A Closer Look at the CVEMS Exclusion Zone

The map included in the previous post showed roughly how much of the North Valley is protected by the 75-mile CVEMS exclusion zone for the Discovery Channel Telescope at Happy Jack, AZ. But I wanted to know more precisely just where on I-17 the boundary lies. Google Earth to the rescue! I put a thumbtack right in the middle of the observatory dome, which is visible in the screen capture below.

And here's a screen capture of the line drawn by Google Earth's measuring tool, stretched to approximately 75 miles and attached to I-17 ...

Finally, after precisely positioning another thumbtack at the intersection of I-17 and Daisy Mountain Drive in Anthem, I was able to reposition that measuring line to get an exact distance, good to 4 significant figures. As you can see from the following screen capture, that distance is 74.69 miles. That would put the exclusion boundary 0.31 miles (1637 feet) south of Daisy Mountain Drive. So we shouldn't expect to see any new CVEMS from that intersection to all points north.

In case you're wondering, if you swing that measuring line to the east, you'll find that most (but not all) of Desert Hills, Cave Creek, and Carefree are also safely in the exclusion zone.

Except for one caveat. The way HB 2543 is written, any CVEMS that is "onsite" will be allowed. For example, the CVEMS at the Anthem Outlet Mall is on the same property as that mall. Hence, it's allowed. What the bill excludes are the kind of CVEMS you see on rights-of-way adjacent to highways all around the Phoenix area. Most are not physically on property belonging to the companies using them for ads, and those are the CVEMS addressed by HB 2543.

So what would happen if the Road Runner Saloon decided to put up a CVEMS on their property? Answer: It would be allowed. Fortunately, most of the businesses north of Anthem are too small to afford a CVEMS. Large CVEMS like the one at the Outlet Mall cost $300,000, and use about $5000 of electricity yearly (not to mention maintenance costs). So if a small business like that did want a CVEMS, it would be in the size range that creates only a "small" amount of light pollution, and little interference for astronomy.