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Main
Date: 12 Aug 2006 19:13:02
From: Davoud
Subject: Lightning Strikes Observatory
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About a month ago lightning struck an amateur observatory belonging to
a member of my astronomy club <http://www.howardastro.org >. The
observatory dome was made of fiberglass. I have not talked to the
owner, but I received this information from Company Seven, which has
first hand knowledge of the incident.
I have not seen the observatory, before or after the strike -- but I
have seen one of the damaged 'scopes, a Takahashi refractor of about 4"
aperture. The tube has two burn marks, one near the dew shield and one
on the tube near the focuser. The latter is roundish with a diameter of
2-3". The paint is gone and the underlying aluminum shows some signs of
slight surface melting, though the tube was not perforated. There is
also some blackening in the area. The damage appears to be typical of
that caused by electrical arcing. I did not have the opportunity to
look at the damaged area from inside the tube. The objective, which was
pristine, is spotted with an unknown material on its front surface. The
material gives the /appearance/ of being vaporized metal that condensed
in extremely thin spots. It is not considered economical to repair this
'scope.
It gets worse. A 6" Astrophysics refractor and its Astrophysics 1200
mount (neither of which I have seen) were destroyed. The Astrophysics
tube is said to have been destroyed from melting and fusing. The optics
were also destroyed, with pitting and loss of coatings. The mount has
its gears welded together, and is also a total loss.
The owner of the observatory reports that he has talked to a couple of
others whose fiberglass-domed observatories have been struck by
lightning.
Davoud
--
usenet *at* davidillig dawt com
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Date: 13 Aug 2006 02:35:28
From: Chris L Peterson
Subject: Re: Lightning Strikes Observatory
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On Sat, 12 Aug 2006 19:13:02 -0400, Davoud <star@sky.net > 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. At some point you just have to accept that you can be unlucky,
and make sure you have insurance. Not everything can be prevented.
_________________________________________________
Chris L Peterson
Cloudbait Observatory
http://www.cloudbait.com
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Date: 12 Aug 2006 22:25:47
From: William Hamblen
Subject: Re: Lightning Strikes Observatory
|
On Sun, 13 Aug 2006 02:35:28 GMT, Chris L Peterson
<clp@alumni.caltech.edu > 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.
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Date: 13 Aug 2006 03:44:18
From: Chris L Peterson
Subject: Re: Lightning Strikes Observatory
|
On Sat, 12 Aug 2006 22:25:47 -0500, William Hamblen
<wrhamblen@comcast.net > 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
(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
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Date: 13 Aug 2006 09:12:31
From: Paul Schlyter
Subject: Re: Lightning Strikes Observatory
|
In article <3o7td256dgm02h2ji96q3dd9g6mtbicbh2@4ax.com >,
Chris L Peterson <clp@alumni.caltech.edu > wrote:
> On Sat, 12 Aug 2006 22:25:47 -0500, William Hamblen
> <wrhamblen@comcast.net> 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/
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Date: 13 Aug 2006 13:50:58
From: Chris L Peterson
Subject: Re: Lightning Strikes Observatory
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On Sun, 13 Aug 2006 09:12:31 GMT, pausch@saaf.se (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
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Date: 14 Aug 2006 07:43:10
From: Paul Schlyter
Subject: Re: Lightning Strikes Observatory
|
In article <m8bud2hssqblf1o3if1vsb15dq3j1ocera@4ax.com >,
Chris L Peterson <clp@alumni.caltech.edu > wrote:
> On Sun, 13 Aug 2006 09:12:31 GMT, pausch@saaf.se (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?
I read a note about it in the paper here - it happened somewhere in Europe
this summer. Before that, I had considered the inside of a car as "totally
safe" during thunderstorms.
> It must be extraordinarily rare!
I fully agree about that. Otoh lighing stiking a car is quite rare too,
I almost never hear about that either. Lighting usually strikes much taller
items than a car.
> 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.
It's probably not the explosion that's dangerous, but the fire after the
explosion. And the gas tank is rarely completely empty or completely
full, it's usually partially full. So then there's vapors which might cause
an explosion, and then there's liquid gas which can catch fire afterwards.
> 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.
If done during the thunderstorm, yes. But if you have an old discarded
car near your house, you might as well keep it as a safe place during
thunderstorms - that car probably has an empty tank since long ago.
