Comments on: Did a telescope start a house fire in Arizona?

By: Kate Ebneter

Kate Ebneter — Thu, 14 Jun 2012 22:43:49 +0000

I’m surprised that so many people are skeptical of this. When I was in graduate school, some fellow TAs and I were aligning the 12-14″ Schmidt-Cassegrain that the department had for student use to do some solar projection stuff for some students. After a moment of moving the telescope around we smelled something burning and realized we had accidentally set one of us (his jacket, to be specific) on fire! We put the objective filter on then until we had the alignment set up properly. We had not done any focusing of the eyepiece, obviously, since we were not looking through the telescope (needless to say). I have no doubt that this very well could have happened, although, of course, “could have” != “did”.

By: Ken Williams

Ken Williams — Wed, 13 Jun 2012 03:17:27 +0000

Someone had better post this video: http://www.youtube.com/watch?v=z0_nuvPKIi8

Shows the HUGE heat that focused sunlight can put out.

By: ND

ND — Sun, 10 Jun 2012 06:00:10 +0000

Definitely Mythbusters material.

By: TeeDawg

TeeDawg — Sat, 09 Jun 2012 19:45:51 +0000

I had a mobile rv repair business for a couple of decades and used a Chevy Astro van to haul my tools around.

I kept the toolbox at the rear doors of the van. These doors were open as I returned to the van to grab more tools I noticed a wisp of smoke rising from an open toolbox drawer.

Sunlight reflecting off the concave inside glass found a focal point on the rubber handle of a screw driver, and as I picked it up to show the customer standing beside me, the rubber mat in the bottom of the drawer started to smolder almost right away.

I wonder how many of these vans were used for deliveries and how many cardboard boxes have been set alight!

By: Mark T-Williams

Mark T-Williams — Sat, 09 Jun 2012 14:50:22 +0000

A similar thing happened to my family when I was a little kid; about thirty years ago, my mother saved up for an 8″ Meade scope. Unfortunately, she didn’t have the chance to use it much. It was set up next to the living room window and only a couple weeks after purchase obligingly set the livingroom on fire. Luckily, noone was hurt, and the damage only took a couple weeks to repair. Amazingly, the telescope did survive and does still work — the main tube, one of the legs, and the houding for the eyepiece optics had to be replaced. It’s become kind of a family artifact, really.

By: John K

John K — Fri, 08 Jun 2012 18:44:28 +0000

Funny story to add here…I had rigged up my solar filter on one of my 7×35 binocular eyepieces. I put electrical tape over the other eyepiece so I wouldn’t look in by accident. Fortunately, I put the filter on the left eyepiece and looked into it with my right eye, leaving the right eyepiece (covered with tape) pointing over my shoulder. Watched the transit for only a few seconds and pulled back to look at the bonics…there was a smoldering hole in the tape over the right eyepiece. Good thing I didn’t stick my other eye there! I added a lot more tape and stern warnings (plus supervision) when I let other people use my rig. What I should’ve done was put a cover on the lens instead of trying to stop the light after it was already magnified and focused – d’oh!

By: W.C.

W.C. — Fri, 08 Jun 2012 18:40:41 +0000

I have installed a sprinkler system on my Meade ETX-125 and wear fire-protective gear at all times. Just in case, I have an ABC fire extiguisher affixed to my tripod. No ‘scope is g0ing to burn down my house.

By: Matt B.

Matt B. — Fri, 08 Jun 2012 18:12:06 +0000

@55 Brian Too: When did I say anything about mathematical certainty?

Also, that should not be used as a rule of thumb. Where the fire is most intense is usually the place with the best ventilation. Using the belief that the most intense fire is the place where it started is like using a rule of thumb that most rivers flow south. It may be true in a particular case, but you can’t reasonably depend on it–nowhere near 95%.

By: Jon Hanford

Jon Hanford — Fri, 08 Jun 2012 17:41:32 +0000

#48 Joe G asks “I wonder how common it is for people to build purpose-built solar telescopes?”

Homebuilt solar telescopes are actually quite popular with ATMs. Here’s a common design for a Newtonian solar telescope utilizing uncoated mirrors and a Herschel Wedge: http://www.considine.net/dgroski/wlnewt/

By: Cactospiza

Cactospiza — Fri, 08 Jun 2012 06:29:31 +0000

Watched a Galileoscope fitted with a Sunfunnel catch fire while watching the transit the other day at Lowell Observatory in Flagstaff AZ. The smoke escaped near the mounting lug, but it was unclear where the tube was actually burning inside. Demonstrates that not only could focussed rays ignite an external object, reflected rays (it was an SCT) could ignite an external object, but that internal heat (even with only internal mirrors) could have built up making the scope itself the initial ignition object.