Quote from: Trapezium Artist on May 23, 2013, 08:44:32 PM
Interesting: there are parallels to some work I did more than 20 years ago, while I was at the University of Arizona in Tucson.
I worked with Roger Angel in spring 1992 on the spin casting of the 6.5m diameter primary mirror for the MMT telescope on Mount Graham in southern Arizona. (MMT originally stood for Multiple Mirror Telescope, because it originally had 6 individual 1.8m diameter mirrors; the 6.5m single mirror replaced them all). Roger's spin casting technique involves melting chunks of glass in a giant rotating oven. Because the oven is rotating, the glass adopts a parabolic shape when it turns into a liquid: by holding that spin rate and then turning the oven off, you freeze the glass in a shape very close to the one you need to polish it to to make it useful in a telescope. Saves literally years of machining / polishing time.
(Actually, it's even cleverer than that, but I'll leave the interested to google for more info).
Anyway, during the casting of the MMT 6.5m mirror, I worked with a student called Dave Wittman to take pictures of the inside of the oven as the rotated, so we could make a time lapse movie of the glass melting and adopting its parabolic shape. This involved a CCD camera bolted to the outside of the oven staring through a glass window, taking a picture every 3 minutes for 33 hours or so.
Now, like you, we had the same problem: staring into a hold oven with melting glass over the base meant almost nothing was distinguishable: it was just a glowing mass of cherry-red and yellow. How was that solved? By firing a powerful UV flashgun every time the camera took a shot, and relying on the CCD being sensitive at short wavelengths. That provided all the contrast we needed, as can be seen in the resulting time lapse movies:
http://rc.arizona.edu/visualization-consulting/sample-visualization-projects (see the bottom of the page)
https://vimeo.com/channels/uofauitsweb/28960680
https://vimeo.com/channels/uofauitsweb/28960721
The pictures were b/w; we colourised them to make them look like the inside of an oven. And remember, this was 1992; be kind (I'm amazed that these are still on the web, to be honest
):
So, fast forwarding to the 21st century, one option for you could be to use a strong blue / UV spotlight on your metal work and use a corresponding filter on a stock video camera, admitting just that light. (If you use UV, of course, you need to be careful about your eyes too).
But I also suspect that this is a solved problem in similar areas, so some googling might be in order ...
Many many thanks Mr Artist, i do actually understand some of it but i think i will have to read it a couple more times before it sinks in! Most people would think it's an easy problem to solve but this is certainly the best advice i have received so far.
I knew nothing was beyond the knowledge of the Frostieverse.
Many thanks again
