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1. sliced transmitted unchanged or masked by the slits The slits are not normally used for observations unless the star is very bright R 120000 can be reached with the narrow sit Table 2 Basie observing modes Mode Slicer Binning KV speed Normal Slicer 3x1 fast Fiber _ Fiber 4x4 slow 2 How to use CHIRON 2 1 CCD parameters The CCD detector is a e2v device with 4096 H x4112 V square pixels of 15 micron size with graded coating It lives in a dewar cooled by liquid nitrogen with the Monsoon Orange controller Left and right parts of the detector are read with different amplifiers The gain and readout noise in fast and slow readout modes are listed in Table 3 Table 3 Readout modes of the CCD Mode Readout Upperle Upperrighi time RON Gain RON Gain s el ayADU a a ADU Nom bd a5 239 17 205 Normal 2x2 14 43 41 192 Fast Ixl 22 96 TA 219 Fast 2x2 10 75 61 220 The detector response is slightly non linear A formula to linearize the measured signal 5 in ADU Score 8 1 5 leads to the resulting linearity of about 1 at signal level up to 10 ADU using the non linearity coefficients k of 4 5 40 x 1075 in the normal mode and 5 0 4 3 x 1078 in the fast mode for the left right amplifiers It is not recommended to exceed the signal level of 10000 counts Echelle dispersion is directed along the columns vertically cross dispersion along the lines Th2. 6443 3 124 4528 5 4546 8 4565 2 89 6209 3 6334 9 6370 5 125 4492 4 4510 5 4528 5 90 6229 7 6264 5 6299 3 126 4456 9 4474 7 4492 4 91 6161 6 6195 7 6229 7 127 4421 9 4439 4 4456 9 92 6095 0 6128 3 6161 6 128 4387 5 4404 7 4421 9 93 6029 8 6062 4 6095 0 129 4353 7 4370 6 4387 5 94 5966 0 5997 9 6029 8 130 4320 3 4337 0 4353 7 95 5903 6 5934 8 5966 0 191 4287 4 4303 9 4920 3 96 5842 4 5873 0 5903 6 132 4255 1 4271 3 4287 4 97 5782 8 5812 4 5842 4 133 4223 2 4239 1 4255 1 98 5723 8 5753 1 8782 5134 4191 8 4207 5 4223 2 99 5666 3 5695 0 5723 8135 4160 9 4176 3 4191 8 100 5609 9 5638 1 5666 3 136 4190 4 4145 6 4160 9
3. Cerro Tololo Inter American Observatory CHIRON manual mp PO i li lana A Tokovinin Version 2 May 25 2011 manual pd 1 Overview inthe cous room Viewer 4 Image slicer Ss Figure 1 Light path in CHIRON from the telescope to the CCD Elements under user control are pink colored CHIRON is a high resolution fiber fed echelle spectrometer installed at the CTIO 1 6 m telescope It can record multi order echelle spectra of single objects stars with spectral resolution up to A 80000 3 pixels per resolution element The spectral format on the detector is fixed covering the wavelength range from 4200 to 8800A without gapa TBC Figure 1 shows main elements of CHIRON from the user perspective We follow the path of starlight directed towards the fiber module FEM by a diagonal mirror located in the telescope GAM at certain position of the pickup arm The star image is focused on a mirror with a hole most of the light goes into the fiber the remaining halo is reflected towards the acquisition guiding camera A small prism can be placed behind the mirror to feed calibration light quarta or Th Ar lamps to the spectrometer The spectrometer is located in the code room The light beam emerging from the fiber can be ro shaped into a slit like image by the image slicer to increase spectral resolution without ligt loss The slicer can be moved out of the way to work with bare fiber image with
