By Bill Irwin –
The ongoing cloudy and rainy weather eroded some of the observing opportunities this past fall. As we head later into the year, the earlier darkness makes viewing times more convenient. Observing is greatly reinforced by habit but many things conspire to interrupt the processlike having to go to work, unfavourable weather, and the effect of moonlight on the visibility of faint celestial objects. The folklore is that every time you get a new piece of astro gear the weather will be rotten.
On a wider basis, the real threat is light pollution, which appears to be getting exponentially worse. LED lighting has been a mixed blessing. It is more efficient, especially over incandescent, and is rapidly replacing other forms of night lighting both outside your home and inside. The advantages are many, including long life, no warm-up, good performance in the cold, dimmability, better utilization of the hydro waveform, and no mercury.
Unfortunately, the increased efficiency encourages people to put in brighter lighting. The impact of all this on animal night life and human circadian rhythms including melatonin has been well documented.
At night in the observatory or at a star party we use dim red lighting because it impacts your night vision the least. Our dark adapted (scotopic) vision becomes more sensitive to blue light at night. It scatters more readily within your eye and can trigger what is called disability glare. This can get worse with age. Just think of those bright blue LED headlights coming at you.
LED lighting can have a large amount of blue content. This affects you indoors at night as well. The bulbs you can buy locally have a colour temp rating on the box and usually on the bulb as well. The lower the colour temp rating the more the spectrum shifts to the red. I usually choose soft, white 2700K bulbs. I find they are the most like the benign incandescent bulbs we grew up with. I find even 3000K bulbs to be too bluish for my taste. During the daytime, when your vision sensitivity shifts towards the yellow, the blue glare is much less of a problem and 3000K bulbs or higher could be used in your shop, etc.
I highly recommend downloading the small program called f.lux for your computer. It allows you to adjust the daytime and night-time colour temp of your monitor and automatically dims the display during the dark hours. I have my monitor down to candlelight brightness at night.
Since our senses generally respond logarithmically to intensity changes, even a small amount of reduction can have a large effect.
This is yet another adaptation we have to consciously make to the power that technology has given us.
We will get back to the stars next time. They, too, have colours.
Observing sessions at the Bells Lake Observatory are on short notice due to the weather, so if it looks like it’s going to be a clear night you can give me a call at (250) 620-0596 or contact me at email@example.com.