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diff --git a/noao/imred/ccdred/doc/guide.hlp b/noao/imred/ccdred/doc/guide.hlp new file mode 100644 index 00000000..5006a6ec --- /dev/null +++ b/noao/imred/ccdred/doc/guide.hlp @@ -0,0 +1,717 @@ +.help guide Feb88 noao.imred.ccdred +.ce +User's Guide to the CCDRED Package +.sh +1. Introduction + + This guide provides a brief description of the IRAF CCD reduction +package \fBccdred\fR and examples of reducing simple CCD data. It is a +generic guide in that it is not tied to any particular type of data. +There may be more specific guides (or "cookbooks") for your data. +Detailed descriptions of the tasks and features of the package are +provided in the help documentation for the package. + + The purpose of the CCDRED package is to provide tools for the easy +and efficient reduction of CCD images. The standard reduction +operations are replacement of bad columns and lines by interpolation +from neighboring columns and lines, subtraction of a bias level +determined from overscan or prescan columns or lines, subtraction of a +zero level using a zero length exposure calibration image, subtraction +of a dark count calibration image appropriately scaled to the dark time +exposure, division by a scaled flat field calibration image, division +by an iillumination image (derived from a blank sky image), subtraction +of a scaled fringe image (also derived from a blank sky image), and +trimming the image of unwanted lines or columns such as the overscan +strip. Any set of operations may be done simultaneously over a list of +images in a highly efficient manner. The reduction operations are +recorded in the image header and may also be logged on the terminal and +in a log file. + + The package also provides tools for combining multiple exposures +of object and calibration images to improve the statistical accuracy of +the observations and to remove transient bad pixels. The combining +operation scales images of different exposure times, adjusts for +variable sky background, statistically weights the images by their +signal-to-noise, and provides a number of useful algorithms for +detecting and rejecting transient bad pixels. + + Other tasks are provided for listing reduction information about +the images, deriving secondary calibration images (such as sky +corrected flat fields or iillumination correction images), and easily +setting the package parameters for different instruments. + + There are several important features provided by the package to +make the reduction of CCD images convenient; particularly to minimize +record keeping. One of these is the ability to recognize the different +types of CCD images. This ability allows the user to select a certain +class of images to be processed or listed and allows the processing +tasks to identify calibration images and process them differently from +object images. The standard CCD image types are \fIobject\fR, +\fIzero\fR level, \fIdark\fR count, and \fIflat\fR field. For more on +the image types see \fBccdtypes\fR. + + The tasks can also identify the different filters (or other subset +parameter) which require different flat field images. This means you don't +have to separate the images by filter and process each set separately. +This feature is discussed further in \fBsubsets\fR. + + The tasks keep track of the reduction steps completed on each +image and ignore images which have been processed. This feature, +along with recognizing the image types and subsets, makes it possible to +specify all the images to a task with a wildcard template, such as +"*.imh", rather than indicating each image by name. You will find this +extremely important with large sets of observations. + + A fundamental aspect of the package is that the processing +modifies the images. In other words, the reduction operations are +performed directly on the image. This "feature" further simplifies +record keeping, frees the user from having to form unique output image +names, and minimizes the amount of disk space required. There +are two safety features in this process. First, the modifications do +not take effect until the operation is completed on the image. This +allows you to abort the task without messing up the image data and +protects data if the computer crashes. The second feature is that +there is a package parameter which may be set to make a backup of the +input data with a particular prefix such as "orig" or "imdir$". This +backup feature may be used when there is sufficient disk space, when learning +to use the package, or just to be cautious. + + In a similar effort to efficiently manage disk space, when combining +images into a master object or calibration image there is an option to +delete the input images upon completion of the combining operation. +Generally this is desirable when there are many calibration exposures, +such as zero level or flat field images, which are not used after they +are combined into a final calibration image. + + The following sections guide you through the basic use of the +\fBccdred\fR package. Only the important parameters which you might +want to change are described. It is assumed that the support personnel +have created the necessary instrument files (see \fBinstruments\fR) +which will set the default parameters for the data you will be +reducing. If this is not the case you may need to delve more deeply +into the details of the tasks. Information about all the parameters +and how the various tasks operate are given in the help documentation +for the tasks and in additional special help topics. Some useful help +documentation is indicated in the discussion and also in the +\fBReferences\fR section. +.sh +2. Getting Started + + The first step is to load \fBccdred\fR. This is done by loading +the \fBnoao\fR package, followed by the image reduction package +\fBimred\fR, and finally the \fBccdred\fR package. Loading a +package consists of typing its name. Note that some of these packages may be +loaded automatically when you logon to IRAF. + + When you load the \fBccdred\fR package the menu of tasks or commands +is listed. This appears as follows: + +.nf + cl> ccdred + badpiximage ccdtest mkfringecor setinstrument + ccdgroups combine mkillumcor zerocombine + ccdhedit cosmicrays mkillumflat + ccdlist darkcombine mkskycor + ccdproc flatcombine mkskyflat +.fi + +A summary of the tasks and additional help topics is obtained by typing: + + cl> help + +This list and how to get additional help on specific topics is described +in the \fBReferences\fR section at the end of this guide. + + The first command to use is \fBsetinstrument\fR, which sets the package +appropriately for the CCD images to be reduced. The support personnel +should tell you the instrument identification, but if not a list +of known instruments may be listed by using '?' for the instrument name. + +.nf + cl> setinstrument + Instrument ID (type ? for a list) \fI<enter instrument id or ?>\fR + <Set ccdred package parameters using eparam> + <Set ccdproc task parameters using eparam> +.fi + +This task sets the default parameters and then allows you to modify the +package parameters and the processing parameters using the parameter +editor \fBeparam\fR. If you are not familiar with \fBeparam\fR see the +help or CL introduction documentation. For most terminals you move up +and down through the parameters with the terminal arrow keys, you +change the parameters by simply typing the desired value, and you exit +with control Z or control D. Note that you can change parameters for +any task at any time with \fBeparam\fR and you do not have to run +\fBsetinstrument\fR again, even if you logout, until you need to reduce +data from a different instrument. + + The \fBccdred\fR package parameters control general I/O functions of +the tasks in the package. The parameters you might wish to change are +the output pixel type and the verbose option. Except when the input +images are short integers, the noise is significantly greater than one +digital unit, and disk space is critical, it is probably better to +allow the processing to convert the images to real pixel datatype. The +verbose parameter simply prints the information written to the log file +on the terminal. This can be useful when little else is being done and +you are just beginning. However, when doing background processing and +other IRAF reduction tasks it is enough to simply look at the end of +the logfile with the task \fBtail\fR to see the current state of the +processing. + + The \fBccdproc\fR parameters control the CCD processing. There are +many parameters but they all may be conveniently set at this point. +Many of the parameters have default values set appropriately for the +instrument you specified. The images to be processed can be specified +later. What needs to be set are the processing operations that you +want done and the parameters required for each operation. The +processing operations are selected by entering yes or no for each one. +The following items briefly describe each of the possible processing +operations and the additional parameters required. + +.ls \fIfixpix\fR - Fix bad CCD lines and columns? +The bad pixels (cosmetic defects) in the detector are given in a file +specified by the parameter \fIfixfile\fR. This information is used +to replace the pixels by interpolating from the neighboring pixels. +A standard file for your instrument may be set by \fBsetinstrument\fR +or if the word "image" is given then the file is defined in the instrument +data file. For more on the bad pixel file see \fBinstruments\fR. +.le +.ls \fIoverscan\fR - Apply overscan strip correction? +The overscan or prescan region is specified by the parameter +\fIbiassec\fR. This is given as an IRAF image section. Only the +part of the section corresponding to the readout axis is used and +the other part is ignored. The length of the overscan region is +set by the \fItrimsec\fR parameter. The overscan +region is averaged along the readout axis, specified by the parameter +\fIreadaxis\fR, to create a one dimensional bias vector. This bias is +fit