[RioRico]

I was reading Astronomy magazine a few weeks ago while waiting in the dentists office and there was a whole article about the glass in eyepieces cracking and sometimes blowing out due to heat buildup in telescopes aimed at the sun with the so called "safe" solar filters and the writer did just that. They heated up to dangerous conditions relatively fast. The mag was a couple of years old and I don't remember the exact issue to reference it. I would assume the same fate awaits cameras. The main theme of the article was that just because lots of people get away with this practice doesn't mean it's safe, despite the ad claims from the people who make and sell the filters.

Hmmm. As I mentioned, I shot the eclipse with my K20D mounting 900mm optics (300mm tele with 3x TC) and 950nm IR filter. Camera+optics were pointed at Sol for 1.5 hours, with LiveView on most of the time. I occasionally felt the lens and it didn't feel hot. I wonder what optics were involved in the Astronomy magazine article? Do long.lenses (*) vs teles vs mirrors make a difference? If mirrors, where were the filters placed: in front or in back? (Many big-objective mirrors have a small filter slot in the base.) I would expect a mirror with a rear-mounted filter to heat up considerably. More research is needed. Can we get a grant?
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(*) For those who don't know: A telephoto lens incorporates an optical feature called a telephoto group (the opposite of a retrofocus or wide-angle group) to make a lens appear optically longer than it is. Thanks to such, my little Enna Tele-Sandmar 100/4.5 is only 35mm long. A long.lens is just a tube with glass at one end and a camera at the other. Thus my Meyer Trioplan 100/2.8 is 80mm long, sitting atop the camera register distance of ~45mm.

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Last edited by RioRico; 05-27-2012 at 09:35 AM.

[reeftool]

Hmmm. As I mentioned, I shot the eclipse with my K20D mounting 900mm optics (300mm tele with 3x TC) and 950nm IR filter. Camera+optics were pointed at Sol for 1.5 hours, with LiveView on most of the time. I occasionally felt the lens and it didn't feel hot. I wonder what optics were involved in the Astronomy magazine article? Do long.lenses (*) vs teles vs mirrors make a difference? If mirrors, where were the filters placed: in front or in back? (Many big-objective mirrors have a small filter slot in the base.) I would expect a mirror with a rear-mounted filter to heat up considerably. More research is needed. Can we get a grant?
____________________________________________

(*) For those who don't know: A telephoto lens incorporates an optical feature called a telephoto group (the opposite of a retrofocus or wide-angle group) to make a lens appear optically longer than it is. Thanks to such, my little Enna Tele-Sandmar 100/4.5 is only 35mm long. A long.lens is just a tube with glass at one end and a camera at the other. Thus my Meyer Trioplan 100/2.8 is 80mm long, sitting atop the camera register distance of ~45mm.

I'm not up on the terminology and the different types of telescopes so I'm at a bit of a loss as to what type. Perhaps I should visit the dentist and hope it's still there. The article itself was geared to advanced sky watchers so I'm assuming he was refering to high end telescopes. His main concern was eye damage and not from light damage. The filters used were doing their job in that respect. There were instances mentioned that when the eyepiece glass cracked, very tiny shards of glass can hit the eye. It happened to one of his. He wasn't looking through it when it happened.

[pixelsaurus]

The main theme of the article was that just because lots of people get away with this practice doesn't mean it's safe, despite the ad claims from the people who make and sell the filters.

All the more reason to buy solar filters from reputable retailers. Some examples are:

Orion Full-Aperture Glass Telescope Solar Filters | Orion Telescopes

Astro-Physics Inc.

Thousand Oaks White Light Glass Solar Filters - OPT Telescopes

Baader Products For Solar Observing

[Jrink]

I mised that Venus transit, shame on me.. next time :-)

[DeadJohn]

@Jrink, the transit is on Tues June 5. You didn't miss it.