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PostPosted: Wed Jul 09, 2008 10:44 pm 
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Keithwms wrote:
Well, I am not saying that they were or weren't solarized or partly solarized, I just don't know. I am just saying that nanosecond exposures were possible with the rapatronics, so... it's possible that nonsolarized photos were achieved, and ~20 stops of range have been seen with POTA.

I see your comment about the initial gamma burst, but I am not sure offhand what the response of film will be to that. I do recall reading that a photographer who went to Chernobyl right after the accident had most of his film fogged pretty badly but he did manage to salvage a few snaps.

My guess is that for atomic bomb tests they put a lot of cameras behind a lot of lead and shot through some pretty thick glass from a long way away. The film itself can be behind the lead, only the lens needs to poke out, and the opening in the lead need only be as large as the aperture. Hell, the aperture itself could be made of lead 8) So, with a typical long lens, the opening would be a few millimeters, and thus the direct gamma burst would only hit a small central part of the film, while the image circle would be much larger than the aperture.... At least, that's what I'd try to do if I didn't want to have too much rad damage to my film.


I'd also use some nice leaded glass ... like Waterford.

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PostPosted: Thu Jul 10, 2008 5:14 am 
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Seefutlung wrote:
A 1/1000 ND filter ... would that be a 1/3" steel plate or maybe a 1/4" steel plate?

Gary


There are two kinds of filters in use: glas plates or mylar foils. In any case there is a heavy coating (preferably on both sides of the filter substrate), which really looks mirror-like, very, very reflective to visible and IR light. This layer is mostly made up of iron, but there are other metalls in the coating, which the producers don't publish. depending on the layer thickness you can control the density to tight tolerances. So the 1/1000 filter is for photographic use only. For visual use you would use the 1/10000 filter. The appaerance of the foil is very much like the cheap survival bag foil.

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René

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PostPosted: Thu Jul 10, 2008 8:41 pm 
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Silly me, and to think, I've been using #9 and #10 welding lenses all these years...


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PostPosted: Fri Jul 11, 2008 5:19 am 
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epatsellis wrote:
Silly me, and to think, I've been using #9 and #10 welding lenses all these years...
erie


Welding glass was quite common for solar watching. The problem is just, that nowadays these glasses are often imported from unknown sources and tests show, that they often don't block IR as well as they should. That can be quite dangerous for the eyes of an observer. Also, telescopes and tele lenses get bigger and bigger (more affordable) and welding glass is simply too small to cover the front of amateur telecopes today.

Another advantage of dedicated solar filters is, that the better ones show the sun disk in the orange colour you would expect, whereas welding glass mostly has a heavy green tint, which is not very pleasing, though you get used to it. In fact the green could serve as a contrast enhancement filter...

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PostPosted: Sat Jul 12, 2008 2:22 am 
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True, but I already have numerous good quality welding lenses already (not the cheap ones bought at wally world and such, but from reputable welding suppliers)


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