If those symptoms, or headache, are severe, he said, "I have a little bottle of oxygen and I hook you up to Greg's Oxygen Bar and get you down the hill."
Authorities urge summit visitors to use four-wheel drive vehicles because of the steep, rough road, and to respect the altitude at the summit, where temperatures often get down to freezing. Kids younger than 16 and anybody with health problems are strongly discouraged from going higher than the visitor center.
The cautions don't convince all, though.
"Here's one of those four-wheel drive Mustangs coming down, and this one's a convertible," Brown noted with sarcasm on our way up.
At the summit, we donned parkas provided by our guide. For my early-June visit, the temperature was in the upper 30s, with winds to 20 mph. Fingers quickly numbed. The wind was 83 mph a few days earlier.
The combination of excitement and low oxygen seemed to transform the tour group into giggly schoolkids, gawking at the summit's moonlike landscape dotted with gleaming observatory domes.
I ran to get a photo of the mountain's sunset shadow against clouds below, but quickly stopped when my heart pounded and breath ran short. But just stopping to gaze was rewarding.
"Oh, wow! Look at the clouds, and the clouds above the clouds!" said Shelley Burr, a Boeing employee visiting from Seattle. "You don't have words for this. It's the top of the world!"
After a half-hour of wild photo snapping, Brown called out, "Look, Gemini Northern (observatory) is rotating, and Keck has their doors open!" The observatories were opening for the night. It felt like a sci-fi movie set.
It would be a shame to get up in that clear air and not wait for stars to come out. So we drove back to the visitor center where Brown set up an 11-inch-wide telescope for our own star party, which included both the Northern Star and Southern Cross in one swivel of the head.
Saturn's rings drew "oh, wows!" and at least one OMG, and hot chocolate and homemade brownies revived us.
On the dark road back to the Kona hotel strip, Brown suddenly braked the van to point out the Big Island's active volcano. "Look, over near the base of Mauna Loa, see that red glow? That's Kilauea!"
Whoa. The glow from lava from the planet's bowels capped off the night, and brought us all back to earth.
IF YOU GO:
TOURS: I took the Mauna Kea Summit and Stars Adventure ($200, including picnic dinner and one-hour stargazing party) with Hawaii Forest & Trail (800-464-1993 or http://www.hawaii-forest.com ). The 14-passenger van left the town of Kailua-Kona at 3 p.m. and returned around 10:30 p.m., with about 45 minutes to watch sunset at the summit. A guide provided details on natural, cultural and geologic history; fellow passengers agreed it was worth the price.
A sampling of other tour operators:
Mauna Kea Summit Adventures offers a 15 percent discount off the $200 fee for early bookings in off-peak times; 888-322-2366 or http://www.maunakea.com.