WiSi-Testpilot Posted January 27, 2020 Share Posted January 27, 2020 Since I started playing with UV photography I have been looking for corona discharges. Looking through pictures from last summer, I found some. First I thought it were reflexes.I will try it again.Sony Alpha 6000, Pancake Lens SEL16F28, Baader U-Filter, Daylight (12:37, lunchtime), F/3.2, 1/60 S, ISO 320.Best regards,Wilhelm Link to comment
Cadmium Posted January 27, 2020 Share Posted January 27, 2020 I think it is just sunlight being reflected off the glass glaze on the ceramic insulators.There is also some kind of reflection off other things in the photo, not sure what those are made of or not. Link to comment
Stefano Posted January 27, 2020 Share Posted January 27, 2020 Take a look here: https://www.google.com/url?sa=t&source=web&rct=j&url=https://hackaday.com/2016/07/06/seeing-the-truly-invisible-with-diy-shortwave-uv-imaging/&ved=2ahUKEwj34YTQ_KTnAhVFLlAKHXKvA7AQFjAAegQIAxAB&usg=AOvVaw052B62a6hJiJKJPdgMoUpy&cshid=1580169121535 I may be wrong, but from what I know corona discharges are only visible in very deep UV (SBUV, Solar Blind UV). Link to comment
OlDoinyo Posted January 27, 2020 Share Posted January 27, 2020 I second this. One would not expect corona discharges off an insulator stack--that makes no sense. These are specular reflections; in the middle frame they are distorted by lens coma. Corona discharge is usually photographed below 280 nm, whereas you are lucky to get fown to 340 with the kind of lens/filter combination you used here. Link to comment
WiSi-Testpilot Posted January 28, 2020 Author Share Posted January 28, 2020 Ok, sorry, probably you are right. But I will check it as soon as it is dry outside.Best regards,Wilhelm Link to comment
dabateman Posted January 28, 2020 Share Posted January 28, 2020 Try again on a cloudy day. Or if you can at night. Then for sure it would be from the lines and not the sun. I may have to see if I can see anything in low UV from my near by station. I just don't like the idea of standing outside for too long with a tripod. People around here are jumpy and might think I was up to something on the power lines. Link to comment
nfoto Posted January 28, 2020 Share Posted January 28, 2020 These are reflections off the insulator with a healthy amount of lens coma added. Repeat your photography at night time, preferably on a cloudy night with *no* rain . But probably won't show much as one probably needs resolving the deeper end of UV to show the discharges. Link to comment
WiSi-Testpilot Posted January 30, 2020 Author Share Posted January 30, 2020 Thank you very much for your answers.Today I cycled to our neighboring town of Stadtlohn to the Power Distribution Station. It is located at a former railway line, which is now used as a bicycle path.The isolators are made of glass. As you already described in the articles above, there are reflections, not corona discharges.Best regards,Wilhelm VisNikon Coolpix S3200, F/3.5, 1/640 S, ISO 80 F/5.5, 1/640 S, ISO 80 UVSony Alpha 6000, Lens SEL16F28, Baader U-Filter, F/4.5, 1/50 S, ISO 1600 F/2.8, 1/125 S, ISO 2000 Link to comment
Andy Perrin Posted January 30, 2020 Share Posted January 30, 2020 Still nifty to see one of these stations in UV-A! Link to comment
Stefano Posted January 30, 2020 Share Posted January 30, 2020 I can be wrong, but isn't the corona blue-violet in air? So, if it emits visible light, can it emit long-wave UV light as easily? Link to comment
Andy Perrin Posted January 30, 2020 Share Posted January 30, 2020 Stefano, I think it does emit some blue. In fact when I googled most of the spectra online look like this:https://www.researchgate.net/publication/233843861_Complexity_Investigation_in_the_Electrographic_Images_of_Ionic_Solutions/figures?lo=1 Etc Link to comment
Andy Perrin Posted January 30, 2020 Share Posted January 30, 2020 I am not sure why people talk about imaging it in UVC based on those spectra. Possibly it is because they are interested in OH radicals rather than the nitrogen? One thing I am sure about is that you can’t take UVA or visible pics of corona in the daytime because the sunshine will drown out the light from the corona. Possibly UVC imaging is an attempt to get around that issue. Link to comment
OlDoinyo Posted January 30, 2020 Share Posted January 30, 2020 It is because the OH A-X line falls in the solar-blind range, which enables it to be photographed in the daytime (during regular working hours) without interference from sunlight. Otherwise, it would be necessary to do such inspection work at night. The corona discharges are a sign of defects in or damage to the insulation. Link to comment