--
----------------------------------------------------------------
Paul Schlyter, Grev Turegatan 40, SE-114 38 Stockholm, SWEDEN
e-mail: pausch at stockholm dot bostream dot se
WWW: http://stjarnhimlen.se/
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Date: 13 Aug 2006 07:40:30
From: Ray Porter
Subject: Re: Lightning Strikes Observatory
|
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" <wrhamblen@comcast.net > wrote in message
news:756td213ut36rt8ghd8gvs2mshdr3c6c8a@4ax.com...
> On Sun, 13 Aug 2006 02:35:28 GMT, Chris L Peterson
> <clp@alumni.caltech.edu> 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.
|
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Date: 13 Aug 2006 13:45:49
From: Chris L Peterson
Subject: Re: Lightning Strikes Observatory
|
On Sun, 13 Aug 2006 07:40:30 -0400, "Ray Porter"
<ray_porter@alumni.unc.edu > 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
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Date: 13 Aug 2006 14:00:58
From: Davoud
Subject: Re: Lightning Strikes Observatory
|
Ray Porter:
> >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.
Chris L Peterson:
> 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).
These and other anecdotal reports serve to remind me of what I have
long known: ultimately, there is no practical protection, because
lightning need not strike a facility in order to damage it severely.
What it amounts to for my little zerbat'ry is that when I'm going to be
away for any length of time I remove such electronics as I can remove
easily: the Gemini control unit, the laptop, and the AirPort Express,
e.g. The BK Precision 18VDC power supply is on its own...
My neighbour tells me his boss lost a tv and vcr, a microwave oven, a
central AC relay box, and other electronics recently -- without a
strike. We lost a TV and a cable modem to this summer's severe
electrical storms -- the cable to our house consists of a 200-ft-long
"lightning antenna" buried deep under about 1-1/2" of soil. Again,
there was no evidence of a nearby strike.
Davoud
--
usenet *at* davidillig dawt com
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Date: 13 Aug 2006 11:15:44
From: Dan Mckenna
Subject: Re: Lightning Strikes Observatory
|
Davoud wrote:
> Ray Porter:
>
>>>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.
>
>
> Chris L Peterson:
>
>>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).
>
>
> These and other anecdotal reports serve to remind me of what I have
> long known: ultimately, there is no practical protection, because
> lightning need not strike a facility in order to damage it severely.
>
> What it amounts to for my little zerbat'ry is that when I'm going to be
> away for any length of time I remove such electronics as I can remove
> easily: the Gemini control unit, the laptop, and the AirPort Express,
> e.g. The BK Precision 18VDC power supply is on its own...
>
> My neighbour tells me his boss lost a tv and vcr, a microwave oven, a
> central AC relay box, and other electronics recently -- without a
> strike. We lost a TV and a cable modem to this summer's severe
> electrical storms -- the cable to our house consists of a 200-ft-long
> "lightning antenna" buried deep under about 1-1/2" of soil. Again,
> there was no evidence of a nearby strike.
>
> Davoud
>
The #1 recommendation of our lightning consultant was to upgrade the
building entrance lightning protection system as our damage will most
probably come from a tree strike going into the under ground utility
tunnel where the power lines run.
This is what seemed to happen last week at our site, no damage to our
scope but destroyed an expensive transfer switch.
d.
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Date: 13 Aug 2006 09:12:31
From: Paul Schlyter
Subject: Re: Lightning Strikes Observatory
|
In article <3n3td2p0jc7e4luovf9u7ip7osuq145otc@4ax.com >,
Chris L Peterson <clp@alumni.caltech.edu > wrote:
> On Sat, 12 Aug 2006 19:13:02 -0400, Davoud <star@sky.net> 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/
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Date: 13 Aug 2006 13:57:20
From: Chris L Peterson
Subject: Re: Lightning Strikes Observatory
|
On Sun, 13 Aug 2006 09:12:31 GMT, pausch@saaf.se (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
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Date: 13 Aug 2006 12:57:28
From: jtaylor
Subject: Re: Lightning Strikes Observatory
|
"Chris L Peterson" <clp@alumni.caltech.edu > wrote in message
news:2jbud25e6rsbblesgsl7ssrski6a8evd1a@4ax.com...
