\documentclass[11pt,letterpaper,dvips]{article} \usepackage{latexsym} \usepackage{fancybox} \usepackage{graphicx} \usepackage{amssymb} \usepackage{color} %\usepackage{amstex} \usepackage{ulem} \usepackage{float} \pretolerance=10000 \textwidth=7.0in \textheight=10.0in \voffset = -0.3in \topmargin=0.0in \headheight=0.00in \hoffset = -0.3in \headsep=0.00in \oddsidemargin=0in \evensidemargin=0in \parindent=2em \parskip=1.5ex \input{/home/xavier/bin/defs} \input{/home/xavier/bin/latex} \newcommand{\nnn}{ccd\#\#\#} \special{papersize=8.5in,11in} \renewcommand{\theenumi}{\Roman{enumi}} \begin{document} %\pagestyle{empty} \begin{center} {{\Huge \bf WFCCD Multi-Slit Reduction [v1.0]}} \end{center} \begin{enumerate} {\Large \item Requirements } \begin{itemize} \item IDL v5.4 or later \item $>$500M RAM \item $>$2G hard drive space \item The full software package, including the {\bf djs} and {\bf idlspec2d} codes \item Hopefully a 300MHz processor or better \item Slit mask information (ideally from Andy's maskgen program) \item Log sheets [somewhat optional] \end{itemize} {\Large \item Suggested Calibrations} \begin{itemize} \item 2 QTZ Lamps at position of science frames \item 1 Arc on each side of the science frames \item (Optional) Bias frames to check CCD performance \end{itemize} {\Large \item Initial Setup (Repeat for each night) } \begin{enumerate} \item Create a new directory for the night and enter it \item Create a Raw/ directory and put all the raw data in it. \item Create a pro/ directory and copy the files from $\$$XIDL/Spec/WFCCD/pro into it (e.g.\ {\it setcrds.pro, proc\_night.pro, extract\_night.pro}). {\bf These files can be used to run most of the steps that follow.} \item Launch idl in the directory above Raw/ \item {\bf wfccd\_strct} :: Create the wfccd structure. Again, I use the {\it proc\_night.pro} file to do this. This structure organizes the entire night of data and is the most important file created. The structure is listed on the next page [v1.1]. \\ The routine creates a few things: (1) an IDL structure in memory with whatever name you choose (e.g.\ night1); (2) the file 'struct.fits' which is a fits version of the structure; (3) the file 'wfccd.list' which is an ASCII version of the fits file which lists the values of some but not all tags. To view the structure outside of IDL (or even in general), I highly recommend the program 'fv' which I think stands for fitsview. It allows you to examine binary fits tables. \\ \quad Example: IDL$> \;$ {\bf wfccd\_strct}, night1, /MKDIR \\ \quad Time : $<1$s per image \item Modify the WFCCD structure :: The previous step creates the structure and takes a guess at the initial values of many of the tags based on the header card info. It is impossible, however, to automate all of the values for the tags and therefore the user must do a fair amount of this by hand. The file {\it setcrds.pro} is an extensive example. Note the IDL routine {\bf x\_fmidx} converts the frameno of an image to the index in the structure. \\ The obvious tags to modify are: \begin{enumerate} \item Obj :: Object name \item flg\_anly :: Include in analysis (defaulted to 1 for yes) \item type :: ARC, FLT, etc. (see the struct definition) \item masknm :: Generally a two character string giving the unique def \item mask\_id :: Long integer identifying a given mask. This is the most important \item msk\_fil :: Mask file describing the slits. You will always need to set this tag. Ideally, the output from Andy's {\it maskgen} program. I tend to put these files in the Masks/ directory. \end{enumerate} \item Updating the WFCCD structure :: In IDL you can modify the values of any of the tags. You can then save the structure in fits form and rewrite the ASCII file with the routine {\bf write\_wfccdstr}. \\ \quad Example: IDL$> \;$ {\bf write\_wfccdstr}, night1, FITS='name' \\ \quad Time : fast \item OV region :: By default, the package will assume 32 columns of overscan. If you use less, the program will behave fine. If you use more, they will be ignored. \end{enumerate} \clearpage \begin{center} {\Large {\bf wfccdstr}} \end{center} {\small \begin{tabular}{lcl} \hline Tag & Type & Comment \\ \hline frame & 0 & FRAME Number \\ flg\_anly & 0 & Analysis flag 0=Don't Analyse \\ Obj & ' ' & Object Name \\ type & ' ' & ObjTyp : OBJ, STD, DRK, ZRO, FLT, ARC, MSK, ALG \\ mask\_id & 0L & Mask ID \\ masknm & ' ' & Mask Name \\ exp & 0.d & Exposure time \\ filter & ' ' & Filter : U,B,V,R,I, C \\ filtpos & 0 & Filter Position \\ grism & ' ' & Grism : BG, RG, NO \\ aperpos & 0 & Aperture position \\ casspos & 0. & CASS pos angle \\ AM & 0. & Airmass \\ CCD & ' ' & CCD \\ TEL & ' ' & Telescope \\ gain & 0. & Gain \\ readno & 0. & Read Noise \\ date & 0.0d & Date of Obs \\ UT & ' ' & UT \\ RA & ' ' & RA \\ DEC & ' ' & DEC \\ Equinox & 0. & EQUINOX \\ rootpth & ' ' & Path of the Root \\ img\_root & ' ' & Root name (usually in Raw directory) \\ flg\_ov & 0 & OV FILE? 0=No, 1=Yes \\ img\_ov & ' ' & Name of OV file (with directory) \\ flg\_msk & 0 & Mask FILE? 0=No, 1=Yes \\ img\_msk & ' ' & Name of Mask file \\ flg\_final & 0 & Final File? 0=No \\ img\_final & ' ' & Name of Final img \\ nslits & 0 & Num of slits \\ ystrt & 0L & Column for initiating the trace \\ msk\_fil & ' ' & Name of the Mask info file (fits) \\ slit\_fil & ' ' & Name of the Slit info file (fits) \\ arc\_fil & ' ' & Name of the Arc image file (fits) \\ map\_fil & ' ' & Name of the Map image file (fits) \\ flat\_fil & ' ' & Name of the Flat image file (fits) \\ obj\_fil & ' ' & Name of object structure (fits) \\ \hline \end{tabular} } \vskip 0.2in {\Large \item Create bias frame (optional)} \begin{enumerate} \item As a check you might create a bias frame. At the moment the reduction process does not include the bias frame. \item Run {\bf wfccd\_bias}. This routine outputs an image 'Bias.fits' in the Bias/ directory. The routine creates and then deletes overscan frames for each image.\\ \quad Example: IDL$> \;$ {\bf wfccd\_bias}, night1 \\ \quad Example: IDL$> \;$ {\bf proc\_night}, night1, /MKBIAS \\ \quad Time : 3-5min \\ \item To check the Bias frame : {\bf xatv}, 'Bias/Bias.fits' \end{enumerate} \end{enumerate} \clearpage \noindent {\bf {\Large \quad 0. Mask Reduction}} \begin{itemize} \item The following routines all apply to a single mask. In general, this means multiple science exposures of one designed mask. One could break these up too, however. \item I suggest you create a .pro file like {\it proc\_night.pro} to guide the process. It provides a convenient way of stepping through the reduction. \item Most of the following routines take only the WFCCD structure and the {\it maskid} as inputs. \end{itemize} \begin{enumerate} {\Large \item Combine Flats } \begin{itemize} \item Generally, one has at least 2 flats per mask. To remove CR, if nothing else, I combine the images. \item Run {\bf wfccd\_mkflat} :: This routine uses {\bf x\_addtwoflats} to combine 2 flats if there are only two or {\bf x\_combine} for more than 2 flats. \item Output is 'Flats/Flat\_{\it maskid}.fits' \\ \quad Example: IDL$> \;$ {\bf wfccd\_mkflat}, night1, maskid \\ \quad Example: IDL$> \;$ {\bf proc\_night}, night1, maskid, /MKFLAT \\ \quad Time : $<1$min \\ \item Check the Flat: {\bf xatv}, 'Flats/Flat\_{\it maskid}.fits' \end{itemize} {\Large \item Create the Map} \begin{itemize} \item {\bf wfccd\_mkmap} :: This step produces a fits file which contains information relating the original data frame to one where the slits run straight accross the image. The 'straightened' image has the same number of total rows as the original. \item The main routine {\bf x\_traceflat} takes the following steps: \begin{enumerate} \item transposes the flat image \item creates a sawtooth image (shifts and subtracts) to highlight slit edges \item Keys on column (row) 400 to find all significant peaks in the sawtooth image \item Uses {\bf trace\_crude} to trace the slit edges \item Outputs a trace structure {\bf tracestrct} \end{enumerate} \item The user then interactively checks the various traces with the routine {\bf x\_ydtortgui}. \begin{itemize} \item