by NoelC » Fri May 16, 2008 7:01 pm
When I was a teenager (too many decades ago) I had a small 2-1/2" refractor telescope that came with a "Sun Filter" that screwed onto the eyepiece. I used it to look at the sun sometimes. I never thought about it much; I was doing exactly what the telescope book said to do.
One day - thankfully at a time when I was not looking through the telescope - the filter broke into two pieces, falling out of its little screw-on mount and into the diagonal. It was because the concentration of sunlight had heated the filter glass so much that the thermal stress was simply too much for it.
I had been looking at the sun just a moment prior.
What impressed me most at the time, and stuck with me since, was that if I had been looking at the sun at that very moment, quite likely the concentrated sunlight would have literally burned out my eye, even before I could blink. I would have lost my sight in a most agonizing way. I have a crystalline memory of the brilliant, hot light coming up out of the eyepiece just after the filter broke, accompanied by just a wisp of smoke, before I moved the telescope to point away from the sun.
Never, ever, NEVER EVER point a telescope at the sun without the light being properly filtered at the objective end.
-Noel
When I was a teenager (too many decades ago) I had a small 2-1/2" refractor telescope that came with a "Sun Filter" that screwed onto the eyepiece. I used it to look at the sun sometimes. I never thought about it much; I was doing exactly what the telescope book said to do.
One day - thankfully at a time when I was not looking through the telescope - the filter broke into two pieces, falling out of its little screw-on mount and into the diagonal. It was because the concentration of sunlight had heated the filter glass so much that the thermal stress was simply too much for it.
I had been looking at the sun just a moment prior.
What impressed me most at the time, and stuck with me since, was that if I had been looking at the sun at that very moment, quite likely the concentrated sunlight would have literally burned out my eye, even before I could blink. I would have lost my sight in a most agonizing way. I have a crystalline memory of the brilliant, hot light coming up out of the eyepiece just after the filter broke, accompanied by just a wisp of smoke, before I moved the telescope to point away from the sun.
Never, ever, NEVER EVER point a telescope at the sun without the light being properly filtered at the objective end.
-Noel