor on its pier was the
highest sizable bit of metal around and thus vulnerable.

This doesn't mean anything either: when I was in the communications
racket I noted that small fiberglass radomes on the roofs of buildings
were at least as vulnerable as nearby aluminum flagpoles and high metal
HF antenna masts.

Davoud

How about a thin coat of carbon fibre/resin (plus a good earth) ?
reckon it might help act as a Faraday cage ?
Think I'll review my insurance policy...
jc

On 13 Aug 2006 07:46:05 -0700, "John Carruthers"
wrote:

How about a thin coat of carbon fibre/resin (plus a good earth) ?
reckon it might help act as a Faraday cage ?

The fiberglass dome is probably more conductive than you think. Odds are
that it has enough contaminants on the outside that lightning will
travel on the surface anyway (no guarantee, of course, as this story
demonstrates). However, even a perfect Faraday cage won't protect any
electronics inside, since it can't prevent damaging currents being
induced by the large magnetic field surrounding a lightning bolt.
Grounding is no help there, either.

Think I'll review my insurance policy...

Good idea.

_________________________________________________

Chris L Peterson
Cloudbait Observatory
http://www.cloudbait.com