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| Taipei City core is a 9.9+ Bortle rated light polluted center. Light pollution is the most heavy during the early night when most lights are on. Imagine a tall skyscraper with 250 families and light shining through their 500 windows until they fall asleep. Now imagine 350 skyscrapers with 175,000 lighted windows! City lights include incandescent, fluorescent, sulfur, mercury vapor, and LED styles. |
LED Light Pollution Creating Atmospheric Haze Craze"The rising tide of energy-efficient LED street lighting could prove a double-edged sword in terms of light pollution impacts on wildlife. LED technology lends itself to control in terms of both beampattern and dimming/switching; therefore careful deployment of LED lighting using higher levels of control could abate some of the problems caused by light pollution. However, the replacement of HPS street- and area lighting with LED could introduce a major change in the color of urban skyglow. The higher blue content in LED lighting is more subject to scattering in the atmosphere, especially by cloud cover, thus increasing skyglow. In addition, the blue spectra have a greater impact on melatonin production and could further disrupt sleep patterns in diurnal animals, including humans."
Quick Solutions
The quick solution is only a small temp fix, i.e. to filter out the blue LED spectrum in the night sky. Filters are available for cut and broadband selections and the new IR are specially designed to penetrate atmosphere as well. It will be challenging for telescopes to shoot through such heavy light pollution, however the new digital telescopes are coming, such as the Unistellar eVscope (which does not accept filters) that are designed to handle light pollution in urban core areas.
Effects of Light Pollution
"Living in a light polluted urban area does not mean you can't observe the deep sky. However keep in mind that only a handful can be seen and details of them will be far less impressive. The following images illustrate the effects of light pollution on some of the brightest deep sky objects, which are observed using the same telescope from different locations. In this particular example - The Great Andromeda galaxy through a large telescope."
Light pollution affects fainter DSO such as distant galaxies even more dramatically. Above is how the Virgo galaxy cluster may look through a large telescope in different locations. Strong light pollution will make many fainter galaxies invisible.
Heavy Light Pollution Plan
Set up a plan for observing deep sky objects from an area with a moderate light pollution. Focus on objects like open clusters, double stars, brightest emission nebulae and bright planetary nebulae with high surface brightness.
Tips for Light Polluted Regions
* Early morning hours people have their lights off and are sleeping
* Image on nights of less smog - the combination of smoke, fog, and light pollution
* Shield from the direction of the heaviest light pollution sources
* Cut spectroscopic wavelengths: smog, haze, atmosphere/light pollution sources
* Check predictive maps for nights with the least pollution
* Keep a monitor on the ratio of humidity to air pollution
* Atmospheric contaminants can act as a reflective shield to the night sky
* Monitor particulate matter air content, less content offers greater transparency
* Use low noise CMOS sensors
* Look for times of minimal dust suspension
* Filter background radiation with image processing
* For extreme light pollution filters, consider the Hydrogen-Alpha line
* Use long pass filters, 50% transition from blocking to passing at about 640nm
* Consider the entire line of cutoff filters, inclusive of 742, 807, etc.
* Avoid weekend imaging sessions when night lights increase
* Buy a light pollution sensor and monitor nightly results to detect patterns
* Addtl. full scale image processing
