Andy Perrin Posted June 25, 2020 Share Posted June 25, 2020 Thanks, Jonathan, that’s pretty much what I was expecting. There is no 250nm sunshine. Ergo any signal must be out of band. Link to comment
JMC Posted June 25, 2020 Share Posted June 25, 2020 No problem folks. I have no doubt that with a 256nm lamp, the story will be very different. I did have one on order - a tube to fit one of my BlakRay lamps - but it never arrived, and I eventually got my money back. If I ever end up getting one I'll give it a go. Link to comment
dabateman Posted June 25, 2020 Share Posted June 25, 2020 Excellent!Thank you Jonathon. Now I don't have to repeat my test. Also its been raining today. So would have to wait any way. However, one thing I do need to test is with my portable 254nm light outside. I wonder what the difference will look like. Link to comment
Bill De Jager Posted June 26, 2020 Share Posted June 26, 2020 Sure, but I'm sure if you were out in the open it would fade by the time you were tens of meters away, like in fog. I mean you can SEE in fog usually in a steamy bathroom for example. But outdoors things go white. I imagine things would go black in UVC. Here is the absorption coefficient of all the major atmospheric gases: Sigh... I forgot that the original question referred to sunlight. Yes, the ozone layer filters out just about all solar radiation under 300nm. However, my understanding is that O2 doesn't come into play until ~200nm. The graph you provided lumps the two gases together which is not helpful. I don't see any other gas that would cause a fog-like appearance at 250 nm. Sunlight should be insignificant to none, while strong sources on the earth's surface should provide good illumination at close distances with attenuation primarily due to distance rather than absorption or scattering. Link to comment
Andy Perrin Posted June 26, 2020 Share Posted June 26, 2020 Yeah, I took the graph I put on here before as meaning that O3 and O2 had similar spectra, but it seems they meant the MIXTURE of the two gases had that spectrum. As you say, unhelpful. I did manage to dig this one up, and yes, in fact O2 doesn't absorb until under 200nm:cite: http://www.cnofs.org...985/Chptr22.pdf So no fog-like effect, but things will be dark outdoors because there is no sunshine at all, and very few man-made sources of UVC. Link to comment
Stefano Posted June 26, 2020 Share Posted June 26, 2020 What a strange place the world is at these wavelengths! Basically a UVC lamp is a little torch shining light in a obscure world. Corona discharges may be the only (weak) light source in this band. Link to comment
Bill De Jager Posted June 27, 2020 Share Posted June 27, 2020 I would also expect UV-C from lightning, given that the associated plasma runs around 50000 K. Link to comment
Avalon Posted August 3, 2020 Share Posted August 3, 2020 Can anybody advice test to separate UV-A from UV-C radiation? I have only seen that postage stamps seems to exhibit different fluoresce with postage stamps and not always there big difference between 254nm and 365nm. Does 254nm or 265-280nm produce ozone? I have quartz lamps which produce ozone but UVC waves can be very short. https://chsopensource.org/category/multispectral-imaging/uv-fluorescence/page/2/ Link to comment
Cadmium Posted August 3, 2020 Share Posted August 3, 2020 Avalon, I am no expert on that, so I Googled it, according tho one link: "Ozone is produced naturally by UV light created from sunlight.UV light wavelengths shorter than 240 nm will create ozone via photolysis of the oxygen molecule.UV light wavelengths between 240-280 nm will destroy ozone via photolysis of the ozone molecule." https://www.oxidatio...on/uv-lamp.html Here is another link, these are all just from Google. so I recommend people investigate these questions because I am no expert, just curious also.I do have some germicidal UV for my aquariums, which I use occasionally, and I have no idea really for sure if they create much ozone or not.http://www.uvresources.com/blog/the-ultraviolet-germicidal-irradiation-uv-c-wavelength/ Link to comment
dabateman Posted August 3, 2020 Share Posted August 3, 2020 Can anybody advice test to separate UV-A from UV-C radiation? I have only seen that postage stamps seems to exhibit different fluoresce with postage stamps and not always there big difference between 254nm and 365nm. Does 254nm or 265-280nm produce ozone? I have quartz lamps which produce ozone but UVC waves can be very short. https://chsopensource.org/category/multispectral-imaging/uv-fluorescence/page/2/ Yes buy some rocks. There are some that only fluorescence under short wavelengths, 254nm. Others only at long wavelengths, 365nm. That could help you. Link to comment
Avalon Posted August 4, 2020 Share Posted August 4, 2020 Not much expert in mineralogy, can you name few rock examples? I recall earlier seeing different band ultraviolet photography including UV-C in someone forum post in room with furniture but can't find now. Link to comment
ulf Posted August 4, 2020 Share Posted August 4, 2020 You can find several by searching at eBay: Short wave fluorescent:https://www.ebay.com...cent+mineral+SW Long wave fluorescent:https://www.ebay.com...cent+mineral+LW Link to comment
Andy Perrin Posted August 4, 2020 Share Posted August 4, 2020 Can anybody advice test to separate UV-A from UV-C radiation? I have only seen that postage stamps seems to exhibit different fluoresce with postage stamps and not always there big difference between 254nm and 365nm. Does 254nm or 265-280nm produce ozone? I have quartz lamps which produce ozone but UVC waves can be very short. https://chsopensourc...escence/page/2/ There are some truly fantastic (in the sense of "unbelievable, and not in a good way") prices on that website. They are selling a tiny Arduino board to allow a Gigapan head to interface with a PC for 490€! Like, that must be about $40US of equipment there...and only very basic electronics and programming skills to put it together.https://chsopensource.org/product/shooting-adapter-for-pano-infrared-reflectography-bellini/ Link to comment
Avalon Posted August 7, 2020 Share Posted August 7, 2020 I guess calcite crystal is best mineral worth getting. It produces different fluorescence in UV-C, UV-B and UV-A. Will optical calcite work or it has to have impurities? https://www.ebay.com/itm/1pc-Iceland-Spar-Optical-Calcite-Quartz-Crystal-Mineral-Specimen/363059470341?hash=item548807e005%3Ag%3AUgUAAOSw3C5e2hh-&LH_BIN=1 Link to comment
colinbm Posted August 8, 2020 Share Posted August 8, 2020 I guess calcite crystal is best mineral worth getting. It produces different fluorescence in UV-C, UV-B and UV-A. Will optical calcite work or it has to have impurities? https://www.ebay.com...5e2hh-&LH_BIN=1 And in IR too....https://link.springer.com/article/10.1134/S0020168506110136 Link to comment
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