> 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...
Mechanically scanning photo-multiplier tubes?
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Date: 13 Aug 2006 16:46:03
From: Chris L Peterson
Subject: Re: Lightning Strikes Observatory
|
On Sun, 13 Aug 2006 12:57:28 -0300, "jtaylor"
<jtaylor@deletethis.hfx.andara.com > wrote:
>Mechanically scanning photo-multiplier tubes?
Ouch... talk about low QE. It would take days of integration time to get
a reasonable exposure with most objects.
_________________________________________________
Chris L Peterson
Cloudbait Observatory
http://www.cloudbait.com
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Date: 13 Aug 2006 09:11:37
From: Dan Mckenna
Subject: Re: Lightning Strikes Observatory
|
jtaylor wrote:
> "Chris L Peterson" <clp@alumni.caltech.edu> wrote in message
> news:2jbud25e6rsbblesgsl7ssrski6a8evd1a@4ax.com...
>
>
>>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...
>
>
> Mechanically scanning photo-multiplier tubes?
>
>
Film
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Date: 13 Aug 2006 16:44:28
From: Chris L Peterson
Subject: Re: Lightning Strikes Observatory
|
On Sun, 13 Aug 2006 09:11:37 -0700, Dan Mckenna
<dmckenna@as.arizona.edu > wrote:
>Film
Sorry, I should have said "good" alternatives to silicon <g >.
_________________________________________________
Chris L Peterson
Cloudbait Observatory
http://www.cloudbait.com
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Date: 14 Aug 2006 07:43:10
From: Paul Schlyter
Subject: Re: Lightning Strikes Observatory
|
In article <2jbud25e6rsbblesgsl7ssrski6a8evd1a@4ax.com >,
Chris L Peterson <clp@alumni.caltech.edu > wrote:
> On Sun, 13 Aug 2006 09:12:31 GMT, pausch@saaf.se (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...
One could resort to the good ol' way, using "chemical" rather than
electronic cameras.
But frankly, I see no need for keeping the electronic sensor out at
the telescope at all times. You need it there only when observing -
and you certainly don't observe during a thunderstorm. At other
times, electronic sensors as well as other kinds of loose electronics
(laptops/etc) can be kept in a safer place. Perhaps locked inside a
small metal cabinet, if you want good protection against the EMP.
>> 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.
MODERN electronics is.... :-)
> 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.
Cell phone towers must be operational at all times, also during
thunderstorms. An amateur observatory need not be operational during
a thunderstorm, so one can then (and not only during thunderstorms,
but at all times when one does not observe - as a precaution) remove
as much electronics as possible from there, and put it in a safer place.
--
----------------------------------------------------------------
Paul Schlyter, Grev Turegatan 40, SE-114 38 Stockholm, SWEDEN
e-mail: pausch at stockholm dot bostream dot se
WWW: http://stjarnhimlen.se/
|
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Date: 14 Aug 2006 14:25:53
From: Chris L Peterson
Subject: Re: Lightning Strikes Observatory
|
On Mon, 14 Aug 2006 07:43:10 GMT, pausch@saaf.se (Paul Schlyter) wrote:
>But frankly, I see no need for keeping the electronic sensor out at
>the telescope at all times. You need it there only when observing -
>and you certainly don't observe during a thunderstorm. At other
>times, electronic sensors as well as other kinds of loose electronics
>(laptops/etc) can be kept in a safer place. Perhaps locked inside a
>small metal cabinet, if you want good protection against the EMP.
Perhaps in some cases, but not all. It would be impractical for me to
regularly remove equipment from my observatory. The mount is fixed, much
of the electronics is mounted in a cabinet with permanently routed
wiring, and removing the camera would require spending time every
session collecting new calibration frames. The computer is a desktop
(although it isn't used normally for operating the equipment).
The purpose of the observatory is to have a setup ready to use on a
moment's notice. Having to go back to setting things up to image means I
just wouldn't do it often.
_________________________________________________
Chris L Peterson
Cloudbait Observatory
http://www.cloudbait.com
|
| |
Date: 13 Aug 2006 02:02:30
From: MT
Subject: Re: Lightning Strikes Observatory
|
"Davoud" <star@sky.net > wrote in message
news:120820061913022971%star@sky.net...
