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| richard.cs:
--- Quote from: james_s on May 18, 2021, 05:22:48 pm ---I agree, more even lighting would allow the use of less light to achieve the same result. The law says no light emitted above 90 degrees though which effectively bans drop-lens diffusers, and like many laws, it was based on good intentions but brings unintended consequences. --- End quote --- It's perfectly possible to make optics with a sharp cutoff just below 90 degrees and which gives good, even illumination. Optimally the beam pattern should give less light per unit angle straight down and progressively more light per unit angle near to the cutoff. This ensures that the light per length of road is roughly constant. Such fittings exist, and work well, but there is an optimal pole height and spacing for them. Retrofitting them onto existing poles designed for lights with a different pattern often gives crappy results.* The optical design is easier (cheaper, more compact, etc.) with taller and/or closely-spaced poles because the cutoff angle can be lower, and the brightness ratio between the centre and the edges less. * But is very common. Adding new poles to reduce the spacing is expensive as you have to dig up lots of cables, etc. Changing the poles, generally to taller ones, is cheaper but still much more than just slapping a new fitting on the end. In the UK there are plenty of 1930s and earlier light poles with modern fittings on top**, and often the resulting light pattern is pretty poor. ** e.g. https://goo.gl/maps/SH7Tcoy2PRnfy5888 |
| rdl:
Yeah, it would be nice to get more use out of my telescope. --- Quote from: Sal Ammoniac on May 18, 2021, 05:26:58 pm ---Why do we feel the need to light up everything at night? We're doing irreparable harm to many animal species that evolved in dark night skies. Human hubris at work... :palm: --- End quote --- |
| james_s:
--- Quote from: Sal Ammoniac on May 18, 2021, 05:26:58 pm ---Why do we feel the need to light up everything at night? We're doing irreparable harm to many animal species that evolved in dark night skies. Human hubris at work... :palm: --- End quote --- Because people like it, it makes them feel safer, it looks nice, it does make driving significantly safer, it eliminates many of the dark places where crime festers. I do think we could do with much less of it though, generally speaking light levels are much higher than they need to be, and at least in residential neighborhoods like mine the lights are spaced far too far apart to be of any real use. Street lighting could be 1/4 or even less lumens than is typically used and it would still accomplish the goals. That and motion detectors that turn on lights or make them brighter only when there is somebody in the area that is being lit up. |
| Red Squirrel:
--- Quote from: Sal Ammoniac on May 18, 2021, 05:26:58 pm ---Why do we feel the need to light up everything at night? We're doing irreparable harm to many animal species that evolved in dark night skies. Human hubris at work... :palm: --- End quote --- That's a good point too, I get that there is a safety aspect, but people survived fine before lights. We need to stop bubble wrapping society. I think a good compromise would be occupancy sensors, roads/area that have no activity the lights would turn off and only come on (slowly dim and not sudden on) if they detect activity. Not really sure what the best way of doing that would be though, simple infrared sensors would trigger every time a bear or large dog passes by, lasers that are higher than a bear on 4 legs could work but pose a risk to eyes. |
| PlainName:
I ain't gainsaying you, but this kind of thing doesn't help your cause: --- Quote --- people survived fine before lights --- End quote --- People survived fine before cars. People survived fine before mobile phones. People survived fine before landline phones. People survived fine before post. People survived fine before concrete. ... The are LOTS of things people survived fine before. Some of them are actually useful and/or made life better. The ability to stay up after dusk and keep going until dawn, whether that's good or bad, is primarily down to lights. |
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