by a function to remove cosmic rays and noise. There are a number +of parameters at the end of the parameter list which control the +fitting. The default overscan bias section and fitting parameters for +your instrument should be set by \fBsetinstrument\fR. If the word +"image" is given the overscan bias section is defined in the image +header or the instrument translation file. If an overscan section is +not set you can use \fBimplot\fR to determine the columns or rows for +the bias region and define an overscan image section. If you are +unsure about image sections consult with someone or read the +introductory IRAF documentation. +.le +.ls \fItrim\fR - Trim the image? +The image is trimmed to the image section given by the parameter +\fItrimsec\fR. A default trim section for your instrument should be +set by \fBsetinstrument\fR, however, you may override this default if +desired. If the word "image" is given the data +image section is given in the image header or the instrument +translation file. As with the overscan image section it is +straightforward to specify, but if you are unsure consult someone. +.le +.ls \fIzerocor\fR - Apply zero level correction? +The zero level image to be subtracted is specified by the parameter +\fIzero\fR. If none is given then the calibration image will be sought +in the list of images to be processed. +.le +.ls \fIdarkcor\fR - Apply dark count correction? +The dark count image to be subtracted is specified by the parameter +\fIdark\fR. If none is given then the calibration image will be sought +in the list of images to be processed. +.le +.ls \fIflatcor\fR - Apply flat field correction? +The flat field images to be used are specified by the parameter +\fIflat\fR. There must be one flat field image for each filter +or subset (see \fBsubsets\fR) to be processed. If a flat field +image is not given then the calibration image will be sought +in the list of images to be processed. +.le +.ls \fIreadcor\fR - Convert zero level image to readout correction? +If a one dimensional zero level readout correction vector is to be subtracted +instead of a two dimensional zero level image then, when this parameter is set, +the zero level images will be averaged to one dimension. The readout axis +must be specified by the parameter \fIreadaxis\fR. The default for your +instrument is set by \fBsetinstrument\fR. +.le +.ls \fIscancor\fR - Convert flat field image to scan correction? +If the instrument is operated in a scan mode then a correction to the +flat field may be required. There are two types of scan modes, "shortscan" +and "longscan". In longscan mode flat field images will be averaged +to one dimension and the readout axis must be specified. Shortscan mode +is a little more complicated. The scan correction is used if the flat +field images are not observed in scan mode. The number of scan lines +must be specified by the parameter \fInscan\fR. If they are observed in +scan mode, like the object observations, then the scan correction +operations should \fInot\fR be specified. For details of scan mode operations +see \fBccdproc\fR. The scan parameters +should be set by \fBsetinstrument\fR. If in doubt consult someone +familiar with the instrument and mode of operation. +.le + + This description of the parameters is longer than the actual operation of +setting the parameters. The only parameters likely to change during processing +are the calibration image parameters. + + When processing many images using the same calibration files a modest +performance improvement can be achieved by keeping (caching) the +calibration images in memory to avoid disk accesses. This option +is available by specifying the amount of memory available for image +caching with the parameter \fImax_cache\fR. If the value is zero then +the images are accessed from disk as needed while if there is +sufficient memory the calibration images may be kept in memory during +the task execution. +.sh +3. Processing Your Data + + The processing path depends on the type of data, the type of +instrument, types of calibration images, and the observing +sequence. In this section we describe two types of operations common +in reducing most data; combining calibration images and performing the +standard calibration and correction operations. Some additional special +operations are described in the following section. + + However, the first thing you might want to try before any +processing is to get a listing of the CCD images showing the CCD image +types, subsets, and processing flags. The task for this is +\fBccdlist\fR. It has three types of output; a short one line per +image format, a longer format which shows the state of the processing, +and a format which prints the image names only (used to create files +containing lists of images of a particular CCD image type). To get a +quick listing type: + +.nf + cl> ccdlist *.imh + ccd001.imh[544,512][short][unknown][V]:FOCUS L98-193 + ccd007.imh[544,512][short][object][V]:N2968 V 600s + ccd015.imh[544,512][short][object][B]:N3098 B 500s + ccd024.imh[544,512][short][object][R]:N4036 R 600s + ccd045.imh[544,512][short][flat][V]:dflat 5s + ccd066.imh[544,512][short][flat][B]:dflat 5s + ccd103.imh[544,512][short][flat][R]:dflat 5s + ccd104.imh[544,512][short][zero][]:bias + ccd105.imh[544,512][short][dark][]:dark 3600s +.fi + + The example shows only a sample of the images. The short format +listing tells you the name of the image, its size and pixel type, the +CCD image type as seen by the package, the subset identifier (in this +case the filter), and the title. If the data had been processed then +there would also be processing flags. If the CCD image types do not +seem right then there may be a problem with the instrument +specification. + + Many of the tasks in the \fBccdred\fR package have the parameter +\fIccdtype\fR which selects a particular type of image. To list +only the object images from the previous example: + +.nf + cl> ccdlist *.imh ccdtype=object + ccd007.imh[544,512][short][object][V]:N2968 V 600s + ccd015.imh[544,512][short][object][B]:N3098 B 500s + ccd024.imh[544,512][short][object][R]:N4036 R 600s +.fi + +If no CCD image type is specified (by using the null string "") +then all image types are selected. This may be +necessary if your instrument data does not contain image type identifications. +.sh +3.1 Combining Calibration Images + + If you do not need to combine calibration images because you only +have one image of each type, you can skip this section. Calibration +images, particularly zero level and flat field images, are combined in +order to minimize the effects of noise and reject bad pixels in the +calibrations. The basic tool for combining images is the task +\fBcombine\fR. There are simple variants of this task whose default +parameters are set appropriately for each type of calibration image. +These are the ones you will use for calibration images leaving +\fBcombine\fR for combining object images. Zero level images are +combined with \fBzerocombine\fR, dark count images with +\fBdarkcombine\fR, and flat field images with \fBflatcombine\fR. + + For example, to combine flat field images the command is: + +.nf + cl> flatcombine *.imh + Jun 1 14:26 combine: maxreject + Images N Exp Mode Scale Offset Weight + ccd045.imh 1 5.0 INDEF 1.000 0. 0.048 + ccd046.imh 1 5.0 INDEF 1.000 0. 0.048 + <... list of files ...> + ccd065.imh 1 5.0 INDEF 1.000 0. 0.048 + ----------- ------ ------ + FlatV.imh 21 5.0 +.fi + +This output is printed when verbose mode is set. The same information +is recorded in the log file. In this case the flat fields are combined +by rejecting the maximum value at each point in the image (the +"maxreject" algorithm). The images are scaled by the exposure times, +which are all the same in this example. The mode is not evaluated for +exposure scaling and the relative weights are the same because the +exposure times are the same. The example only shows part of the +output; \fBflatcombine\fR automatically groups the flat field images by +filter to produce the calibration images "FlatV", "FlatB", and +"FlatR". +.sh +3.2 Calibrations and Corrections + + Processing the CCD data is easy and largely automated. +First, set the task parameters with the following command: + + cl> eparam ccdproc + +You may have already set the parameters when you ran +\fBsetinstrument\fR, though the calibration image parameters +\fIzero\fR, \fIdark\fR, and \fIflat\fR may still need to be set or +changed. Once this is done simply give the command + +.nf + cl> ccdproc *.imh + ccd003: Jun 1 15:13 Overscan section is [520:540,*] with mean=485.0 + ccd003: Jun 1 15:14 Trim data section is [3:510,3:510] + ccd003: Jun 1 15:14 Overscan section is [520:540,*] with mean=485.0 + FlatV: Jun 1 15:14 Trim data section is [3:510,3:510] + FlatV: Jun 1 15:15 Overscan section is [520:540,*] with mean=486.4 + ccd003: Jun 1 15:15 Flat field image is FlatV.imh with scale=138.2 + ccd004: Jun 1 15:16 Trim data section is [3:510,3:510] + ccd004: Jun 1 15:16 Overscan section is [520:540,*] with mean=485.2 + ccd004: Jun 1 15:16 Flat field image is FlatV.imh with scale=138.2 + <... more ...> + ccd013: Jun 1 15:22 Trim data section is [3:510,3:510] + ccd013: Jun 1 15:23 Overscan section is [520:540,*] with mean=482.4 + FlatB: Jun 1 15:23 Trim data section is [3:510,3:510] + FlatB: Jun 1 15:23 Overscan section is [520:540,*] with mean=486.4 + ccd013: Jun 1 15:24 Flat field image is FlatB.imh with scale=132.3 + <... more ...