4. The effect is immediate In Fig 4 the integration time is 100 ms Using hand paddle move the telescope to bring the star into the bax Most of the image disappears in the hole and we see a ring donut as shown in Fig 4 The guiding loop can now be closed To view the image better adjust the display using its control panel display menu Options gt Control panel It is helpful to adjust the contrast and brightness and to use zoom for a larger view of star image in the hole For focusing the telescope move the star away from the hole make sure that the image is not satu rated in the camera max count lt 4096 and in the display With bad settings of brightness contrast the central part of the image looks flat with right settings it is peaked The position of the guider arm must be checked because the GAM control software systematically goes wrong so the displayed coordinates of the guide arm do not match its actual position The correct position should be X 268 Y 259 Z 41 Put a bright star away from the hole defocus the telescope and verify that the image is donut like not cut on one side If this is not the case re initialize the GAM control program 2 4 Spectral format The spectral formal is fixed It covers the wavelength range from 410nm start of the bluest order 137 to 874hm end of the reddest order 65 Figure 5 shows the spectrum of a FONI star Canopus with order numbers and approximat
5. e charge transfer efficiency is very good about 0 999986 per pixel in the line direction and even better in the column direction The CCD has minor cosmetic defects In the left amplifier there is a charge trap at X 566 567 and Y 3414 pixel count in the trimmed image making for two bad columns In the right half the most prominent defect is a charge trap at X 2305 2306 and Y 2460 which leaves a dark tail in those two columns below the trap The tail extends for about 1000 pixels then disappears There are two localized detector blemishes at X Y 2347 2526 and 2399 2516 22 Exposure time calculator Calculation of the sigmal to noise ratio per pixel is based on the following formula SIN Na VN RE OJ where Nps is the number of stelar photons per spectral pixel collected during the exposure time A is the CCD readout noise in electrons K is the numberof binned pixels across the order In the normal mode R 8 K 9 pixel size is 0 02024 In the fiber mode with 4x4 binning and slow readout R 43 K 25 and the spectral pixel is 4 times larger The number of photons received during exposure time tis calculated as Nou Poet 10794 el pixel 6 where Fy 3 4E5 photons s pixelis the fax of V 0 star outside atmosphere per 0 0202A 0 04 is the total system efficiency V is source magnitude These parameters are valid around 500 nm near the center of order in the normal mode The plots in Fig 3 were produced using
6. e central wavelengths The order table is listed in the Appendix Note that the order 109 517 nm is right at the center it is split between two amplifiers 2 5 Taking spectra CHIRON and its CCD are controlled by the ctice1 computer Use VNC connection to 139 229 12 29 9 Read the GUI user manual to find out how to operate it The program controls all CHIRON motors prism slicer iodine cell and focus calibration lamps and CCD The nominal best focus setting la 1024 TBC Ship few clio ac edu atokovin ochlle CHIGOS 12 chiron User Manual pdf ob so 100 tho E io Figure 5 Spectral format of CHIRON covering the range 410 874nm Spectrum of Canopus FOI in normal mode is displayed in the background bias subtracted and trimmed 4096x4112 pixels Order numbers are indicated by the scales above and below some stellar lines in green approximate central wavelengths of the orders in red The vertical green line indicates the division between upper left and lower right amplifers Figure 6 Spectrum of the Th Ar comparison lamp 2 6 Checklist Open the telescope and place the GAM arm at X 268 Y 259 e Switch on the FEM electronics on the telescope e Enter CHIRON GUI verify that it is connected to the CCD controller temperature monitor and TSC green colored boxes Take ThAr spectrum Check temperatures of the CCD and CHIRON Give right values e Enter the PCGuider program verify that it acquires the gu