> About a month ago lightning struck an amateur observatory belonging to
> a member of my astronomy club <http://www.howardastro.org>. The
> observatory dome was made of fiberglass. I have not talked to the
> owner, but I received this information from Company Seven, which has
> first hand knowledge of the incident.
>
Didn't the idiot insure scopes like that?
|
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Date: 12 Aug 2006 22:12:56
From: Davoud
Subject: Re: Lightning Strikes Observatory
|
Davoud:
> > About a month ago lightning struck an amateur observatory belonging to
> > a member of my astronomy club <http://www.howardastro.org>. The
> > observatory dome was made of fiberglass. I have not talked to the
> > owner, but I received this information from Company Seven, which has
> > first hand knowledge of the incident.
MT, reading something I did not write, replied:
> Didn't the idiot insure scopes like that?
The man is much closer to a genius than he is to an idiot. But
alongside you a common garden slug looks like a genius. Of course he
has insurance.
Davoud
--
usenet *at* davidillig dawt com
|
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Date: 13 Aug 2006 15:31:39
From: MT
Subject: Re: Lightning Strikes Observatory
|
"Davoud" <star@sky.net > wrote in message
news:120820062212560569%star@sky.net...
> Davoud:
>> > About a month ago lightning struck an amateur observatory belonging to
>> > a member of my astronomy club <http://www.howardastro.org>. The
>> > observatory dome was made of fiberglass. I have not talked to the
>> > owner, but I received this information from Company Seven, which has
>> > first hand knowledge of the incident.
>
> MT, reading something I did not write, replied:
>> Didn't the idiot insure scopes like that?
>
> The man is much closer to a genius than he is to an idiot. But
> alongside you a common garden slug looks like a genius. Of course he
> has insurance.
>
> Davoud
Then what is the problem?
|
| |
Date: 13 Aug 2006 00:08:05
From: William R. Mattil
Subject: Re: Lightning Strikes Observatory
|
Davoud wrote:
[snip]
> The owner of the observatory reports that he has talked to a couple of
> others whose fiberglass-domed observatories have been struck by
> lightning.
The veiled inference here is that fiberglass domes are more of a risk
that your Aluminum one ? <lol >
Not hardly.
Bill
--
William R. Mattil : http://www.celestial-images.com
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| | |
Date: 13 Aug 2006 00:22:25
From: John Nichols
Subject: Re: Lightning Strikes Observatory
|
"William R. Mattil" <wrmattil@ix.netcom.com > wrote in message
news:F3uDg.399$q63.295@newssvr13.news.prodigy.com...
> Davoud wrote:
> [snip]
>
>> The owner of the observatory reports that he has talked to a couple of
>> others whose fiberglass-domed observatories have been struck by
>> lightning.
>
> The veiled inference here is that fiberglass domes are more of a risk that
> your Aluminum one ? <lol>
>
> Not hardly.
>
I took it more to mean that you should have a lightning rod and grounding.
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Date: 12 Aug 2006 21:27:45
From: Davoud
Subject: Re: Lightning Strikes Observatory
|
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; 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
|
| | | | |
Date: 12 Aug 2006 21:29:26
From: David G. Nagel
Subject: Re: Lightning Strikes Observatory
|
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; 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.
>
Lightning protection provided by surrounding structures and trees is
limited to about 1 1/2 times their height. Anything outside that
distance is fair game to mother nature. Anything inside that distance is
fair game to mother nature also. Don't expect anything to protect you
if mother wants you.
Dave N
> 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
|
| | | | | |
Date: 13 Aug 2006 11:04:37
From: Greg Campbell
Subject: Re: Lightning Strikes Observatory
|
David G. Nagel wrote:
> Davoud wrote:
> Lightning protection provided by surrounding structures and trees is
> limited to about 1 1/2 times their height. Anything outside that
> distance is fair game to mother nature. Anything inside that distance is
> fair game to mother nature also. Don't expect anything to protect you
> if mother wants you.
>
> Dave N
FWIW, I'd say the width of the 'cone of protection' is closer to 1/3 the
height of the tree, etc. Even then, as you say, there are absolutely
no guarantees. A descending stepped leader is largely blind to anything
much further away than 50~100 ft. Even when close to a potential
target, the ground must provide a positive streamer to connect to, and
those can/will come from anywhere.