You can resize this gui \item LMB : Stretches the contrast and brightness. \item RMB : Edit the ends of each trace. The program assumes you have chosen the nearest edge and changes good to bad or vice-versa. \item DELTRC : Delete a given trace altogether. \end{itemize} I advise you extend the RHS of traces where it is sensible as there is generally little signal out at these edges. This program is one of the most user intensive of the entire reduction package. I intend to automize it entirely \item Finally, I run {\bf x\_fit2dtrace} to fit a 2D polynomial to the traces and create a map of the transformation. I also create the inverse map. \item Output is 'Maps/Map\_{\it maskid}.fits' and 'Maps/Trc\_{\it maskid}.fits. The map files are saved as double images and take 67M memory. \\ \quad Example: IDL$> \;$ {\bf wfccd\_mkmap}, night1, maskid \\ \quad Time : 5min to check the trace + 5min for the Map creation \\ \item Check the Map \begin{enumerate} \item Read in the flat: \quad flat = mrdfits('Flats/Flat\_{\it maskid}.fits') \item Read in the map: \quad map = mrdfits('Maps/Map\_{\it maskid}.fits') \item Rectify: \quad rflat = x\_rectify(flat, map) \item Examine: \quad {\bf xatv}, rflat \end{enumerate} \end{itemize} {\Large \item Create the Slit Structure} \begin{enumerate} \item {\bf wfccd\_setslits} :: This step creates a slit structure which describes the slits in a mask in greater detail than the WFCCD structure. The user can interactively set the slit edges. This is important for dealing with slit overlap. Here is the structure: \begin{center} {\Large {\bf mslitstrct} } \end{center} {\small \begin{tabular}{lcl} \hline Tag & Type & Comment \\ \hline flg\_anly & 0 & Analyse? (1=yes, 0=no) \\ id & 0L & ID number \\ field & ' ' & Field name \\ length & 0. & (arcsec) \\ width & 0. & (arcsec) \\ pa & 0. \\ arcpix & 0. & Arcsec per pix \\ xyqso & fltarr(2) & x offset from the QSO (arcsec) \\ xpos & 0. & x position of silt \\ nobj & 0 & Number of objects in slit \\ ypos & fltarr(10) & y pos of obj relative to slit edges ($\%$) \\ yedg & fltarr(2) & Slit edges relative to slit mask cen (pix) \\ yedg\_flt & fltarr(2) & y-Edges of slit on CCD (Undistorted FLAT) \\ yedg\_orig & fltarr(5000,2) & Array of slit edges in orig \\ yedg\_sky & fltarr(5000,2) & Edges of slit for sky subtraction\\ \hline \end{tabular} } \vskip 0.2in \item Parse the slit file listed in the WFCCD structure under the 'msk\_fil' tag. You will need to have put your mask file in the appropriate place beforehand (e.g.\ 'Masks/'). The routine is {\bf wfccd\_prsslits}. The slit structure is created in memory. \item Straighten the Flat with the Map file (uses {\bf x\_rectify}). \item {\bf x\_setslits} :: Guess at the slit positions using the info in 'msk\_fil' \item {\bf x\_stsltgui} :: Unless NOVERIFY is set, launch a gui to interactively check the slits. It is important to set the silt edges about right. In particular, overlapping slits leads to a real problem with sky subtraction and they are best dealt with by identifying the slit edges properly. \begin{itemize} \item You can resize the display screen \item I would examine the LHS of the image where there is more flux \item The slit width is always preserved \item Red (blue) lines indicate the top (bottom) of a slit \item z (Z) zooms in (out) \item LMB sets contrast/brightness \item s (S) shifts all slits below the selected one (inclusive) and keys on top (bottom) of slit \item b (t) shifts one slit and keys on bottom (top) of slit \end{itemize} \item Map the slits into the original frame using {\bf x\_origslit}. The slit edge traces are written into 'yedg\_orig' in the slit structure. \item Output the Slit structure to 'Slits/Slits\_{\it mask\_id}.fits' \\ \quad Example: IDL$> \;$ {\bf wfccd\_setslits}, night1, maskid \\ \quad Time : $<5$min to check the slits \\ \end{enumerate} {\Large \item Normalize the Flat} \begin{itemize} \item {\bf wfccd\_normflat} :: Collapses (median) the slits in the flat using the slit edges from the previous step. Fits a high order bspline to the final result (with 5sig rejection). \item The main driver is {\bf x\_normflat}. \item The output is 'Flats/FlatN\_{\it mask\_id}.fits'. The WFCCD structure is updated to reflect the new flat. At this point the file 'Flats/Flat\_{\it mask\_id}.fits' is unnecessary (33M). I'd check the normalized flat before ever deleting it, however.