Astronomy with Lasers, Part II – or Canadians in Scotland

When I did the first part of this post, I said that if Keck were shooting lasers into the sky again I would try to get another night time image, but using the tripod. I did try again the following night but we were quite busy so I didn’t get the chance to get out until late. But good news, the laser was still firing, so I set up the camera on the tripod and went outside. I set the camera up and pointed roughly in the right direction (it was dark out there, you can see anything through the camera’s eyepiece!). I set the camera to its bulb setting and f/8 aperture, manual focus set to infinity and I was ready. I looked up and… no laser! WHAT? They’d switched it off! It was bloody freezing as well.

[I’m sorry, I have to tell this because as I write that phrase – “bloody freezing!” – it reminds me of a story. I studied for my PhD in Edinburgh and one of my fellow students was a Canadian named Steve Torchinsky. For obvious reasons I called him “The Torch”. He told me a story that has stuck with me, about when he was in an Edinburgh pub and a happy but drunken Scotsman started talking to him for no other reason than he was there (it happens). Then he found out The Torch was from Canada and exclaimed the following. Now you must understand, this is only very funny if you say the following in a drunken Scottish accent, otherwise it’s just merely amusing. The drunken Scotsman said, “Don’t talk to me aboot Kanada, Eye’ve bin to Kanada. It’s bloody freeezin‘ in Kanada. It’s so kold in Kanada, the snot FRO-OZE up me NO-OZE!” I love Scotland, and I love the Scottish people… especially the drunken ones. And yes, it is cold in Kanada.]

I got luckier the next day, but I kept one eye on the Keck while I set up the camera and tripod. The following was the result after a 3 minute bulb exposure at f/8.

Keck Laser

As I turned around to go back into the building I noticed that rising over in the East was the Southern Cross. So I set the camera up and exposed it for a minute. I was quite happy with the result, composed with the entrance to the JCMT.

Southern Cross

Astronomy with lasers

As I said in the last post, I’m on the mountain for the next week or so. I’m just working the last quarter of the night for the next few nights, commissioning a new instrument at the JCMT. So I made my way up to the summit leaving the Hale Pohaku Hotel & Resort for Stray Astronomers at about 1:30am. The sky was beautiful and clear – it is one of the natural wonders of the world, truly amazing and I never, ever get used to seeing the night sky from the summit. However, when I looked over at the ridge above us where the biggies are (Subaru and the two Kecks) I noticed this bright orange line shooting out of the Keck I dome into the sky. No, not James Bond, but adaptive optics with lasers.

The technology is actually quite cool. At Keck they call it LGS – laser guide stars. Of course adaptive optics with natural guide stars (NGS) has been around for a while, but it depends on the presence of stars near where you want to observe (within about 30 arcsecs or so). Despite there being “billions and billions” of stars in our Galaxy, apparently this leaves something like 99% of the sky unviewable with adaptive optics. Hence the genesis of this new technology. The laser is shot up in the direction of the astronomical object of interest where it interacts with the sodium layer high up (about 90km) in our atmosphere. The sodium atoms (which got to be there by virtue of meteor strikes, etc, by the way) are excited into emission by the laser and the telescope uses it as an artificial source to correct the aberrations that are introduced by the atmosphere.

All pretty cool and it looks cool as well. I happened to have my camera with me (!) and so went to the back of the JCMT, onto the gantry and set up a long exposure on a tripod. This is what I got:

_mg_5453_ijfr1 _mg_5454_ijfr Not that great, but cool nonetheless. If you look closely (click on the images) you’ll see double stars and two lines for the laser. That’s because the way that the JCMT telescope is built, the whole building rotates when we follow sources around the sky. So the double stars and laser tracks are because the telescope moved in the middle of my exposures. (We’re not going to stop working just because I want to take a photograph!). These were a 1.5 and 3 minute exposures, respectively.

If the lasers are out again in the next couple of nights I’ll set up the tripod outside and see if I can capture a better shot. In the meantime, here’s a really nice image from the Keck website.

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