Stefano Posted January 30, 2020 Share Posted January 30, 2020 If someone can, build a “corona machine”, with a voltage multiplier, a Van de Graaff generator, or something that can generate a very high voltage. Use special care with transformers if you decide to use them, since they can provide a dangerously-high current for a prolonged period of time. Make sure to generate a strong electric field (maybe 1 MV/m), but not high enough to make arcs. You should be able to hear a sizzling sound and see a blue-violet glow. BE CAREFUL WITH ELECTRICITY Link to comment
dabateman Posted January 31, 2020 Share Posted January 31, 2020 If someone can, build a “corona machine”, with a voltage multiplier, a Van de Graaff generator, or something that can generate a very high voltage. Use special care with transformers if you decide to use them, since they can provide a dangerously-high current for a prolonged period of time. Make sure to generate a strong electric field (maybe 1 MV/m), but not high enough to make arcs. You should be able to hear a sizzling sound and see a blue-violet glow. BE CAREFUL WITH ELECTRICITY Or just buy an off the self plasma ball. I have a plasma plate. I thought I posted images somewhere. But may have to repeat it to see if it outputs UVC, now that I have the imager. Link to comment
colinbm Posted January 31, 2020 Share Posted January 31, 2020 The plasma ball is inside a glass ball........what glass is it....? Link to comment
Stefano Posted January 31, 2020 Share Posted January 31, 2020 Do plasma balls contain air or other gases? This can change the emission. Also, does the pressure change the emission, like in low and high pressure mercury or sodium lamps? Link to comment
Andy Perrin Posted January 31, 2020 Share Posted January 31, 2020 I think they must be near atmospheric pressure because think how dangerous a pressurized glass ball would be to sell to children... Update: Wikipedia confirms this; it’s atmospheric pressure noble gases in a glass ball. The glass probably absorbs all UVB and C. Link to comment
NA_joey Posted April 15, 2021 Share Posted April 15, 2021 Since I started playing with UV photography I have been looking for corona discharges. Looking through pictures from last summer, I found some. First I thought it were reflexes.I will try it again.Sony Alpha 6000, Pancake Lens SEL16F28, Baader U-Filter, Daylight (12:37, lunchtime), F/3.2, 1/60 S, ISO 320.Best regards,Wilhelm https://www.nasa.gov/langley/business/nasa-langley-s-ultraviolet-corona-detection-system-lifts-off-on-drone the spectrum is 240 - 310 nm most deception is done in. you need a monochrome camera to record in UV-C a industrial camera monochrome camera or Astronomy Camera, Microscope camera monochrome. Joey Link to comment
WiSi-Testpilot Posted April 15, 2021 Author Share Posted April 15, 2021 Hello Joey,https://www.ultravio...ra/page__st__20 the topic is still on my to do list. As soon as it gets warmer in the evenings, I'll try it again. Recently I was at the power line with my bike. Only the 110 V line is in operation at the moment.Best regards,Wilhelm Link to comment
Andrea B. Posted April 24, 2021 Share Posted April 24, 2021 Joey, thanks for that link. The NASA drone UV detector is very cool! Wish some of us could get one of those to try out. I like seeing how drones are used like that for some scientific or engineering use. When we got the solar panels last summer, they used a drone to perform a preliminary roof inspection and to map the roof. Very neat. They sent us some of the photos b.c. I wanted to see them. It was early pandemic, so I couldn't get too close to see how the drone was operated. But the drone operator was very good -- and having some fun too. I really do not want to see drones used to deliver packages to my doorstep. LOL !! No thank you. Link to comment
SteveE Posted April 24, 2021 Share Posted April 24, 2021 Let's hope they are smart enough to not deliver cameras and lenses by drone.However I'm not going to be placing any bets on their shipping acumen.My A7III came with its retail packaging just rattling around loose in a considerably larger box.I once got a single SD card in a box that was larger than a cubic foot. Link to comment
Andrea B. Posted April 24, 2021 Share Posted April 24, 2021 W.r.t. corona discharge, I was reading about this and learned that Solar Blind UV cameras are used for detection by maintenance crews. Here is a link to one example of a Solar Blind UV camera: https://www.findlight.net/imaging-and-vision/cameras/imaging-spectroscopy/corocam-7-professional-solar-blind-uv-corona-cameraWonder how much that costs? Link to comment
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