| The Worky Bit |
[Sep. 4th, 2008|08:36 pm] |
Hey all,
I'll do a bit of a post about the worky bit of the trip just to pretend that this wasn't all about the opportunity to see the BigHeads on Easter Island.
The telescope is located on a mountain, Cerro Pachon, at 9000ft, which means it's above most of the clouds. Unfortunately it wasn't quite above *all* of the clouds and so two thirds of the intended science objectives died when I saw this:
A decent chunk of astronomy deals with accurately figuring out how bright things are and it's impossible to do if clouds keep flitting across your image, obscuring that light astronomers so desperately crave. However, we had a few backup projects in case of clouds so all was not lost. There was a reasonable amount of snow up there but a dedicated plow had shoved it out of my way. Oh, that little Toyota in the photo was the car I used for the 4 days I was up there. The 'hotel' was 3km from the dining room and telescope so I had great fun zipping along the dirt track. Of course, the car had a top speed of about 45km/h and the brakes weren't so good.
I spent a bit of time wandering around in awe of the magnificent vista then figured I should actually figure out the night's observing plan, given the cloud condition. Luckily, my room had wireless so I listened to songs through youtube (it has *everything*) and worked out a rough strategy then headed up to the telescope to do some calibration images. Since the telescope and camera are not perfectly clean, you can end up with artifacts on your images, primarily caused by bits of dust on various bits of the system, e.g. filters, mirrors etc. So to get rid of those, you take an image of a plain white screen. Then any variations in your image (anything that isn't a white screen) is due to dust etc. in the system. Then you divide those out of your science images. Anyway. That didn't take too long so I went over the weather forecast with the telescope operators (they move the telescope for you and do the engineery-stuff) and it was not good. A giant band of cloud from the south was headed our way. In fact, here is a picture of it from earlier in the day:
We went off to eat dinner and collect our night lunches. A night lunch is intended to replace the meal that you usually eat around the middle of your waking hours. It's pretty much the same as a regular lunch except you eat it at about midnight. Or, if you're like me - the child at the cinema who had eaten all of her sweeties before the trailers were finished - you eat it at about 9pm. Earlier if you're bored. We came back to the telescope and started setting up. The sky was cloudy but sometimes if the clouds are thin you can observe anyway, as long as you're not aiming for good information about the brightness of an object. So we pointed a third magnitude star which means, in clear weather, it is easily visible to the naked eye. The telescope could barely 'see' it. This is a 4m telescope, meaning the diameter of the mirror is about twice the length of Jeremy Clarkson. We clearly had a problem with the weather. The objects I was aiming to observe were about 40 million times fainter than that. So the night was dead. We hung out until 3:30am when I was told that all the other observers had given up hours ago (pansies). We headed back down to our rooms about an hour before twilight, which signals the end of the night for astronomers.
I slept from 5am til 12pm - this is a fairly early night for an astronomer. I woke up hoping it would look better but no. It looked worse than yesterday, if anything. Here's a picture of the dome that houses the telescope I was using. Note the giant giant band of cloud.
Regardless, I went through the motions of setting up and taking calibration frames. Dinner, nightlunch, and a closed dome. Darn. Luckily for me, my older brother was trying to work in Australia, 14 time zones ahead, and I bugged him via skype. We had great fun being the grown-ups we are by using an online application designed to allow people to hold online business meetings. What they didn't realize was just how much fun two people in their mid-twenties could have with the drawing feature they had added. The result is below. We sent it to our mum so she can put it on the fridge. I expect to see that at Christmas, Mum.
At 3:30am the encouraging news that there appeared to be a hole in the southern edge of the cloud. I had a quick look through my object list and, yes, there was one lump of rock in that region. So we waited 30 minutes to check that the hole and weather was roughly stable and... in the time the wind picked up to 80km/h meaning that the dome couldn't be opened even if the sky was perfectly clear. So there went that night.
Just for fun, here's a pic from the telescope controls:
Rinse and repeat. Slept 6am-1pm. Lunch, take photos, calibration images, dinner, nightlunch. Watch all-sky camera show nothing but clouds for 5 hours. And then the temperature dropped and ice began to form. Once the dome had ice on it, that was it. Game over. You can't open an icy dome for fear the ice will drop inside onto the telescope mirror. I should say that a telescope mirror is not like a mirror one might have at home, which has the shiny bit protected by a layer of glass. This layer of glass produces all sorts of optical distortions and problems which you don't notice too much when checking your hair (as I do frequently) but these distortions have a terrible effect on the quality of astronomical images. So we just have the shiny bit, typically made of an aluminIum alloy, with no protective layer. The thickness of aluminIum layer is only about 0.1% of the thickness of a hair on your head. So you can imagine that the layer is pretty fragile and needs to be protected from falling ice, dust-laden winds, spitballs, etc.
More importantly for our safety, ice had begun to form on the winding roads that led back to our warm beds. Fog had also rolled in. So we packed up and set off in a procession - one telescope operator (TO) leading, me in the middle in my little Toyota, followed by the other TO. I'd like to point out that they had big trucks with proper manual gearboxes and my stupid car was an automatic which had a nasty habit of wanting to stay at 40km/h - not a good speed on steep, bumpy, icy roads and one wrong turn will see you sliding over the edge of a cliff. But we made it just fine and headed for bed. I set the alarm for 5:30am to catch the sunrise but one look out the window was sufficient to confirm that the fog had not lifted and waking up that early was pointless. So back to bed I went.
I headed back to La Serena at 3pm with no data to show for 3 nights. That's the danger of being an observational astronomer. Sometimes you win, sometimes you watch youtube for 3 nights. I mean, err, sometimes you write scientific papers and proposals for three nights. Yeah.
And now the backpacking fun begins! More from La Serena coming soon...
Rach |
|
|
![[info]](http://l-stat.livejournal.com/img/userinfo.gif){kind=small}
rach150384's journal