\\ \quad Example: IDL$> \;$ {\bf wfccd\_normflat}, night1, maskid \\ \quad Time : $<3$min \\ \end{itemize} {\Large \item Create the Wavelength Image} \begin{enumerate} \item This sequence of steps (i) processes the arc images, (ii) creates a wavelength solution for the central row of each slit in the straightened frame; and (iii) finds the wavelength solution for each pixel and maps back to the original frame. \item {\bf wfccd\_procarc} :: Process each Arc image. OV subtract, flatten, straighten the slits. Output is 'Arcs/ArcR\_\nnn.fits' where \nnn\ corresponds to the orginal ccd frame number. \\ \quad Example: IDL$> \;$ {\bf wfccd\_procarc}, night1, maskid \\ \quad Time : $<1$min \\ \item {\bf wfccd\_allarcsol} :: Find the wavelength solution for the center of each slit to be analysed (alignment star boxes are skipped). This routine drives the program {\bf wfccd\_arcsol} which: \begin{itemize} \item Medians the 5 central rows of each slit \item Guesses the initial wavelength solution based on the slit position \item Calls {\bf x\_autoid} which is a $\chi^2$ minimization routine that automatically finds a wavelength solution given an initial guess, an arc spectrum, and a line list. By default we use the linelist 'wfccdB\_HeNe.lst' given in $\$$XIDL/Spec/Arcs/Lists \item Output is an Arc structure {\bf wfccdarcstr} which is output as a fits file 'Arcs/ArcS\_\nnn.fits'. It has the wavlength solution, arc spectrum, and a wavelength array for the center of each slit in the straightened frame. \quad Example: IDL$> \;$ {\bf wfccd\_allarcsol}, night1, maskid\\ \quad Time : $\approx 10$s/slit \\ \end{itemize} \item {\bf wfccd\_arcimg} :: Translate the wavelength solution from the center rows to the entire slit. This is the only procedure which is exposure sensitive. The main driver is {\bf x\_arcimage}: \begin{itemize} \item Identifies all 3$\sigma$ arc lines and traces them across the slit. \item It then calculates a unique wavelength solution for each row. \end{itemize} Finally, the program maps the wavelength solution back into the original frame. The routine is called once per exposure for a given mask. It matches each exposure with the nearest Arc frame by considering the UT of the images. The output is an Arc image 'Arcs/ArcI\_\nnn.fits'. \\ \quad Example: IDL$> \;$ {\bf wfccd\_arcimg}, night1, maskid, expsr \\ \quad Time : $\approx 1$min/exposure \\ \item {\bf wfccd\_chkarc} :: Plots the arc line solutions from each slit in a simple gui. Shows the RMS solution (\AA) and the red lines identify key arc lines. If something isn't right, you are in trouble!\\ \quad Example: IDL$> \;$ {\bf wfccd\_chkarc}, night1, maskid, expsr \\ \quad Time : fast \\ \item {\bf wfccd\_cleanarc} :: Zeros out bad wavelength values. These should only occur when two slits are too close or overlapping. This procedure helps with the sky subtraction and extraction.\\ \quad Example: IDL$> \;$ {\bf wfccd\_cleanarc}, night1, maskid, expsr \\ \quad Time : $<1$min \\ \end{enumerate} {\Large \item Process the Science Images} \begin{itemize} \item {\bf wfccd\_procobj} :: OV subtract, flatten and staple in the wavelength image. \item Produces one final fits image: 'Final/f\_\nnn.fits'. This file has Flux, Var, Wave in the first 3 data units (50Mb). \\ \quad Example: IDL$> \;$ {\bf wfccd\_procobj}, night1, maskid \\ \quad Time : fast \\ \end{itemize} {\Large \item CR Flagging} \begin{itemize} \item {\bf wfccd\_objcr} :: Identifies CR in the object frames by comparing two exposures. Currently can only take two images at a time but this is easily updated. A CR must have a flux $>3 \times$ the pixel in the other frame and a flux $> 200$.