Somewhere on line I've seen a picture of a lightning bolt hitting the
Sears tower - at a point halfway to the ground. As I recall, the bolt
parallels the building, maybe 100~200 feet away, for an impressive
distance before veering in for the hit, just below the building's bottom
'step.'
Running a few grounded cables over the observatory dome should keep the
main charge away from your equipment. Of course any electronics in the
area will still be fair game.
-Greg
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| | | | |
Date: 13 Aug 2006 03:29:58
From: j w
Subject: Re: Lightning Strikes Observatory
|
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
|
| |
Date: 13 Aug 2006 09:10:51
From: Dan Mckenna
Subject: Re: Lightning Bites Observatory
|
Davoud wrote:
> About a month ago lightning struck an amateur observatory belonging to
> a member of my astronomy club <http://www.howardastro.org>. The
> observatory dome was made of fiberglass. I have not talked to the
> owner, but I received this information from Company Seven, which has
> first hand knowledge of the incident.
>
This is not cheap, easy or 100%
In protecting a small observatory it seems to me the best way is with
a elevated catanary(sp?) like used on some oil storage yards and a solar
telescope on Kitt Peak. For example three metal flag poles with a heavy
cable forming an elevated triangle. The poles are connected by a loop
and then radials attached, just like you would build a high power
transmitting antenna. Some blockage of the sky will occur and it can
form an ice fall hazard in some climates.
One of the problems is that small observatories are small.
In trying to protect a low conductivity structure one installs lightning
rods.
For a dome several rods are used and a path to the observatories
lightning ground is provided. Usually more than one attachment is used
to the observatory lightning ground.
Lightning is a complex process that can have current rise times in the
sub microsecond and in part is modeled as RF
Instead of a bolt from the blue, think of a very large electric field
(DC) from an elevated dipole breaking down i.e. turning conductive in an
series of ion avalanches. If you are ground for this event during the
return path you are the winner of 10's to 100s of thousand maybe up to
250,000 or so amps of current.
This can cause near by regions not involved with the direct discharge to
have "secondary" attachments occur near the main event.
For DC a 100,000 amp peak current needs a resistance less than 0.001 ohm
so that the down lead voltage drop is 100 volts.
As the RF part of the current wants low inductance, even the bend radius
of the down conductors is important. Thus a low resistance path is not
the total answer.
The installation of rods on a small dome may have inductances and bends
that will cause a break down to the nearest conductor....Da scope.
As the dome is a FG dome, a poor conductor, secondary breakdown may form
in the dome area and the lack of magnetic shielding can lead to
induced failures in the nearby electrical/electronics.
Thus an elevated ground puts distance and gets the most intense fields
some what away.
Still the FG dome will not shield even though it is not directly attached.
I am rebuilding our observatory power system to have power contactors
that disconnect outside power with a push of a button or bit. right now
I go around unplugging things and turning off breakers.
Still, once in a while something goes BOOM during the monsoon season and
we try to find out why.
d.
|
| |
Date: 13 Aug 2006 07:46:05
From: John Carruthers
Subject: Re: Lightning Strikes Observatory
|
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
|
| | |
Date: 13 Aug 2006 14:55:30
From: Chris L Peterson
Subject: Re: Lightning Strikes Observatory
|
On 13 Aug 2006 07:46:05 -0700, "John Carruthers"
<joncarruthers@hotmail.com > 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
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| | | |
Date: 13 Aug 2006 16:58:41
From: Sam Wormley
Subject: Re: Lightning Strikes Observatory
|
Chris L Peterson wrote:
> 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.
Faraday Cage
http://scienceworld.wolfram.com/physics/FaradayCage.html
A conducting cage used to shield electronic equipment. Amazingly,
the law of electrostatics conspire so that electric fields outside
are completely canceled out in the interior, as well as vice versa.
|
| | | | |
Date: 13 Aug 2006 17:37:47
From: Chris L Peterson
Subject: Re: Lightning Strikes Observatory
|
On Sun, 13 Aug 2006 16:58:41 GMT, Sam Wormley <swormley1@mchsi.com >
wrote:
> Faraday Cage
> http://scienceworld.wolfram.com/physics/FaradayCage.html
>
> A conducting cage used to shield electronic equipment. Amazingly,
> the law of electrostatics conspire so that electric fields outside
> are completely canceled out in the interior, as well as vice versa.
