FORT DAVIS - In the high mountains of a wild desert, day drains from the sky and night lights appear like halos on the horizon.

There's no moon. Just Mercury chasing the setting sun in the west, Jupiter rising to the east and another golden light emerging on the northern horizon.

The view from the McDonald Observatory, considered the crown jewel of the University of Texas System, includes the glow from the Permian Basin oil field, incandescent with the work of 24-hour drilling, fracking and gas flaring.

Four in every 10 drilling rigs working in the U.S. are in the Permian Basin, and the prolific oil province is creeping closer to the observatory, where astronomers depend on the veil of desert night in the Davis Mountains of the Big Bend region.

"It just feels like a tidal wave coming at us, because you know, 10 years ago, we looked up to the north and we saw a dark starry sky and now we see this glow," said Bill Wren, special assistant to the observatory superintendent. The oil field lights don't hinder astronomical research - the McDonald Observatory remains a place of exceptional darkness. The sky's zenith, where astronomers look to the edge of the observable universe, remains free of light pollution.

What worries astronomers is the idea that the oil field, the most productive in the U.S., will keep marching toward it, and worse, glowing brighter and chewing up more of the sky.

A new light pollution measurement just released by the observatory shows how much brighter the night sky is than it should be - 18.5 percent above the background glow of natural features.

"It's only down toward the horizon where it's polluted, and astronomers aren't pointing the telescopes down close to the horizon," Wren said. "They're observing high overhead. It's still an extremely dark sky for astronomy. It's a little spooky to see that glow growing and coming this way."

The observatory's new light pollution measurements come as it teams up with the oil and gas industry. West Texas' largest oil and gas group just released dark-skies recommendations for the first time after a long collaboration with the observatory. The observatory also has partnered with Houston-based Apache Corp., the oil and gas company whose 3,000 planned wells are the source of the most recent light pollution threat.

Apache in September announced it had discovered a new field with the equivalent of 15 billion barrels of oil and gas, the Alpine High. It's the closest part of the Permian to the observatory, about 30 miles away, and the problem is this: The closer a light source is, the brighter it appears.

"The Alpine High play is particularly worrisome to us because of its proximity," Wren said.

Mutual friends introduced Wren to Apache executives after the Alpine High announcement, and three company vice presidents met with Wren for the first time last fall at Southside Market & Barbecue in Bastrop.

Over barbecue, Wren used a PowerPoint presentation on his laptop to walk the executives through the observatory's work and sky glow concerns; they shared information about the company's land position in Alpine High, 60 miles that stretches across the southern half of Reeves County.

Since then, Wren has climbed the drilling rigs of all of Apache's contractors in the region. He's helped readjust lighting so it points down instead of sideways or up to the sky, where it creates light pollution.

He's looked a blueprints of new offices in Pecos to make sure the lighting is dark skies friendly, and he's given presentations on dark skies to the service companies Apache hires.

In December, 13 Apache corporate officers visited the observatory, including CEO John Christmann.

Every week, Apache's health and safety team checks 612 bulbs on everything from portable light plants to drilling rigs to make sure they are dark-skies compliant said Marcus Buton of Apache.

"We look at every blasted bulb in the air, and that is the truth," said Buton, who spoke recently at the Responsible Shale Energy Extraction Symposium in Dallas. "We want to show we can do things differently and do it right."

More vexing is the problem of natural gas flaring.

It's a common practice in fields like the Permian where the most profitable target is oil, and a particular issue when new wells come into production. Apache is spending $500 million this year on infrastructure such as pipelines and gas plants, but even companies that build pipelines to carry natural gas to market usually flare gas at the start of projects.

Apache has flared or vented 36 percent of the natural gas it produced in Reeves County in the past three years, according to an analysis of data reported to the Texas Railroad Commission.

That's far higher than the statewide average. Less than 1 percent of gas produced in Texas is flared or vented, according to the Railroad Commission, whose data don't distinguish between the flares that burn gas and the more environmentally harmful venting, which simply releases the gas to the atmosphere.

Apache's flaring and venting rate has been dropping, from 66 percent in 2014, to 38 percent in 2015, and 9.8 percent last year, the data show.

As the company has brought on new wells in Alpine High, it could start selling the oil, but has shut them in instead to wait for gas pipelines. So far, it has drilled 32 wells in Alpine High and shut in 16 of them, said Joe Brettell, an Apache spokesman. Of the other wells, six are being tested and 10 are drilled but awaiting completion.

"Flaring is a temporary but necessary part of developing a new field," Brettell said. "We anticipate the drop will continue as we progress in building out our infrastructure."

Apache expects to start moving some of the gas from the Alpine High through pipelines to market this summer.

It said it cannot, however, make flaring vanish from the desert landscape.

The Permian Basin Petroleum Association released a set of guidelines it's been working on with the observatory - recommendations that if oil companies flare gas, they do it in an incinerator that conceals it better than the typical open flame.

"The dark-skies concept is not new, but the increased level of activity is," said Ben Shepperd, president of the Permian Basin Petroleum Association, who considers the observatory a treasure for West Texas.

Apache tested an incinerator at one of its Alpine High wells, but said it didn't work well with the high flow rate. Brettell said the company would consider using the technology if it worked, but it didn't in this instance.

The upshot is that at least some gas flaring will continue to be visible in the Alpine High, and incinerators will not be used.