\\ \quad Example: IDL$> \;$ {\bf wfccd\_objcr}, night1, maskid \\ \quad Time : $< 2$min \\ \end{itemize} {\Large \item Clean Up} \begin{itemize} \item {\bf wfccd\_cleanup} :: Removes many of the unnecessary files that the package creates (e.g.\ the unnormalized flat). Don't run this unless you are quite confident your processing is complete.\\ \quad Example: IDL$> \;$ {\bf wfccd\_cleanup}, night1, maskid \\ \quad Time : fast \\ \end{itemize} \end{enumerate} \clearpage \noindent {\Large \quad 0. Mask Extraction} \begin{itemize} \item The following routines all apply to a single exposure \item I suggest you create a .pro file like {\it extrct\_msk.pro} to guide the process. It provides a convenient way of stepping through the reduction. \item Most of the following routines take the WFCCD structure, the {\it maskid}, and the exposure number as inputs. \end{itemize} \begin{enumerate} {\Large \item Create Object Structure} \begin{enumerate} \item {\bf wfccd\_mkobjstr} :: Creates the object structure which stores the spectra of all objects idenitified in the mask. \item Options: \begin{itemize} \item /NOSKY :: Will not modify the region for sky subtraction \item /NOCHK :: Will not run {\bf x\_setobjgui} \item /NOSLIT :: Will not modify the Slit structure \item /NOOBJ :: Will not modify the Obj structure \item SKYOFF :: Offset of sky edge from slit edge (default=2pix) \end{itemize} \begin{center} {\Large {\bf specobjstrct} } \end{center} {\small \begin{tabular}{lcl} \hline Tag & Type & Comment \\ \hline field & ' ' & Name of field \\ slit\_id & 0L \\ obj\_id & ' ' & ID value (a=primary, b-z=serendip, x=NG) \\ flg\_anly & 0 & 0=No analysis\\ exp & 0. & \\ xcen & 0L & Column where obj was id\\ ycen & 0. & \\ flg\_aper & 0 & 0=boxcar\\ aper & fltarr(2) & Widths of aperture, 0/1 = bottom/top (pixels)\\ skyrms & 0. & RMS of sky fit\\ trace & fltarr(5000) &\\ npix & 0L & \\ wave & fltarr(5000) & \\ fx & fltarr(5000) & \\ var & fltarr(5000) & $<=0$ rejected pix\\ flg\_flux & 0 & 0=f$_\lambda$, 1=f$_\nu$\\ flux & fltarr(5000) & Fluxed data\\ sig & fltarr(5000) & Err in fluxed data\\ date & 0.0d \\ UT & ' ' \\ img\_fil & ' ' \\ slit\_fil & ' ' \\ instr\_strct & ' ' & e.g. wfccdstr fits file\\ \hline \end{tabular} } \item The program first runs {\bf x\_fndslitobj} which automatically looks for the main science object (as defined in the Mask output file) and any serendipitous objects. \item The user should then run {\bf x\_setobjgui} to confirm the object locations and set the slit edges to their 'final' locations for sky subtraction. Rough centroid for the objects is good enough. {\it In general, sky subtraction works best on regions $\approx 25$ pix wide.} Beware of objects near the slit edge. Try to extend the sky regions beyond them. \begin{itemize} \item xatv-like display (use the Help window) \item Green (blue) lines trace science (serendipitous) objects \item Red crosses identifies the guess from the slit info \item 'm' moves the closest object to the cursor position \item 'd' deletes closest obj \item '{}[]' = pan up,down,left,right \item b (t) shifts the slit edge at the bottom (top) of slit \end{itemize} \item Output is 'Extract/Obj\_{\it maskid}.fits' and the Slit structure is updated.\\ \quad Example: IDL$> \;$ {\bf wfccd\_mkobjstr}, night1, maskid, expsr \\ \quad Time : 3min/exposure for slit+obj checking \\ \item {\bf wfccd\_editobjstr} :: Edit the Obj structure. Options: /NOOBJ, /NOSLIT. \\ \quad Example: IDL$> \;$ {\bf wfccd\_editobjstr}, night1, maskid, expsr \\ \quad Time : fast\\ \end{enumerate} {\Large \item Sky Subtraction} \begin{itemize} \item {\bf wfccd\_skysub} :: This procedure subtracts the sky from each slit, one by one. The main driver is {\bf x\_subskyslit} which does a LEGENDRE fit (the better of 2nd or 3rd order provided enough pixels) to each column after masking out the objects in the slit. It works on individual exposures. Currently, my routines do not handle objects right at the slit edge very well. \item Output is the sky subtracted 2D frame 'Extract/F\_\nnn.fits' with the appended Sky image and the rms of the fit along each column for each slit (35M).