dabateman Posted October 23, 2020 Share Posted October 23, 2020 Ok now I will have to image a candle. That has been on my todo list for a long time.I know the blocking of my filters. Andy you could try the same with the filter and imager. Link to comment
WiSi-Testpilot Posted October 23, 2020 Author Share Posted October 23, 2020 I made a further image. The filter is now 270 nm, bandwidth is 15 nm, shutter time was 500 ms, all other settings default.https://www.ahf.de/p...-bandpass?c=138Basically it is the same as at 250/20 nm, see #21.In the upper area of the image, in the background, you see the daylight leak through the living room window.Best regards,Wilhelm Link to comment
Stefano Posted October 23, 2020 Share Posted October 23, 2020 You may even try UVC LEDs in the future, even if a low-pressure mercury vapour lamp is much more powerful and efficient, and thus way better for UVC illumination. Link to comment
WiSi-Testpilot Posted October 24, 2020 Author Share Posted October 24, 2020 The spot at the top of the flame is an IR leak. Please see this thread for further informations:https://www.ultravioletphotography.com/content/index.php/topic/4153-candle-flame-with-uv-imager/page__pid__39418__st__20#entry39418Best regards,Wilhelm Link to comment
dabateman Posted October 24, 2020 Share Posted October 24, 2020 Wilhelm,What this does say is even with the IR leak you are still seeing a lot of UVC in the sides and bottom of the candle, which emits a very small amount of UVC. Once you get a good 254nm light source, I think you will be happy with this sensor. Link to comment
WiSi-Testpilot Posted October 24, 2020 Author Share Posted October 24, 2020 On my current PC I have not yet Excel, so the OD spectra are a bit raw. David, in the other thread you wrote:“Also he had dark water at 313nm. Thats not right. That is clearly IR high band leakage.” The water is not really dark, but water absorbs UV light:https://en.wikipedia...rption_by_water My question: is my water glass image right or not?Best regards,Wilhelm 250/20 nm 270/15 nm 313/25 nm Link to comment
Stefano Posted October 24, 2020 Share Posted October 24, 2020 Water starts to absorb in UV, but at 300 nm, depending on the source (they vary quite a bit) the absorption is the same than at ~500-700 nm, to give a wide range. A glass of water doesn't become noticeably dark until you go in the 900 nm+ range. At 850 nm, a glass of water (to my camera) appears still transparent. Maybe (if the darkness is not due to IR) your water is not pure (I guess it is tap water or water from a plastic bottle) and the ions in it absorb UV light. Distilled water may appear different. Link to comment
Andy Perrin Posted October 24, 2020 Share Posted October 24, 2020 Honestly, the water doesn't look all that dark to me in the image. It's not at all like what I see in IR. So this seems like a plausible result. It just shouldn't appear black until below 200nm. Stefano, remember your own early test with the water appearing quite dark just due to refraction effects? That could also be the case here. Link to comment
Stefano Posted October 24, 2020 Share Posted October 24, 2020 Stefano, remember your own early test with the water appearing quite dark just due to refraction effects? That could also be the case here.I didn’t think about this. Yes, it can be. If the background is quite dark, it can make water appear darker than it really is. Link to comment
WiSi-Testpilot Posted November 8, 2020 Author Share Posted November 8, 2020 A small update:I have not been able to take UV-C images of corona discharges at our power line so far, because it has been switched off for maintenance.The image shows the daylight leak with my 270 nm filter. Shuttertime was 0.5s.Best regards,Wilhelm Link to comment
WiSi-Testpilot Posted November 19, 2020 Author Share Posted November 19, 2020 My first image of Kassiopeia. The air wasn't particularly clear tonight. I hope that the camera will also show the Milky Way in the future. Shutter time was 1s.Best regards,Wilhelm Link to comment
Stefano Posted November 19, 2020 Share Posted November 19, 2020 Is this without filters (full-spectrum)? For one second of exposure, that's not bad at all. Here is what my camera can do with 60 seconds of exposure:https://www.ultravioletphotography.com/content/index.php?app=core&module=attach§ion=attach&attach_rel_module=post&attach_id=17275 https://www.ultravioletphotography.com/content/index.php?app=core&module=attach§ion=attach&attach_rel_module=post&attach_id=17276 Your sensor looks grainy, in a good way. It reminds me of paper (I never shot film, but I know that film, especially high ISO film is grainy, but it isn't like the noise in a digital camera, it is good noise). You may try subtracting a dark frame to attenuate this, assuming it is noise and not light pollution or haze in the sky. Link to comment
