MawkHawk
sage
Reged: 08/23/09
Loc: SE Michigan, USA
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Re: Telescope Starts House Fire
[Re: hm insulators]
#5264378 - 06/10/12 08:21 AM
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Great. Now there will be a movement to ban telescopes...
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SteveG
Post Laureate
Reged: 09/27/06
Loc: Seattle, WA
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Re: Telescope Starts House Fire
[Re: MawkHawk]
#5264994 - 06/10/12 04:26 PM
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Great. Now there will be a movement to ban telescopes...
Not likely, but watch for the question "do you own a telescope" on your next home insurance application ;-)
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GeneT
Ely Kid
Reged: 11/07/08
Loc: South Texas
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Re: Telescope Starts House Fire
[Re: aznights]
#5265235 - 06/10/12 07:38 PM
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Although rare, this kind of accident can happen. Its just one more thing to think about when owning a telescope.
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Hermie
sage
Reged: 04/20/05
Loc: Cloudy HKG
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Re: Telescope Starts House Fire
[Re: GeneT]
#5265928 - 06/11/12 09:15 AM
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The butler did it!
With the finder. Another reason to use a telrad.
Hermie
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DeanS
Carpal Tunnel
Reged: 07/12/05
Loc: Central Kentucky
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Re: Telescope Starts House Fire
[Re: ZeroID]
#5266198 - 06/11/12 12:13 PM
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I had a concave shaving mirror in the back seat of my car many years ago. Sun came in and burned a long hole across the plastic roof lining where it reflected upwards ...just a chance in a million.
No fire thank goodness...
Had a similar incident in our bathroom. Wife left a make up mirror near the window, next day I noticed a 1" long burn on the window trim. That could have been ugly!
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Faith_J
Sketcher Extraordinaire
Reged: 11/17/04
Loc: South coast of England
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Re: Telescope Starts House Fire
[Re: DeanS]
#5266228 - 06/11/12 12:26 PM
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About 20 years ago, I burnt my hand when projecting the sun though the 6" scope I had then. I didn't think and inadvertently put my hand over the eyepiece, resulting in a bad burn. At least it wasn't my eye!
I have heard of people setting their clothes and even beards on fire before now. 
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jrbarnett
Eyepiece Hooligan
Reged: 02/28/06
Loc: Petaluma, CA
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Re: Telescope Starts House Fire
[Re: Faith_J]
#5266692 - 06/11/12 04:25 PM
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I get how this could happen with a Newtonian.
I'm less sure, however, how this happens with an SCT.
Regards,
Jim
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csrlice12
Post Laureate
Reged: 05/22/12
Loc: Denver, CO
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Re: Telescope Starts House Fire
[Re: MawkHawk]
#5266723 - 06/11/12 04:47 PM
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Was it a Bushnell, and has it previously been run over?
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KHHoran
member
Reged: 04/06/12
Loc: Rochester, NY
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Re: Telescope Starts House Fire
[Re: csrlice12]
#5266835 - 06/11/12 05:52 PM
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Okay, no real issue with leaving your scope set up in the house. But to not, at least, put the dust cover over the mirror/lens/corrector (whatever system you have) and finder scope?!? That's something I never forget to do. I also don't leave my eyepieces in either. There's a lot of dust that accumulates in a home, as I find out when I come home from a long business trip (my husband hasn't figured out Pledge yet  ), and I wouldn't leave the optics open to the environment like that. Fire hadn't even occurred to me, but as we've seen here, it's not unheard of.
I truly feel bad for the owners of the scope, but it seems as if this incident could have been avoided. Let this be a lesson.
-Kim
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SteveNH
professor emeritus
Reged: 07/10/11
Loc: Millbrae, CA
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Re: Telescope Starts House Fire
[Re: jrbarnett]
#5268848 - 06/12/12 10:56 PM
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I get how this could happen with a Newtonian.
I'm less sure, however, how this happens with an SCT.
Regards,
Jim
I absolutely agree, Jim. I don't think the fire investigators and news people realize that SCT's have a very short focus mirror. I still think the telescope did have something to do with starting the fire, just not directly by the mirror, if it started in the roof that far away - the optics don't make sense. It does seem possible though, that the secondary assembly would have been heated to melting temperatures with an f/2 mirror that large. I feel for his loss; it's too bad he didn't at least put a cover on the corrector, keeping it outdoors like that.
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aznights
member
Reged: 04/23/12
Loc: Glendale, AZ
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Re: Telescope Starts House Fire
[Re: SteveNH]
#5272587 - 06/15/12 10:34 AM
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What if it was actually a finder on the scope? Would that make more sense?
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SteveNH
professor emeritus
Reged: 07/10/11
Loc: Millbrae, CA
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Re: Telescope Starts House Fire
[Re: aznights]
#5273467 - 06/15/12 07:35 PM
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What if it was actually a finder on the scope? Would that make more sense?
Not to me. The most intense point of sunlight produced by a finder (outside its own tube) is located at the exit pupil, which is usually within a half inch behind the eye lens, and then it would diffuse quickly from there the farther away you get. And it would be doing all this in the opposite direction (behind the telescope), away from the roof that is claimed to be the kindling point, and toward the floor of the house instead.
Everyone's personal experiences above absolutely make sense - in every case, the burn points they report are always within a close proximity to the probable focal points of the concave mirrors involved. But in the case of this 14" SCT fire, the claimed ignition point is several times more distant than the 28" focal length of the mirror (practically at the front end of the tube). The mirror by itself cannot directly focus concentrated sunlight that far away onto the roof.
In the news photo, the front end of the 14" OTA aims right at the roof (5 to 10 feet away) at the point they claim the fire started. A 14" f/2 mirror will heat common metals to melting point in a very short time - maybe the secondary (which is missing in the photo) exploded, and sent red/white hot fragments flying into the roof!
In any case, it's just a big (and unfortunately real) nightmare.
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russell23
Post Laureate
Reged: 05/31/09
Loc: Upstate NY
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Re: Telescope Starts House Fire
[Re: hm insulators]
#5273972 - 06/16/12 05:44 AM
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After reading this thread I thought the light was passing through the tube completely. Then I watched the video. In the video the fire would need to be started by light reflected off the corrector plate.
Dave
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