No help for the magnetic field, though.
_________________________________________________
Chris L Peterson
Cloudbait Observatory
http://www.cloudbait.com
|
| | | | | |
Date: 13 Aug 2006 19:18:59
From: Sam Wormley
Subject: Re: Lightning Strikes Observatory
|
Chris L Peterson wrote:
> On Sun, 13 Aug 2006 16:58:41 GMT, Sam Wormley <swormley1@mchsi.com>
> wrote:
>
>> Faraday Cage
>> http://scienceworld.wolfram.com/physics/FaradayCage.html
>>
>> A conducting cage used to shield electronic equipment. Amazingly,
>> the law of electrostatics conspire so that electric fields outside
>> are completely canceled out in the interior, as well as vice versa.
>
> No help for the magnetic field, though.
>
> _________________________________________________
>
> Chris L Peterson
> Cloudbait Observatory
> http://www.cloudbait.com
If a magnetic field can generate currents in electronics, it will
do so in a true Faraday cage. Mu-metals are high magnetic permeability
alloys that are used to shield magnetic fields in applications where
a true Faraday cage is not practical.
|
| | | | | | |
Date: 13 Aug 2006 19:49:47
From: Chris L Peterson
Subject: Re: Lightning Strikes Observatory
|
On Sun, 13 Aug 2006 19:18:59 GMT, Sam Wormley <swormley1@mchsi.com >
wrote:
> If a magnetic field can generate currents in electronics, it will
> do so in a true Faraday cage. Mu-metals are high magnetic permeability
> alloys that are used to shield magnetic fields in applications where
> a true Faraday cage is not practical.
Even if you were to build a mu-metal enclosure (which would be
astronomically expensive), the material saturates at fairly low field
strengths. That is, the mu-metal magnetizes fairly easily, and once it
is magnetized it no longer shields. So a near-miss lightning strike is
still going to produce dangerous currents in electronics- especially
where you have long cabling.
_________________________________________________
Chris L Peterson
Cloudbait Observatory
http://www.cloudbait.com
|
| | | | | | | |
Date: 13 Aug 2006 14:20:58
From: Dan Mckenna
Subject: Re: Lightning Strikes Observatory
|
Chris L Peterson wrote:
> On Sun, 13 Aug 2006 19:18:59 GMT, Sam Wormley <swormley1@mchsi.com>
> wrote:
>
>
>> If a magnetic field can generate currents in electronics, it will
>> do so in a true Faraday cage. Mu-metals are high magnetic permeability
>> alloys that are used to shield magnetic fields in applications where
>> a true Faraday cage is not practical.
>
>
> Even if you were to build a mu-metal enclosure (which would be
> astronomically expensive), the material saturates at fairly low field
> strengths. That is, the mu-metal magnetizes fairly easily, and once it
> is magnetized it no longer shields. So a near-miss lightning strike is
> still going to produce dangerous currents in electronics- especially
> where you have long cabling.
>
> _________________________________________________
>
> Chris L Peterson
> Cloudbait Observatory
> http://www.cloudbait.com
yes indeed
In the PMT days we made photomultiplier shields using mu metals.
Very hard to work with and still have a good shield.
You must put the assembly in a soft iron tube to prevent saturation and
if you bend it to much then it needs to be heat treated.
A quick look at the ever growing EMP related pages on the web is now
starting to show EMP zip cable as well as multi layer foils and
conductive concrete.
911
d.
|
| | | | | | | |
Date: 13 Aug 2006 19:56:03
From: Sam Wormley
Subject: Re: Lightning Strikes Observatory
|
Chris L Peterson wrote:
> On Sun, 13 Aug 2006 19:18:59 GMT, Sam Wormley <swormley1@mchsi.com>
> wrote:
>
>> If a magnetic field can generate currents in electronics, it will
>> do so in a true Faraday cage. Mu-metals are high magnetic permeability
>> alloys that are used to shield magnetic fields in applications where
>> a true Faraday cage is not practical.