\\ \quad Example: IDL$> \;$ {\bf wfccd\_skysub}, night1, maskid, exposure \\ \quad Time : 20-30s/slit (roughly 10-15min) \\ \end{itemize} {\Large \item Extraction} \begin{enumerate} \item {\bf wfccd\_extobjbox} :: This procedure extracts the objects from the slits one by one. It works on individual exposures seperately. The main driver is {\bf x\_extobjbox} which \begin{enumerate} \item Traces the object with {\bf trace\_crude} \item Smashes the object to determine its profile \item Determines an aperture which includes 95$\%$ of the flux \item Identify pixels included in the aperture and what fraction \item Flags CR's by comparing the flux in a given column against the object profile. CR events have variance set to $-1$. \item Calls {\bf x\_rebin2dspec} which sums the flux into a 1D array with starting wavelength 3200\AA\ and $\delv = 100$km/s pixels \end{enumerate} \item All of the output is written to the object structure \\ \quad Example: IDL$> \;$ {\bf wfccd\_extobjbox}, night1, maskid, expsr \\ \quad Time : $<5$min \\ \item Run {\bf wfccd\_objsumm} to get a summary of the Fspec file. \end{enumerate} {\Large \item Check/Edit the Individual Spectra} \begin{itemize} \item {\bf wfccd\_chkspec} :: This routine plots up all of the objects in the object structure for a quick glance. It is a very simple gui. Bad extractions are easily identified and can be removed by adjusting the object structure 'by hand'.\\ \quad Example: IDL$> \;$ {\bf wfccd\_chkspec}, night1, maskid, expsr \\ \quad Time : fast \\ \item {\bf wfccd\_pltobj} :: This routine plots the spectrum and the 2D image together (very nice). You can examine the 'reality' of various emission and absorption lines. \\ \quad Example: IDL$> \;$ {\bf wfccd\_pltobj}, night1, maskid, expsr, [objnm] \\ \quad Time : 5s \\ \item {\bf wfccd\_editspec} :: This routine allows the user to set the variance of regions of spectra to 0 to eliminate them from further analysis. \\ \quad Example: IDL$> \;$ {\bf wfccd\_editspec}, night1, maskid, expsr \\ \quad Time : fast \\ \end{itemize} {\Large \item Flux the Spectra} \begin{itemize} \item {\bf wfccd\_fluxspec} :: This routine plots up all of the objects in the object structure for a quick glance. It is a very simple gui. Bad extractions are easily identified and can be removed by adjusting the object structure 'by hand'.\\ \quad Example: IDL$> \;$ {\bf wfccd\_fluxspec}, night1, maskid, [expsr] \\ \quad Time : fast \\ \end{itemize} {\Large \item Combine the Spectra} \begin{itemize} \item {\bf wfccd\_combspec} :: This routine combines multiple object structures (primarily their spectra) into one Final structure. For objects with multiple spectra, the spectra are matched to the same flux and summed. At the moment this routine only handles two spectra at a time. \\ \item Output :: A structure containg all of the fluxed, coadded spectra with name : {\it 'Extract/Fspec\_maskid.fits'}. \quad Example: IDL$> \;$ {\bf wfccd\_combspec}, night1, maskid \\ \quad Time : fast \\ \item Run {\bf wfccd\_fspecsumm} to get a summary of the Fspec file. \item Run {\bf wfccd\_chkfspec} to view the Final spectra \\ \quad Example: IDL$> \;$ {\bf wfccd\_chkfspec}, 'Extract/Fspec\_maskid.fits'\\ \quad Time : fast \\ \end{itemize} {\Large \item Solve for Redshifts} \begin{itemize} \item {\bf wfccd\_zfind} :: This routine drives the SDSS {\bf zfind} routines and uses the SDSS eigenspectra (rebinned to WFCCD pixel scale) to automate redshift identification. It is a $\chi^2$ minimization routine and it works rather well. Like all $\chi^2$ routines, however, it tends to fail when there are particularly bad regions of data. The ZANS structure in the Fspec structure is updated. \\ \quad Example: IDL$> \;$ {\bf wfccd\_zfind}, night1, maskid \\ \quad Time : Long, $\approx 30$s per obj \\ \item Run {\bf wfccd\_chkfspec} with the /ZFIND switch to view the Final spectra + \\ \quad Example: IDL$> \;$ {\bf wfccd\_chkfspec}, 'Extract/Fspec\_maskid.fits', /zfind \\ \quad Time : fast \\ \end{itemize} \end{enumerate} \end{document}