Visiting the Carolinas to see the Aug. 21 solar eclipse? Better book your room now.

Visiting the Carolinas to see the Aug. 21 solar eclipse? Better book your room now.

CHARLOTTE, NC (Bruce Henderson/The Charlotte Observer) - Bookings in advance of the solar eclipse that will sweep across western North Carolina and South Carolina on Aug. 21 show rooms are available but going quickly.

A survey last Friday of 11 hotels in Columbia, which is directly in the path of total eclipse, showed all rooms booked for the night before the eclipse, said Experience Columbia SC, which markets the city.

Rooms might still be available at other hotels in the area, said spokeswoman Andrea Mensink, who recommends that visitors directly check hotel chain websites.

Some rooms are also still available on the short-term rental site Airbnb, she added. The San Francisco-based company tells Charleston's Post and Courier that it expects its biggest night ever in South Carolina, with nearly 7,000 rooms booked across the state.

Bookings for Aug. 20, the night before the eclipse, are expected to be nearly five times higher than usual. Charleston accounts for 2,500 of the houses booked on the weekend of the eclipse, more than Columbia and Greenville, S.C., combined.

Airbnb said Friday that more than 1,600 rooms have been booked in the path of total eclipse in North Carolina, a 475 percent increase from the same time the previous week.

Airbnb argues that allowing home rentals gives cities more flexibility to absorb a crush of visitors. A Charleston task force is debating how to handle temporary rentals, which critics say drive rents higher and change the character of the city's neighborhoods.

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The eclipse where you live

While much of North Carolina will be outside the 70-mile-wide path of total eclipse, a partial eclipse will be visible across the U.S.

This animated website details, by ZIP code, what you'll see and when you'll see it.

Uptown Charlotte, for example, will see 97.9 percent of the sun covered by the moon, peaking at 2:41 p.m. on Aug. 21.

Solar energy will dim

The roughly 90 percent partial eclipse that most of North Carolina will see is enough to have an impact on the state's solar industry, which is second-largest in the U.S.

If Aug. 21 is very sunny with low humidity, Duke Energy calculates, solar panels connected to its grid in North Carolina could lose 1,500 megawatts of energy in the last hour of the eclipse. That's enough to power 250,000 homes. The moon will partially cover the sun for nearly three hours in the state.

Duke owns or buys 2,500 megawatts of solar energy in the state.

Solar power will ramp back up later, spokesman Randy Wheeless said, but during the eclipse Duke will rely on its natural gas-fired and hydroelectric power units to make up for the lost solar energy.

The right eclipse glasses

Special solar filters are required to safely view the eclipse, including its partial phases. But NASA warns that not all eclipse glasses meet safety standards.

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Eclipse glasses and hand-held solar viewers should be printed with a certification that they comply with an international standard, ISO 12312-2, the space agency says. The manufacturer's name and address should also be printed somewhere on the product.

Filters that are more than three years old, or have scratched or wrinkled lenses, shouldn't be used.

The American Astronomical Society vouches for five manufacturers that meet the standard: American Paper Optics, Baader Planetarium (AstroSolar Silver/Gold film only), Rainbow Symphony, Thousand Oaks Optical and TSE 17.

Ordinary sunglasses won't protect your eyes while looking at the sun, experts say.

NASA has distributed free, certified eclipse glasses to libraries nationwide. The Charlotte Mecklenburg Library's Beatties Ford Road, University City and Harrisburg branches are participating, the agency said.

A safe alternative to eclipse glasses is a pinhole projector, NASA says. A small hole in a piece of paper, such as a pencil hole, will let sunlight stream onto a makeshift screen, such as a second piece of paper or the ground. Watch only the screen – don't look at the sun through the pinhole.