What color is a telescope? And what does it matter anyway?
Back in the day (AKA 100 years ago), the 20-inch Van Vleck telescope was painted black. I believe the rationale was that astronomers wished to keep the space in the dome as dark as possible; naturally a dark paint was in order. More scientifically, the color black absorbs light. Stray light in the dome is something to consider and painting a telescope so that it can absorb stray light to the maximum seems rather logical.
Today the telescope is painted white–or more specifically, a slight off-white. The rationale here is that white reflects light. Because white does not absorb light like the color black does, a white telescope will be cooler than a black one. This is important to regulate the temperature of the instrument. The mount however is still kept at a dark hue. As for why the dome itself is painted white outside, well the story is not too different.
Now for all you extreme telescope enthusiasts out there who want to know the specific paint colors, I’m talking color codes and more here, you are in for a fun story.
A while back, Bill Herbst, his wife, and a consultant from the Wesleyan Art Department decided on the colors to paint the telescope: Dakota Shadow for the mount and North Star for the tubes. The Dakota Shadow was a bit too light, so a request was put in for Dark Dakota Shadow with no white added.
Over the summer however, while working on the telescope restoration, Fred received a mis-mixed batch of paint. To remediate the error, the Cromwell Paint Spot shop named a new paint color–with the proper mix of green, yellow, black, and white–for Fred and put it in their system as “Telescope Green.”
Matt and I called the Paint Spot to investigate further. We spoke to a very nice sales representative who looked up the paint color for us. He didn’t recognize “Telescope Green” off the top of his head, but when we gave him the custom code he found it immediately! The rep said that the shop still has Telescope Green paint in stock, but because it is a custom color, we would need to bring in the can with the lid and the code to actually get the paint.