AY 105 Lab Experiment #6: CCD Characteristics II: TheRevengeIn this lab, you’ll continue investigating the properties of CCDs that you startedin Experiment #2. You’ll measure CCD characteristics and amplifier properties suchas the read noise (e−), gain (e−/ADU), and dark current.Startup. The CCD detector used in this lab is cooled by a thermoelectric cooler(TEC), which takes about 5 minutes to cool the CCD to a stable equilibrium. Thusthe first thing you should do is to start up the CCD software and make sure the CCDis cooling.On the PC, start the“pictor” program. The program will start and display somemenu items at the top.Check to see that the Pictor camera itself has the power cable connected, and thatthe transformer is plugged in. You should see some digits displayed on the LEDs onthe back of the camera. To initialize the camera operation, pull down the Connectionmenu and select Connect. If the menu only displays Disconnect, choose that, then pulldown the menu again and select connect. You should see a message saying that it istalking to the camera; if not, check the serial cable connection (the thin black cablewith an RJ connector on the end) between the PC and the CCD camera and try again.Then, set an initial temperature of −10◦C by pulling down the Camera menu andselecting Set Temperature. Enter −10 into the display and make sure the Max Coolingbox is unchecked.At any time, near the bottom right-hand corner of the screen the software displaysa numb er like “−10.22 75 % ”. This is a reading of the CCD temperature in◦C andthe percentage of the total available cooling power that is being applied to the CCD.After you set a new temperature, you’ll see these numbers change a lot, and you maynotice that the approach to the set temperature is underdamped. It oscillates aboutthe set temperature for a while before settling down, and takes about 5 minutes tofully settle.Configuration. CCD detectors are very sensitive to light. To achieve accurateand reproducible results, a change is required in the experimental methods generallyused thus far, where optics and detectors were used in the open. To reduce as much aspossible the stray light reaching the CCD, in this lab the detector is located on top andat the far right end of a (more or less) light-tight enclosure. Look inside at the layoutof the optics inside this “black box”; sketch this in your lab notebook, and ask theinstructor or TA to explain anything about it you don’t understand. You may removethe red screws on the top and lift the handle to reveal the diffuser / filter / test patternlocation inside the enclosure. Check to make sure that the test pattern is in the final1Ay 105 Spring 2008 Experiment 6 2slot (extreme right). Replace the cover and tighten the red screws with your fingers.Also note the configuration of the cables—the serial and power cables to the CCDcamera as described above.You will note that we use a special high-end light source for our setup - a flashlightwith black tape over it and a small hole punched in.Method. In this lab you’ll use the windows PC to initiate CCD exposures from 5seconds to several minutes of integration time, read out the serial CCD data and displayit, and save the “good” exposures in FITS format for analysis during the second labperiod. The exposure time (and some other parameters that are not critical for thislab) can be set by clicking on the icon that resembles four horizontal lines (next to thetext display at the top that normally reads “Default”). As discussed in class #2 thisCCD does not have a shutter, but instead operates in “frame-transfer” mode, takingabout 4 ms to transfer. However, due to a settling time of the bias after the softwareclears the chip, you should not use exposure times shorter than 5 seconds.Exposures are started by clicking on the button at the top of the screen that lookslike a camera. Try it. Subwindows will pop up that display the status of the exposureand the readout, and at the end the image will be displayed on the screen with anautomatic stretch. There are also items in other menus that talk about taking darks,biases, etc. DO NOT use these, as they have the problem of taking exp osures that aretoo short. In addition, you do not want the software to automatically subtract thesecorrection frames from your image, which would make a proper analysis impossible.The program saves each image in an internal temporary file. If you want to save animage for later transfer, click the left mouse button on the image to select it, then pulldown the File / Save menu item. Images saved in FITS format have a “.fts” extension.Also, note that the PC software displays the image such that the amplifier is in theupper left-hand corner, but later when you display the image in IRAF it will be flippedtop to bottom from what the PC shows, placing the amplifier in the lower left-handcorner of the display.Required Exposures.The first exposures you obtain are images of the test target with between 2500and 3000 ADU (“analog-to-digital units”, also called DN, for “digital numbers”) abovethe bias level. Among other things, this will tell you whether everything is workinginside the enclosure. With the lamp off, you can take a (minimum) 5-second exposureto determine roughly the bias level. Before you obtain your final frame, you may needto take some short exposures to adjust the focus of the Nikon camera lens. You canaccess the lens by removing the four red screws on the front cover; rotate the lens onlya small amount from its original position (shouldn’t be far off, depending on how wellthe previous group did). Replace the cover each time before taking another exposure.Once you have an exposure time that gives you the proper signal level, take another atAy 105 Spring 2008 Experiment 6 31/5 of this exposure time, and a third at 1/25 of this. These data will be used duringthe data analysis phase to see how linear the response of the CCD detector is (i.e.,counts in DN should be a perfectly linear function of exposure time in seconds).Next take several 5-second dark exposures (with the lamp off), which we will useas our bias frames. Then, take two dark exposures at each of the exposure times usedfor the test target–these will make up your dark exposures.Now remove the test pattern from inside the enclosure, turn on the lamp, andtake several well-exposed “flat field” exposures using just the opal glass diffuser. Usethe