7. ide camera images 2 7 Troubleshooting To be written Cite software troubleshooting by Marco A Order table Order numbers N are listed below with wavelength limits min max corresponding to the free spectral range and central wavelengths These wavelengths are approximate N Mino Cent Max N Min Cent Max 65 8607 5 8673 9 8740 4101 5554 6 5582 2 5609 9 66 8477 8 8542 5 8607 2102 5500 4 5527 5 5554 6 67 8352 2 8415 0 8477 8 103 5447 3 5473 8 5500 4 68 8230 3 8291 3 8352 2104 5395 2 5421 2 5447 3 69 8111 9 8171 1 6230 3 105 5344 0 5369 6 5395 2 70 7996 8 8054 4 8111 9106 5203 8 5318 9 5344 0 TI 7885 0 7940 9 7996 9 107 5244 6 5269 2 5293 8 72 1776 3 7830 6 7885 0 108 5196 3 5220 4 5244 6 73 7670 8 7723 4 7776 3 109 5148 8 5172 5 5196 3 TA 7567 8 7619 0 7670 5 110 5102 2 6125 5 5148 8 75 7467 3 7517 4 7567 5 111 5056 5 5079 3 5102 2 76 7369 7 7418 8 7467 3 112 5011 5 5034 0 5056 5 TT 1274 6 7322 2 7369 7 113 4967 4 4989 4 5011 5 78 7182 0 7228 3 7274 6 114 4924 0 4945 7 4967 4 79 7091 6 7136 8 7182 0 115 4881 3 4902 7 4924 0 80 7003 8 7047 6 7091 6 116 4839 5 4860 4 4981 4 81 6917 6 6960 6 7003 5 117 4798 3 4818 9 4839 5 82 6893 8 6875 7 6917 6 118 4757 8 478 0 4798 3 83 6751 9 6792 8 6833 8 119 4718 0 4737 9 4787 8 84 6672 0 6712 0 6751 9 120 4678 8 4698 4 4718 0 85 6594 0 6633 0 6672 0 121 4640 3 4659 6 4678 8 86 6517 8 6555 9 6594 0 122 4602 4 4621 4 4640 3 87 6443 3 6480 5 6517 8123 4565 2 4583 8 4602 4 88 6370 5 6406 9
8. spectral resolution decreased to R 30000 or to mask the fiber by sits increase the resolution at the expense of light loss A viewer with manually activated mirror is used only for troubleshooting to see the sliced image Other user controlled elements are the shutter iodine cell which can be placed in or out of the beam and the focusing stage The CCD is operated by a GUI driven data acquisition program CHIRON is designed to be very stable its internal environment is maintained at constant temper ature Opening the spectrometer any other intervention or manipulation are strictly prohibited To specify observations astronomer needs to decide whether the image slicer is needed whether the Table 1 CHIRON parameters cer Todine cell CCD Slicer R 80000 IN Normal Fast readout Fiber R 30000 OUT Binning HxV Slits wide narrow Region of interest iodine cell should be used and what detector parameters are best suited for the program Although these choices can be made in any combinations only a subset of all combinations makes sense Two observing modes suitable for typical science applications are defined in Table 2 Each program must also specify required calibration data Th Ar and quartz spectra bias frames etc sits Figure 2 Images of the slie as seen through the viewer with fiber illuminated by the quartz lamp The position of the translation stage defines whether the fiber image is
9. these data Figure 3 Estimated signal to noise ratio at 500nm vs exposure time in normal mode with slicer left and in the fiber mode right The numbers near curves indicate V magnitude of the source i mne Se al ETE SN av ae te PA i ee TT ka ee oe pen ee KZ ee CO on NNN nuguuugag en se EN veste NNN se MANON ao muka mnj mem 7 Figure 4 Snapshot of the PCguider screen during guiding 2 3 Acquisition and guiding The guiding camera is connected to the guiding PC ctioxb Use VNC connection to 139 229 12 62 1 In the VNC screen open the PCguider program from a menu activated by the left mouse button Fig 4 In order to see better the star images use automatic intensity scaling To do so use menu in PCguider Options Parameters olut off the default is signa When the field is illuminated by sky or dome light dark images of the two holes are seen The guiding box should be centered on the small hole normally at X 289 Y 255 You may want to shift the box by 1 pixel to achieve better centering of the star in the hole The normal box size is 29 pixels The North South direction coincides with Y After pointing the telescope the object should be seen on the screen Adjust camera integration time to avoid saturation max counts lt 4096 In the PCguider menu use Windows Camera Control Integration Time set the new value press Enter
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