Andy Perrin Posted November 19, 2020 Share Posted November 19, 2020 Is this without filters (full-spectrum)? For one second of exposure, that's not bad at all. Here is what my camera can do with 60 seconds of exposure:https://www.ultravio...attach_id=17275 https://www.ultravio...attach_id=17276 Your sensor looks grainy, in a good way. It reminds me of paper (I never shot film, but I know that film, especially high ISO film is grainy, but it isn't like the noise in a digital camera, it is good noise). You may try subtracting a dark frame to attenuate this, assuming it is noise and not light pollution or haze in the sky.How did you avoid the star trails, Stefano? At 60 seconds they should be streaking a lot with most lenses? Link to comment
Stefano Posted November 20, 2020 Share Posted November 20, 2020 I don't know. If you look closely, you can see them. The version I posted has been resized, I can send you crops or even the original images if you want. Stars appear as short lines, not as points. Link to comment
Andy Perrin Posted November 20, 2020 Share Posted November 20, 2020 What focal length is that? Link to comment
Stefano Posted November 20, 2020 Share Posted November 20, 2020 I will check later on the original images, in the midtime I looked at a bunch of other images from this camera I saved on my phone, and they are all 5 mm. That should be the focal length at the minimum zoom. I looked at a fully zoomed-in image and there the focal length is 20 mm. So my camera does between 5 and 20 mm, and the images above should be 5 mm. Of course you have to take into account the small size of my sensor. 5 mm on a typical sensor would be super wide angle. I found the images on my phone. Yes, 5 mm (both). Link to comment
WiSi-Testpilot Posted November 20, 2020 Author Share Posted November 20, 2020 Is this without filters (full-spectrum)? For one second of exposure, that's not bad at all. Here is what my camera can do with 60 seconds of exposure:https://www.ultravio...attach_id=17275 https://www.ultravio...attach_id=17276 Your sensor looks grainy, in a good way. It reminds me of paper (I never shot film, but I know that film, especially high ISO film is grainy, but it isn't like the noise in a digital camera, it is good noise). You may try subtracting a dark frame to attenuate this, assuming it is noise and not light pollution or haze in the sky. Stefano,thank you for the information and the links.It's a full spectrum image. First I tried my 313 nm filter, but it didn't work.I took the picture in our garden. There was of course light pollution and also haze in the sky. The Milky Way was not visible with the naked eye. So I'll do it again when the sky is clear.Furthermore, the camera is very unwieldy. I'm trying to build a more mobile unit right now.Best regards,Wilhelm Link to comment
dabateman Posted November 20, 2020 Share Posted November 20, 2020 You have a ghost cable in that image. I like the star image. It has a nice feel to it. Too many of our stuff these days is too clean. Link to comment
WiSi-Testpilot Posted November 20, 2020 Author Share Posted November 20, 2020 Thank you.I bought a small Win10 PC (Orbsmart AW-08S)and a shorter ghost cable for the new setup. Link to comment
WiSi-Testpilot Posted November 23, 2020 Author Share Posted November 23, 2020 I would like to take UV-B images in daylight at 300 nm. Therefore I bought a 300/10 nm bandpass filter. The question is: is UV light available at 300 nm now in November?As a test object, I use our terrace roof. A part has UV protection, a part has not. Terrace coverage recorded with the Full Spectrum Alpha 6000 and the Baader U-Filter. Terrace coverage recorded with the 2020BSI camera, 300 nm and 313 nm filter. At 300 nm, the UV protection is hardly to see. I also tested the influence of glass at 300 nm. It is a double-glazed window. All images where made at the same day.It seems, that there is a small amount of 300 nm UV light superimposed with the leakage of the filter.Best regards,Wilhelm Link to comment
Stefano Posted November 23, 2020 Share Posted November 23, 2020 If you have some Hoya U-340/UG11/ZWB1 glass, try to stack it on the filter. Depending on where the leak is, this could help. Link to comment
WiSi-Testpilot Posted November 23, 2020 Author Share Posted November 23, 2020 Stefano, I don't really want to use glass filters. When the sun is shining strongly again, I will repeat the test. Link to comment
WiSi-Testpilot Posted November 24, 2020 Author Share Posted November 24, 2020 Back to the stars:this is a winter assignment. Edit: I've added the positions of two nebulae. Link to comment
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