> +.fi + + The output shown is with verbose mode set. It is the same as +recorded in the log file. It illustrates the principle of automatic +calibration image processing. The first object image, "ccd003", was +being processed when the flat field image was required. Since the +image was taken with the V filter the appropriate flat field was +determined to be "FlatV". Since it had not been processed, the +processing of "ccd003" was interrupted to process "FlatV". The +processed calibration image may have been cached if there was enough +memory. Once "FlatV" was processed (note that the flat field was not +flattened because the task knows this image is a flat field) the +processing of "ccd003" was completed. The next image, "ccd004", is +also a V filter image so the already processed, and possibly cached, +flat field "FlatV" is used again. The first B band image is "ccd013" +and, as before, the B filter flat field calibration image is processed +automatically. The same automatic calibration processing and image +caching occurs when using zero level and dark count calibration +images. + + Commonly the processing is done with the verbose mode turned off +and the task run as a background job. This is done with the commands + +.nf + cl> ccdred.verbose=no + cl> ccdproc *.imh & +.fi + +The already processed images in the input list are recognized as having been +processed and are not affected. To check the status of the processing we +can look at the end of the log file with: + + cl> tail logfile + +After processing we can repeat the \fBccdlist\fR command to find: + +.nf + cl> ccdlist *.imh ccdtype=object + ccd007.imh[508,508][real][object][V][OTF]:N2968 V 600s + ccd015.imh[508,508][real][object][B][OTF]:N3098 B 500s + ccd024.imh[544,512][short][object][R][OTF]:N4036 R 600s +.fi + +The processing flags indicate the images have been overscan corrected, +trimmed, and flat fielded. + + As you can see, processing images is very easy. There is one source +of minor confusion for beginning users and that is dealing with calibration +images. First, there is no reason that calibration images +may not be processed explicitly with \fBccdproc\fR, just remember to set +the \fIccdtype\fR to the calibration image type or to "". When processing +object images the calibration images to be used may be specified either +with the task parameter for the particular calibration image or by +including the calibration image in the list of input images. Calibration +images specified by parameter value take precedence and the task +does not check its CCD image type. Calibration images given in the +input list must have a valid CCD image type. In case too many +calibration images are specified, say because the calibration images +combined to make the master calibration images were not deleted and +so are part of the image list "*.imh", only the first one will be used. +Another point to know is that flat field, iillumination, and fringe images +are subset (filter) dependent and so a calibration image for each filter +must be specified. +.sh +4. Special Processing Operations + + The special processing operations are mostly concerned with the +flat field response correction. There are also special processing +operations available in \fBccdproc\fR for one dimensional readout +corrections in the zero level and flat field calibrations. These +were described briefly above and in more detail in \fBccdproc\fR +and are not discussed further in this guide. The processing +operations described in this section are for preparing flat fields +for two dimensional spectroscopic data, for correcting flat fields +for iilluminations effects, for making a separate iillumination correction, +and for applying corrections for fringe effects. For additional +discussion about flat fields and iillumination corrections see the +help topic \fBflatfields\fR. +.sh +4.1 Spectroscopic Flat Fields + + For spectroscopic data the flat fields may have to be processed to +remove the general shape of the lamp spectrum and to replace regions outside +of the aperture where there is no flat field information with values that +will not cause bad response effects when the flat field is applied to the +data. If the shape of the lamp spectrum is not important and if the +longslit spectra have the regions outside of the slit either off the +detector or trimmed then you may use the flat field without special +processing. + + First you must process the flat field images explicitly with + + cl> ccdproc *.imh ccdtype=flat + +where "*.imh" may be replaced with any list containing the flat fields. +If zero level and dark count corrections are required these calibration +images must be available at this time. + + Load the \fBtwodspec\fR package and then either the \fBlongslit\fR +package, for longslit data, or the \fBapextract\fR package, for +multiaperture data such as echelles, multifiber, or aperture mask +spectra. The task for removing the longslit quartz spectrum is +\fBresponse\fR. There is also a task for removing iillumination +effects, including the slit profile, from longslit spectra called +\fBiillumination\fR. For more about processing longslit spectra see the +help for these tasks and the paper \fIReduction of Longslit Spectra +with IRAF\fR. The cookbook \fIReduction of Longslit Spectroscopic +Data Using IRAF (KPNO ICCD and Cryogenic Camera Data)\fR also provides +a very good discussion even if your data is from a different instrument. + + For multiaperture data the task for removing the relative shapes of +the spectra is called \fBapnormalize\fR. Again, consult the help documentation +for this task for further details. Since you will probably also be +using the package for