Your spectra will be placed in your FTP area as they are taken, in a separate directory for each night. For example, your spectra taken on 2006 Sept. 15 UT with the 32-inch telescope will be stored in directory /060915_32in/images, along with any other exposures which may have been taken for you on the same night.
Your spectrum exposures will be named AAAnnnnn.fit, where AAA is your 3-character user ID and nnnnn is a 5 digit number. For each spectrum exposure, you will also find a companion data file AAAnnnnn_TrackingData.txt. This text file contains data about how accurately the spectrograph's tip-tilt mirror system has kept the target object centered on the optical fiber being used to take the spectrum, and also about how the flux from the target object varied during the spectrum exposure. An example tracking data file is shown below:
Date UT xError yError %TiltX %TiltY Box count 2006-04-16 07:12:49 -0.0 0.5 50.45 53.31 68144 2006-04-16 07:12:56 -0.4 -0.9 50.01 51.67 67843 2006-04-16 07:13:03 -0.0 0.1 50.01 51.89 70239 2006-04-16 07:13:08 -0.0 -0.2 49.99 51.50 68152 2006-04-16 07:13:12 -0.3 -0.5 49.69 50.67 67310 2006-04-16 07:13:18 0.4 0.0 49.69 51.40 65068 2006-04-16 07:13:25 -0.1 0.9 49.62 52.97 65906 ... 2006-04-16 07:32:50 0.7 0.0 35.26 76.31 70277 2006-04-16 07:32:55 -0.2 0.2 35.12 76.61 70448 2006-04-16 07:32:59 0.6 0.0 34.36 76.61 69515 RMS tracking error: 0.71 pixels Average track box count: 69409 Note: * = Tracking restarted after nudging the telescope. |
In the above table, xError and yError are the tracking errors (offsets of the image of the target object from the optical fiber) in pixels (each pixel here corresponds to about 0.5 arcsecond), %TiltX and %TiltY are the tilts of the tip-tilt mirror in the x and y directions, expressed as a percentage (50% means the mirror's home position, and 0% and 100% represent the mirror's extreme positions), and Box count is a measure of the flux from the target object (this flux would drop if a cloud passes in front of the target during the spectrum exposure; a nearly constant flux would indicate stable observing conditions). When one of the mirror tilts gets too close to 0% or to 100%, the telescope is nudged by a very small distance to re-center the target on the optical fiber, after which the tip-tilt mirror system resumes its work; such events are marked by an asterisk (*) in the appropriate line of the tracking data file. Note that the shutter remains open during the telescope nudging and tracking restart process. The RMS tracking error and the average track box count during the spectrum exposure are given at the end of the tracking data file.
When spectra are taken for you on a given night, the directory corresponding to that night (in the above example, that would be /060915_32in) will contain the following subdirectories:
These directories store bias and dark frames taken with the spectrograph's camera in the evening, before the start of the nighttime observations. Master bias and dark frames are obtained by median combining three individual bias and dark frames, respectively. The dark frames have an exposure time of 150 seconds; you are supposed to scale the master dark frames when using them to calibrate spectrum exposures whose exposure times are not equal to 150 seconds.
We store both the individual calibration files taken in the evening and the master calibration files which are produced by median combining the individual calibration files. You will probably wish to use these master files for your calibrations; the individual calibration files are provided in case you wish to prepare your own master calibration files by combining the individual calibration files.
Our naming convention for spectrograph master bias and dark frames is MasterNAME_binN_spectrograph.fit, where NAME is either Dark or Bias, and N is either 1 or 2. Some examples:
| MasterDark_bin1_spectrograph.fit | Master unbinned spectrograph dark frame (1024 x 1024 pixels). |
| MasterBias_bin2_spectrograph.fit | Master 2x2 binned spectrograph bias frame (512 x 512 pixels). |
The names of individual calibration files follow these conventions:
Dark_binN_nnnn_spectrograph.fit
Bias_binN_nnnn_spectrograph.fit
where N is 1 or 2 and nnnn is a 4-digit number.
On rare occasions, technical problems prevent us from obtaining a full set of spectrograph calibration files. If this happens on a night when we have obtained spectra for you, you will notice that either the /Spectrograph-Bias and/or /Spectrograph-Dark subdirectories will not have been created, or they will not contain all the spectrograph calibration files you need. In these cases, you should search the directories which store the images from the past few nights, where you may find the spectrograph calibration files you need. If you can't find recent spectrograph calibration files on your FTP area (which will happen if you haven't taken any spectra over the last 10 days), please contact us, and we will place suitable recent calibration files on your FTP area. Unless there has been a change of camera or a change in camera temperature, spectrograph calibration frames from a previous night will be virtually identical to those taken on the current night.
The directory corresponding to any given night is kept on the FTP server for 10 days, and is then moved to another computer for back-up storage. If you need to download data which is more than 10 days old, please contact us, so we can temporarily restore it to the FTP Server.
If some of your spectra are seriously affected by clouds or other problems, please send us an e-mail mentioning the UT date when the spectra were taken and the file names of the affected spectra, so we may provide a refund.
|
If you have questions about the the observation request format or about the above processes please e-mail them to mbs@tenagraobservatories. |
[What's New?] [Telescope Overview and Service] [Who Are We?] [Telescope Sites] [Supernovae Discoveries] [Feedback] [Web Site Search] [Links] [Contact Us]