Pulling the Primary


Turn right at Alamogordo, pass High Rolls, and 9000 feet up into New Mexico’s Sacramento Mountains, turn right again and go 15 miles along a narrow switchback two-lane, turn off on the Apache Point road, pass a pond, and hit the dead end at Apache Point Observatory, a cluster of utilitarian buildings.   Inside one building is a little 2.5 meter telescope.  The telescope sits on a man-made ledge that’s cantilevered off the side of the mountain and looks out at the White Sands Missile Range; the white sands are gypsum that dusts the telescope and mirror. The telescope, dedicated to the biggest digital survey of the sky, has been up there since the mid-1990’s, and every year its mirror has to be taken off and cleaned.  In the digital survey business, astronomers get all the glory but my personal true loves are the guys who take the mirror off the telescope.

“Guys” is generic, men and women both, six or so of them.  They live not less than 45 minutes away.  “This is a good job for out here,” they say, and they feel lucky to be working on a telescope and not the cooling units for refrigerated trucks.  Age range is from 20 to around 60.  Dress is workshoes, leather gloves, jeans, t-shirts, flannel shirts, sweatshirts, worn in multiple layers to be taken off and put on, depending on the quickly-changing cloud:sun and clear:rainy ratios.  They work pretty much in the open: the building in which the telescope sits has effectively two open ends, one of them overlooking a view the size of Massachusetts.  They’re aware of safety — “don’t put your finger in that nitrogen unless you want it frozen off” – and “if someone gets hurt and can’t be fixed with a Leatherman and duct tape, just roll ‘em off the front of the telescope and let the coyotes get ‘em.”

  • Subject: 2.5m Day Log 20070705
  • From: Dan Long
  • Submitted: Thu, 5 Jul 15:59:17 -0600
  • Summer Shutdown:
  • ================
  • The telescope was disassembled to the point of pulling the primary (wind baffle off, M2 off, M2 truss off, wind baffle counterweights reconfigured to balance the telescope, primary light baffle and common corrector off).  The primary comes out tomorrow.                               Cheers,  Dan

The primary is the 2.5 meter work mirror.  It weighs one ton and has been polished to 100 nanometers, that is, no roughness higher than 0.0000039 inches.  That smoothness makes it uncanny– you can’t tell what’s real and what’s reflection – and because the mirror curves, the reflection is in slightly the wrong place.  Dan, who’s in training to be the crew chief, says “mirrors mess with your mind.”  Divested of trusses and baffles, the mirror rests on its back, nested in its cell, looking up. French, the crew chief, crawls under it and stands up through the hole in its center, up to his shoulders in mirror which, just breathing, he’s steamed up. “I’ve never seen this mirror so dusty,” he says.  The dust has to be removed by specialists in Tucson.  The least damage to that mirror, and the crew is out of work until it’s repaired, for months.  Diana, one of the crew, says to French, “You nervous?”  “Any time you’re over the mirror,” says another crew member, “is prayer time.”  They’ll need to lift it out of its cell, then move it to a triangle stand that French designed that looks like tinkertoys with padded stools at each corner.  Meanwhile, they attach a hard cover plate over the mirror, plate rim to mirror rim. The next morning, French says, “Now. Let’s go pull a mirror.”

The crew sets up the triangle stand, figuring it out as they go, asking each others’ opinions, alert, on the jump. Diana can’t account for an allen wrench – tools need to be accounted for in case, in spite of the hard cover, they end up on the mirror – and makes everybody search their pockets.  French gives them explicit directions:  we’ll pick up the mirror by the loop on its hard cover with a hook, attach a dynamometer to the hook, lift the whole thing out slowly; four people will be on ladders over the mirror, watching the numbers on the dynamometer like hawks, making sure it doesn’t get hung up.

The dynamometer is new to them, and they cluster around it, figuring out how the meter works, what the units are.  French has the controls for the lift: “I’m the only guy who can say ‘up,’ but anybody can say ‘stop.’” One of the crew is Chinese; his English is good but not perfect.  “How do you say ‘stop’ in Chinese?” French asks.  The guy tenses his whole body and yells, “chiiiiing.”  They empty their pockets and ask French more questions.  Diana says to the guys climbing the ladders to their watching points over the mirror, “Anything in your pockets?”

The dynamometer with its hook underneath moves over the mirror.  The crew up on the ladders are hunched over.  The hook latches to the loop on the hard cover.  “Ok,” says French, “Up we go,” and presses the controls, and a loud groaning starts then stops immediately.  “Ok,” he says, “the other up.” It’s a physicist joke:  up is down to the minus one, so down is just the other up.  French has a BA in physics which took him 20 years to get.

Dan reads out the numbers on the dynamometer: “2300,” he says; the mirror in its housing weighs 2300 pounds, so the dynamometer is carrying the full weight.  The guys on the ladders check to see if the mirror is clearing the first set of earthquake bumpers.  “Stop.  Feels like it’s hung up.”  “Ok, start.”  Stop, start.  Clear the first set.  Clear the second set.  Pick up speed — though it still moves almost imperceptibly.

