Palomar has gone green. Ok, the dome is still white (really, this is just a visual metaphor), but the observatory is working to cut its use of electricity. One of the ways that this is happening is through changes in the lighting behind the back-lit displays for visitors.
Here's one of the many displays in the observatory's visitor center:
It shows a supernova remnant known as Simeis 147. The image comes from the second Palomar Sky Survey and was nicely processed by Davide De Martin over at Sky Factory.org. (Visit his site there's lots of cool stuff there!)
The fixtures for the displays are more than 50 years old. Until recently each of the 30 displays had six 15-watt bulbs on the inside. On average they are turned on 8.5 hours a day. With the observatory being open to the public 363 days a year, the displays consume over 8.3 megawatt hours a year!
We’ve just made the switch to 15-watt compact fluorescent (CFL) bulbs. They are so much brighter than the old incandescent bulbs that we are able to drop each display down from six bulbs to two – cutting our energy use by 33.3%. That's a savings in money and a reduction in the amount of greenhouse gases that would otherwise be produced. So we get to show off cool photos of supernovae and telescopes but in a greener way.
Here's the display from above opened up. Inside is six 15-watt incandescent bulbs:
Now replaced with just two 15-watt CFLs:
As you can see the CFLs are brighter. It may look like all six bulbs are on in this shot, but it is just 2 of the CFL's and 4 dead incandescents (to fill the otherwise empty sockets).
If you are making the switch at home remember that a 15-watt CFL is as bright as a 60-watt incandescent bulb. Be sure to use a lower wattage on those CFLs to prevent overlighting and any extra contributions to light pollution.
To reap even greater savings and cut on light pollution, remember to use the off switch.