Observing using the Coudé Feed Telescope

I have now had 3 runs on this telescope, it is very cool and actually quite easy to use (especially to hear other people discuss the telescopes they use!)

To start out my night, I have to open up the shed to expose the telescope mirror (mind you this is an unusual design).

     

One uncool thing about this design is that it is susceptible to wind (more so than other telescopes) so once the wind gets to about 30 mph, the main mirror is shaking around so much that I can't get good data. There are occasions that arise when the wind is so strong that I have to shut down my telescope and therefore go out on the roof in this raging windstorm :(

Once I get the telescope ready, then I have to go take all the covers off of the rest of the light path (see the telescope page) and also fill my CCD's liquid nitrogen dewar (which is always fun)
(see the telescope page for a description of this)

Here is my control room (where I spend many, many hours)
There's actually a pretty nice little stereo in there so that's cool and there is an ethernet connection which is a lifesaver because the telescope control computers are really quite old and slow. Laptops are quite nice :)

Now is when I can start the CCD "zeros" - these are exposures ZERO seconds long - they basically tell me how much "noise" the CCD generates on it's own - this is actually the reason the CCD chip is cooled by liquid nitrogen - the warmer it is, the more noise it generates (pic soon).
After 20 zeros, then I turn on an incandescent lamp (it's quartz) to do 10 "flats" - these are exposures of 5 seconds each to tell me how the CCD is going to react to different colors of the rainbow - generally, CCDs are more sensitive to light that is bluer and it shows in the spectrum (pic soon).
Then the quartz lamp is turned off and I turn on the comparison spectrum lamp. It is lamp with argon gas in it (argon has MANY spectral lines) - I use this to calibrate my wavelengths as what good is it for me to THINK I'm looking at orange light when really I'm looking at yellow - things just won't make sense! So I have to carefully calibrate. During the night, I will take spectra of the comparison lamp every 2 hours or so.
All of these things are important for making the data all pretty in the end.

Once all the preliminaries (zeros, flats, comp) are done, then I can start looking at stars!!

First, I must chose my star!
I have a long list of targets and I must pick and chose amongst them - I have to take into account the brightness (the dimmer the star, the longer I have to look at it), the location in the sky, what time it is (as the Earth rotates, the stars will rise and set), how many I have to get done...
Once I pick my target (the list on the right), then I write it down on the observing log sheet (the list on the left), recording the exposure number, the star name, the brightness, and how long the exposure is going to be (the length is up to my judgment!).
I then go to the computer and pick the star from a list (a cache) of coordinates that is already on the computer - I can enter in new stuff, but that's inefficient. So I push a button to tell the telescope where to point
The computer list: I can set one star in advance.
The window on the right is the cache list and the window on the left is where the coordinates of the star I've picked from the cache get displayed and where I actually push the button to tell the telescope to go to those coordinates.
The telescope points to the star and I can see it with the guider camera (the gain of which must be adjusted according to the star brightness) and I must adjust the star's location (as the telescope gets close, but rarely bang-on):
The TV screen on the left is the actual guider camera - it keeps the star within a box in the middle of the screen. The TV screen on the right has all the data for what time it is and where the telescope is actually pointed and stuff. The silver and black box in the lower right controls the gain of the camera (adjusts star brightness so the machine can guide better). The little black box with red buttons in the lower left is the position adjuster.
I can actually observe now! I go over to the other computer and here is the screen:


This computer runs on a UNIX platform, it is not a Windows computer!! The Windows operating system is just too uncool for scientific operation!
In the red-arrowed window, I type "object" and I get something that asks me how many exposures (1 usually), the exposure time in seconds and the name of the star. I push Enter and then just wait for the exposure to end. In the meanwhile, I'll pick out the next few stars, get the next star's coordinates ready, and just try to plan ahead as best I can.
Once the exposure is done, in the yellow-arrowed window, I type "implot a0001" or whatever the exposure's name is. This brings up a window that has a picture of the spectrum of the star (the blue arrow). I look at this to determine if I have a good enough spectrum (almost always yes) and then I can move on to the next star!
The package we use to see the spectrum picture is called IRAF and it's a special astronomy package.

I do this MANY times a night - I have to keep track of the time so I do my comparisons every 2 hours and sometimes I have stars that I have to look at a few times a night so I have to make sure to look at them before they set.

I keep observing til I run out of stars (rare) or run into daylight. Then I just close everything down.
Things I have to be aware of/watch out for:
- I can't let stars get too close to the horizon - they're harder to see (i.e. longer exposures)
- wind can be a problem (as I mentioned above)
- cirrus clouds can be observed through, but they lengthen exposure time
- other people on the mountain can make us all shut our telescopes down if the weather is unfavorable or dangerous to the telescopes - they will broadcast a message that all the computers on the mountain display or they can call everyone.
--- very high humidity (more than 90%) can cause water to condense onto the mirrors and that is bad
--- high winds can put lots of strain on the domes and on the telescope motors and stuff
--- lightning is obviously quite dangerous
--- too many clouds to make observing worthwhile (this is quite subjective and can cause great debate)

Back to the November 2005 observing diary
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