In Betty's Bay we talk about light pollution a lot. Not surprising, as here we have something so precious that it needs protection. Over the years I have noticed a decline in the quality of our night sky. Most of the light pollution is in the form of skyglow from neighbouring towns. For the first time I can now measure the amount of intruding light. It has made more sense to me to purchase a Unihedron Sky Quality Meter than a string of pearls.
On the morning of 12 October 2015 at precisely 02:00, I measured the sky quality from my home in Bass Road Betty's Bay and I wish we could have a drum roll here. I held my breath as I pointed the device to the zenith. How would Betty's Bay compare to other dark places in South Africa? I did not want us to be below average as I love our stars. I was thinking if only I could ask the owner of that very bright light down towards the sea and those who had blue alarm leds, where red ones could be just as effective and would also be more environmentally friendly, to switch off just for the measurement. That of course would have been cheating. Beep beep beep and I had my reading: 21.45 [Bigger numbers are better — Ed] The measured value is in magnitudes per square arcsecond. Now this sounds like Spanish but in comparison, values of 21.69 (Sutherland Observatory) and 21.95 (Hakos Observatory, Namibia) have been measured. These two sites are extremely dark places. I will keep on taking measurements and also do comparisons during holiday seasons and at different times of night.
Whatever you do, do not try to combat crime by having unshielded lights shining all night. It does not work and is just a big waste of energy. I live in the city where our nights have been turned into day and crime is spiralling out of control. I measured 17.20 from the darkest corner of my property. This means I can see only a few of the very brightest stars and planets. Bright lights that shine all night are a dreadful intrusion. Rather go for effective lighting with motion sensors or infra-red detection. This way, if there are patrols at night (or I am at my telescope!), any on/off lighting will alert to some kind of activity.
For this measurement to be included in a log of sky brightness readings, made with SQM-L meters, at various places in South Africa, I have to state the identity of my SQM-L: Unihedron Model no: 2.18 Serial no 8912
21.45 mags per square arcs at 02:00 on a Monday morning was not a bad start to the week. Our light pollution levels are not beyond the point where all hope of preserving the night sky has been lost. Maybe just maybe we can close in on Sutherland - if only we could get Kleinmond to play along as well.