Science | Skywatch with Bill Irwin

By Bill Irwin –

Well, did Santa leave a long slender package hiding a telescope under the tree? Or maybe a short stubby one with some new binoculars or a moon globe or something?

I’m afraid some of you might have gotten yard lights for Christmas. Maybe one of those intense blue LED ones that prey on your blue sensitive, dark adapted, night vision. Your eyes much prefer the warm red glow of Rudolph’s nose, I suspect.

A typical yard light is considerably brighter at a 1 km distance than the brightest celestial objects like Jupiter or even Venus. Night lighting is often necessary, but why do we have to look at the bulb, which is usually way brighter than what it is trying to illuminate?

The LED lighting revolution is a bit of a mixed bag. Yes, they are more efficient in their use of power, but that can lead to the use of more and brighter ones. The colour is also an issue.

Good old incandescent bulbs produce their light from a glowing filament, which, by its nature, produces a continuous spread of colours like in a rainbow. Maybe a bit weak on the violet end. Gas discharge, fluorescent, and LED lights have bright and dark portions in their spectra, so some colours are favoured.

Since LED lights are here to stay, manufacturers have been working on the colour rendering index or CRI to get them to behave more like the incandescents we grew up with. Whether I actually grew up is another question that can’t be debated here. Maybe out under the stars.

So, I always buy the 2700 K colour temp bulbs, especially for after-dark use when our eye sensitivity naturally shifts to the blue and we need more red. I even saw a new breed of dimmable bulbs that actually shift their colour more toward the red as they are turned down, just like an incandescent. So, there is hope.

A lot of the problems of yard lighting and so called light trespass can be solved with proper shading, so the light is directed where you want it and not glaring in your eyes or casting light above the horizontal where it is entirely wasted, lighting up all the dust in the atmosphere.

On the way out of Kamloops, BC is a retirement village called Tobiano. When driving by after dark, I could see all the streets perfectly but couldn’t see any light bulbs. When I investigated, I saw they used deep recessed fixtures with some kind of fairly ordinary bulbs. It was very effective. Venus will become prominent in the evening sky as we roll on towards spring. as Jupiter and Mars will dominate the southeastern predawn sky. It’s a big year for Mars as we head towards its close opposition in July. Close oppositions are low in the sky, so observing will be hampered by the atmosphere and its turbulence. Sometimes, too, these perihelic oppositions (closer to the sun) can give rise to dust storms on Mars that obscure the fine detail. That makes seeing Mars all the more fascinating and challenging. Even though it is very small and surface details are blotchy, even with superb optics, those moments when the image settles and you connect with the reality of the solid surface of another world, give an aesthetic experience that can’t be had any other way. There is also the infinitesimally small, but non-zero chance you might pick up some poorly shielded yard lights on the surface.

I know it’s the cold season, but our observatory does have a heated warm room. You are welcome to join us. Orion and the bright stars of winter will be around for a little while yet and then there’s that big reverse question mark of Leo the lion rising in the east, a sure sign of spring.

As usual, you can come right down to the arena here at the Bells Lake Observatory. Contact me at (250) 620-0596 or irwin8sound@gmail.com.

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