Then the mirror hangs free over its cell.  It’s a flat, honeycombed cylinder of glass; 2.5 meters is small for a telescope but this looks huge.  French says,  “We’re going east.”  For the first time, the crew is absolutely silent; mirrors don’t belong floating in the air.  “Ok, coming down,” says French. The mirror hovers a foot above the padded tops of the stools, then settles down.  “Stop.”  Hook and dynamometer, now reading 0, are removed. It’s been a long day and it’s only 9:30 a.m.

By the next day, French and the crew have taken mirror off the triangle and set it into a padded wooden box on a palette, then covered it with more padding, then screwed a wooden top on the box. They lower the box onto the flatbed of a truck and drop a tarp over the box.  They bungee-cord the tarp to the truck, then fasten the box to the flatbed with wide tapes and chains.  The truck should take about six or seven hours to get to Tucson.  The crew stands around the truck, telling stories.  Another telescope mirror was left on a flatbed in the Arizona heat and it cracked.  Once another truck carrying this mirror lost its brakes on the incline by High Rolls.  The truck should have two escorts, one in front and one in back; the front one warns of upcoming potholes; the back one picks up the glass.

  • Subject: 2.5m Day Log 20070706
  • From: Dan Long
  • Submitted: Fri, 6 Jul
  • Summer Shutdown:
  • ================
  • The primary was removed, and since the truck had arrived and the weather was cooperating, it was put in its crate, ready to go to Tucson.  Cheers,  Dan

It was back within a week.  The astronomers relying on data from the telescope hardly notice the downtime; they have lots of data, so meticulously taken and analyzed that astronomy is being revolutionized.  French’s crew shows up early and puts the shiny mirror back where it belongs.

  • Subject: telescope eng report
  • From: French Leger
  • Submitted: Fri, 13 Jul
  • The Primary Mirror has returned.
  • ================
  • The boys got in last night about 7:30 pm. We will remove it from its  crate today as soon as the humidity and weather permits.  Cheers, French


For more about the crew and the survey: my book.

Photo credits, in order:

a bigger, parabolic telescope mirror: with kind permission from Enrico Pinna

2.5m primary mirror still on telescope + French, Dan: Astrophysical Research Consortium, Apache Point Observatory

honeycombed back of another mirror at Apache Point: with kind permission from Ellarien

crew hand:  Astrophysical Research Consortium, Apache Point Observatory

Share Button

8 thoughts on “Pulling the Primary

  1. Oh heck, this is a James Ellroy novel, circa American Tabloid! And it dragged me back into your book, which I’m going to have to reread as soon as I’m done with James M Cain.

  2. And now I’m going to have to go look up James Ellroy and American Tabloid. Why don’t I know anything?

  3. You know many more things than I do, Ann. They’re just not the same things. Don’t bother about Ellroy, unless you’re into seriously vicious political thrillers with two word paragraphs … Bit like that universe really.

  4. Ann, I loved this story. The personality of an observatory does not come from the astronomers who work there, but from the observatory staff: the mountain superintendent, the instrument mechanic, the cook, the driver, and the janitor. They are always an talented group of people and very individualistic. Rem Stone at Lick Observatory was a Marine pilot in the Korean War, and then studied zen archery. Tony Misch is an excellent woodcut artist, and has used the 36″ refractor at Lick to see the drawings he has made of Mars look like the ones of 150 years ago. The whole staff at CTIO worked together as a team and would play jokes on themselves and the astronomers. At Las Campanas, Hector made the greatest empanadas, and also helped to change the instruments on the short shift. Juan Carasco at Palomar was a true Texano and gentleman – he would tell people that his family had lived in 3 different countries without ever moving. Gene Harlan at Lick was a descendant of the Harlan family who were the first to settle the Big Sur coast, and still live there. He knew the name of every flower, tree, bush, star, and told Californiano stories that if perhaps were slightly embellished, where none the less fascinating and could entertain us for hours on a cloudy Lick night. One thing in common with all of them – if something was not working, they would work until they got it fixed, even if it meant not getting any sleep. And if the astronomer got sick, they would often do the observations.

  5. Ok, Nick, now we have to write a book. Maybe just an article. Those are wonderful stories and you don’t hear them just every day.

  6. Beautifully told, Ann. Thank you so much. From 2000 to 2005, I worked alongside Dan, French and the other wonderful people at Apache Point as an SDSS Observer. In trying to get back in touch with French, I found your story. I on of the guys pulling primaries in the summers and your account of the calm and confident processes we all worked on the telesceopes – at French’s ever-grinning command – took me right back there. So thank you.

  7. So you were ordinarily one of the night guys who worked days during the summer shutdown, right? I loved it up at Apache Point — I hear a lot of people do.

Comments are closed.

Categorized in: Ann, Technology, The Cosmos

Tags: , , ,