extracting the spectra you may be interested +in the document \fIThe IRAF APEXTRACT Package\fR. +.sh +4.2 Iillumination Corrections + + The flat field calibration images may not have the same iillumination +pattern as the observations of the sky due to the way the lamp illuminates the +optical system. In this case when the flat field correction is applied +to the data there will be gradients in the sky background. To remove +these gradients a blank sky calibration image is heavily smoothed +to produce an iillumination image. The iillumination image +is then divided into the images during processing to correct for the +iillumination difference between the flat field and the objects. +Like the flat fields, the iillumination corrections images may be subset +dependent so there should be an iillumination image for each subset. + +The task which makes iillumination correction images is \fBmkskycor\fR. +Some examples are + +.nf + cl> mkskycor sky004 Illum004 + cl> mkskycor sky*.imh "" +.fi + +In the first example the sky image "sky004" is used to make the iillumination +correction image "Illum004". In the second example the sky images are +converted to iillumination correction images by specifying no output image +names. Like \fBccdproc\fR if the input images have not been processed they +are first processed automatically. + +To apply the iillumination correction + +.nf + cl> ccdproc *.imh ccdtype=object illumcor+ illum=Illum004 + cl> ccdproc *.imh ccdtype=object illumcor+ illum=sky*.imh +.fi + +The iillumination images could also be set using \fBeparam\fR or given +on the command line. +.sh +4.3 Sky Flat Fields + + You will notice that when you process images with an iillumination +correction you are dividing each image by a flat field calibration and +an iillumination correction. If the iillumination corrections are not +done as a later step but at the same time as the rest of the processing +one will get the same calibration by multiplying the flat field by +the iillumination correction and using this product alone as the +flat field. Such an image is called a \fIsky flat\fR since it is +a flat field which has been corrected to yield a flat sky when applied +to the observations. This approach has the advantage of one less +calibration image and two less computations (scaling and dividing the +iillumination correction). As an added short cut, rather than compute +the iillumination image with \fBmkskycor\fR and then multiplying, the +task \fBmkskyflat\fR does all this in one step. Thus, \fBmkskyflat\fR +takes an input blank sky image, processes it if needed, determines the +appropriate flat field (sky flats are also subset dependent) from the +\fBccdproc\fR parameters or the input image list, and produces an +output sky flat. Further if no output image is specified the task +converts the input blank sky calibration image into a sky flat. + + Two examples in which a new image is created and in which the +input images are converted to sky flats are + +.nf + cl> mkskyflat sky004 Skyflat + cl> mkskyflat sky*.imh "" +.fi +.sh +4.4 Iillumination Corrected Flat Fields + + A third method to account for iillumination problems in the flat fields +is to remove the large scale pattern from the flat field itself. This is +useful if there are no reasonable blank sky calibration images and the +astronomical exposures are evenly illuminated but the flat fields are not. +This is done by smoothing the flat field images instead of blank sky +images. As with using the sky images there are two methods, creating +an iillumination correction to be applied as a separate step or fixing +the original flat field. The smoothing algorithm is +the same as that used in the other tasks. The tasks to make these types +of corrections are \fBmkillumcor\fR and \fBmkillumflat\fR. The usage +is pretty much the same as the other iillumination correction tasks +except that it is more reasonable to replace the original flat fields +by the corrected flat fields when fixing the flat field. Examples +of an iillumination correction and removing the iillumination pattern +from the flat field are + +.nf + cl> mkillumcor flat025 Illum025 + cl> mkillumflat flat*.imh "" +.fi + +As with the other tasks, the input images are processed if necessary. +.sh +4.5 Fringe Corrections + + Some CCD detectors suffer from fringing effects due to the night +sky emission lines which are not removed by the other calibration +and correction operations. To correct for the fringing you need a +really blank sky image. There is not yet a task to remove objects from +sky images because this is often done with an interactive image display +tool (which will soon be added). The blank sky image is heavily smoothed +to determine the mean sky background and then this is subtracted from the +original image. The image should then be essentially zero except for the +fringe pattern. This fringe correction image is scaled to the same +exposure time as the image to be corrected and then subtracted to remove +the fringing. Note that since the night sky lines are variable