>
> Even if you were to build a mu-metal enclosure (which would be
> astronomically expensive), the material saturates at fairly low field
> strengths. That is, the mu-metal magnetizes fairly easily, and once it
> is magnetized it no longer shields. So a near-miss lightning strike is
> still going to produce dangerous currents in electronics- especially
> where you have long cabling.
>
> _________________________________________________
>
> Chris L Peterson
> Cloudbait Observatory
> http://www.cloudbait.com
And that is why true Faraday cages are not very practical as
the are vulnerable to damage among other things.
|
| | | | | |
Date: 13 Aug 2006 18:30:47
From: Sam Wormley
Subject: Re: Lightning Strikes Observatory
|
Chris L Peterson wrote:
> On Sun, 13 Aug 2006 16:58:41 GMT, Sam Wormley <swormley1@mchsi.com>
> wrote:
>
>> Faraday Cage
>> http://scienceworld.wolfram.com/physics/FaradayCage.html
>>
>> A conducting cage used to shield electronic equipment. Amazingly,
>> the law of electrostatics conspire so that electric fields outside
>> are completely canceled out in the interior, as well as vice versa.
>
> No help for the magnetic field, though.
>
> _________________________________________________
>
> Chris L Peterson
> Cloudbait Observatory
> http://www.cloudbait.com
I think all electromagnetic radiation. However, most structures are
not even close to Faraday cages at the wavelength associated with
lightning.
|
| | | | | | |
Date: 13 Aug 2006 14:42:41
From: Greg Neill
Subject: Re: Lightning Strikes Observatory
|
"Sam Wormley" <swormley1@mchsi.com > wrote in message news:rdKDg.89097$FQ1.65754@attbi_s71...
> Chris L Peterson wrote:
> > On Sun, 13 Aug 2006 16:58:41 GMT, Sam Wormley <swormley1@mchsi.com>
> > wrote:
> >
> >> Faraday Cage
> >> http://scienceworld.wolfram.com/physics/FaradayCage.html
> >>
> >> A conducting cage used to shield electronic equipment. Amazingly,
> >> the law of electrostatics conspire so that electric fields outside
> >> are completely canceled out in the interior, as well as vice versa.
> >
> > No help for the magnetic field, though.
> >
> > _________________________________________________
> >
> > Chris L Peterson
> > Cloudbait Observatory
> > http://www.cloudbait.com
>
> I think all electromagnetic radiation. However, most structures are
> not even close to Faraday cages at the wavelength associated with
> lightning.
Suggested Experiment:
Wrap a magnet tightly in a ball of aluminum foil so
that it is in effect contained in a Faraday cage.
Will it still attract ferromagnetic materials
outside the foil?
|
| | | | | | | |
Date: 13 Aug 2006 12:19:21
From: Dan Mckenna
Subject: Re: Lightning Strikes Observatory
|
Greg Neill wrote:
> "Sam Wormley" <swormley1@mchsi.com> wrote in message news:rdKDg.89097$FQ1.65754@attbi_s71...
>
>>Chris L Peterson wrote:
>>
>>>On Sun, 13 Aug 2006 16:58:41 GMT, Sam Wormley <swormley1@mchsi.com>
>>>wrote:
>>>
>>>
>>>> Faraday Cage
>>>> http://scienceworld.wolfram.com/physics/FaradayCage.html
>>>>
>>>> A conducting cage used to shield electronic equipment. Amazingly,
>>>> the law of electrostatics conspire so that electric fields outside
>>>> are completely canceled out in the interior, as well as vice versa.
>>>
>>>No help for the magnetic field, though.
>>>
>>>_________________________________________________
>>>
>>>Chris L Peterson
>>>Cloudbait Observatory
>>>http://www.cloudbait.com
>>
>> I think all electromagnetic radiation. However, most structures are
>> not even close to Faraday cages at the wavelength associated with
>> lightning.
>
>
> Suggested Experiment:
>
> Wrap a magnet tightly in a ball of aluminum foil so
> that it is in effect contained in a Faraday cage.
> Will it still attract ferromagnetic materials
> outside the foil?
For a static DC field a Faraday cage works.
Conductive non ferromagnetic materials will transmit a static magnetic
field.
The moment you have microsecond rise time currents then you have eddy
currents, skin and other propagation effects that can change all that.
That's why you can play magnetic ring toss with a copper loop.
You are right wanting a high permeability material for shielding.
d.
|
| |
Date: 13 Aug 2006 03:27:17
From: j w
Subject: Re: 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
|
| |
Date: 14 Aug 2006 21:36:55
From: w_tom
Subject: Re: Lightning Strikes Observatory
|
Dan Mckenna wrote:
> For high resistivity soils I would think a radial ground would perform
> better than a rod. Radials from the iso-loop is best, would be my guess.
Radials (and I assume you mean counterpoise) suffers from being in
ground that sometimes freezes, gets dry, and does not create
equipotential beneath the building.
Earthing is performed for two reasons: conductivity and
equipotential. First lightning must have the most conductive path to
earth so that a higher voltage does not cause it to seek alternative
earthing paths. Second, the earth beneath that building must be
equipotential so that (again) there are no other better paths to
earthborne charges distant.
One simple way to drive a rod deeper. Electrode is in soil that is
always moist, does not freeze, causes greater surface area between
electrode and earth, causes better equipotential to farther reaches of
the building, and may even cut through and contact deeper, more
conductive geology. A second alternative is the halo (ring) ground or
Ufer ground that also creates even better equipotential, better
distributes conductivity, again is in always moist soil, and would
probably be a least expensive solution for most equipotential and
conductivity.
Counterpoise is usually limited to geologies that are too rocky and
where the radial lines are being laid in direct contact to conductive
(typically igneous) rock. It is a compromise because conductivity
decreases rapidly as soil freezes or 'clumps' due to drying.
Obviously, earthing is adapted for geological conditions. But
earthing should be planned for and installed before footings are even
poured. Best earthing. Least cost.
|
| |
Date: 14 Aug 2006 09:53:06
From: w_tom
Subject: Re: Lightning Strikes Observatory
|
Dan Mckenna wrote:
> The #1 recommendation of our lightning consultant was to upgrade the
> building entrance lightning protection system as our damage will most
> probably come from a tree strike going into the under ground utility
> tunnel where the power lines run.
>
> This is what seemed to happen last week at our site, no damage to our
> scope but destroyed an expensive transfer switch.
Major reason why some confuse a nearby strike (EMP) with what is
really a direct strike is GPR. That 'tree strike' creates GPR which
causes voltage potentials inside the building. Things considered
non-conductive such as tabletops, concrete, and linoleum tile even
contribute to making destructive electrical circuits.
GPR is why a four legged animal only standing near the tree sufferes
what is a direct lightning strike. Currents down tree and seeking
earthborne charges some miles distance will also travel up the cows
hind legs and down its fore legs. That is a direct strike so powerful
as to kill the cow. It demonstrates how nearby strikes, so often
confused with EMP, instead are direct strikes.
A best solution to GPR is a halo or ring ground so that earth beneath
the structure remains equipotential. This solution (or Ufer grounds)
should be standard solutions to all buildings before footings are even
poured. However we routinely do earthing as an afterthought - after
the foundation is pours. Therefore insufficient earthing causes damage
inside a building.
Anything that violates integrity of that ring (ie each wire inside
that tunnel) must connect to that ring where tunnel crosses the
protected circle. Damage occurs because of electrical currents. EMP
is made irrelevant by protection inside all electronics and by
protection installed from direct strikes. Newer electronics now
contain superior protection up to 2000 and 15000 volts per IEC1000-4-2.
Why does lightning strike a fiberglass dome? Lightning knows no
difference between miles of sky and that dome. Lightning seeks earth.
If better earthing is inside that dome, then lightning will find that
path destructively.
We don't stop, block, or absorb lightning. That dome does not stop
lightning. We present lightning a better path to earth. All
protection is about earthing. In this case, the Franklin solution is a
lightning rod. How effective is that rod? Well, how well earthed is
it? A lightning rod that makes a better connection to earth and
outside that halo (ring) earthing electrode means lightning will not
find a destructive path through fiberglass dome or electronics.
An observatory is well earthed, obviously, for stability. That
concrete can make the observatory a preferred path for lightning.
Demonstrates why a lightning rod connected only to a 4 foot earthing
electrode would not provide effective protection. Earthing electrode
must be superior. Consider up to a 30 foot earthing rod.
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