there +may need to be an additional scaling applied. Determining this scaling +requires either an interactive display tool or a very clever task. +Such tasks will also be added in the future. + + The task to make a fringe correction image is \fBmkfringecor\fR. +the sky background is determined in exactly the same way as the iillumination +pattern, in fact the same sky image may be used for both the sky +iillumination and for the fringe correction. The task works consistently +with the "mk" tasks in that the input images are processed first if needed +and then the output correction image is produced with the specified name +or replaces the input image if no output image is specified. +As examples, + +.nf + cl> mkfringecor sky004 Fringe + cl> mkfringecor sky*.imh "" +.fi +.sh +5. Demonstration + + A simple demonstration task is available. To run this demonstration +load the \fBccdtest\fR package; this is a subpackage of the main +\fBccdred\fR package. Then simply type + + cl> demo + +The demonstration will then create some artificial CCD data and reduce +them giving descriptive comments as it goes along. This demonstration uses +the "playback" facility of the command language and is actually substituting +it's own commands for terminal input. Initially you must type carriage return +or space after each comment ending with "...". If you wish to have the +demonstration run completely automatically at it's own speed then type 'g' +a the "..." prompt. Thereafter, it will simple pause long enough to give +you a chance to read the comments. When the demo is finished you will +need to remove the files created. However, feel free to examine the reduced +images, the log file, etc. \fINote that the demonstration changes the +setup parameters so be sure to run \fBsetinstrument\fI again and check +the setup parameters.\fR +.sh +6. Summary + + The \fBccdred\fR package is very easy to use. First load the package; +it is in the \fBimred\fR package which is in the \fBnoao\fR package. +If this is your first time reducing data from a particular instrument +or if you have changed instruments then run \fBsetinstrument\fR. +Set the processing parameters for the operations you want performed. +If you need to combine calibration images to form a master calibration +image use one of the combine tasks. Spectroscopic flat fields may +need to be processed first in order to remove the lamp spectrum. +Finally, just type + + cl> ccdproc *.imh& +.sh +7. References + + A general guide to using IRAF is \fIA User's Introduction to the IRAF +Command Language\fR. This document may be found in the IRAF documentation +sets and is available from the National Optical Astronomy Observatories, +Central Computer Services (NOAO-CCS). + + A more detailed description of the \fBccdred\fR package including +a discussion of the design and some of the algorithms see \fIThe IRAF +CCD Reduction Package -- CCDRED\fR by F. Valdes. This paper is available +from NOAO-CCS and appears in the proceedings of the Santa Cruz Summer +Workshop in Astronomy and Astrophysics, \fIInstrumentation for Ground-Based +Optical Astronomy: Present and Future\fR, edited by Lloyd B. Robinson and +published by Springer-Verlag. + + The task descriptions and supplementary documentation are available +in printed form in the IRAF documentation sets, a special set +containing documentation for just the \fBccdred\fR package, and on-line +through the help task by typing + + cl> help \fItopic\fR + +where \fItopic\fR is one of the following. + +.nf + badpiximage - Create a bad pixel mask image from a bad pixel file + ccdgroups - Group CCD images into image lists + ccdhedit - CCD image header editor + ccdlist - List CCD processing information + ccdproc - Process CCD images + ccdtest - CCD test and demonstration package + combine - Combine CCD images + cosmicrays - Detect and replace cosmic rays + darkcombine - Combine and process dark count images + flatcombine - Combine and process flat field images + mkfringecor - Make fringe correction images from sky images + mkillumcor - Make flat field iillumination correction images + mkillumflat - Make iillumination corrected flat fields + mkskycor - Make sky iillumination correction images + mkskyflat - Make sky corrected flat field images +setinstrument - Set instrument parameters + zerocombine - Combine and process zero level images + + ADDITIONAL HELP TOPICS + + ccdred - CCD image reduction package + ccdtypes - Description of the CCD image types + flatfields - Discussion of CCD flat field calibrations + guide - Introductory guide to using the CCDRED package + instruments - Instrument specific data files + subsets - Description of CCD subsets +.fi + +Printed copies of the on-line help documentation may be made with the +command + + cl> help topic | lprint + + In addition to the package documentation for \fBccdred\fR, +\fBlongslit\fR, and \fBapextract\fR there may be specific guides for +certain instruments. These specific guides, called "cookbooks", give +specific examples and parameter values for the CCD data. +.endhelp |