WQED User`s Manual - Astronomy Program
Contents
1. indeed the more cards included the easier it will be to figure out what the data in the file refers to The data part of the format consists of rows of numbers The zeroth column is the number of seconds between the time indicated by by the keyword UTC in the header and the midpoint of Mhttp en wikipedia org wiki Shoemaker_levy_9 15 the current exposure The next 8 columns give the observed number of sky subtracted counts from a single star for the exposure There is two restriction of the format of this number It must be positive definite and machine readable as a double precision floating point number So 12 12 12 0 12 3456 are all acceptable as is 1 23456e1 Using d is not acceptable for exponential notation The final column is an estimate of the sky flux The reduced file has a slightly different format The data section consists of two columns time as before and flux in units of fractional amplitude To convert a flux to fractional amplitude divide by the average flux and subtract 1 Fluxes given in fractional amplitudes may be negative 6 6 Working with raw data in different formats As described in the Tutorial the Wqed package provides a script for dealing with the output of the ccd_hsp IRAF routine called chooselc We also provide a number of other scripts which may be useful in converting the format of data from other sources When manipulating data files awk is typically the most useful tool available You2. Then the two channels can be divided as normal To begin you must create a wqed file from the qed file as described above The reduction process when wqed is run using the q flag is as follows Mark Sky Hit M to mark all the sky regions of each channel Subtract Sky For each channel hit P to interpolate the sky region and subtract it from the data Notice this is not the same as S described above for three channel phototube data The sky is created by averaging all the points in each section then drawing a straight line between the different sky sections If only one sky section is selected the mean value of those points are removed All regions that were previously sky will now be set as Garbaged points The rest of the reduction process is as before You can divide the two channels and garbage any bad points as normal 6 3 Adding a new observatory to Whiff To add a new observatory you must edit the file called wet whiff dat The telescope infor mation for the mcdonald observatory would look like Information for Mcdonald mcdo McDonald Observatory 13 instrument INSTRUME observer OBSERVER exptime EXPTIME object OBJECT date DATE OBS utc UTC filter FILTER utcstyle 1 datestyle 1 timefrac 0 ArgosRun RUN C ArgosRun Argos Run Info END Each observatory listing in this file must contain the following features 1 The line before you start your observatory must begin with a The rest of the line is ignored
3. and all points outside this region will be removed Unhappy with your selection Use CTRL U to undo a step Most actions which change the lightcurve can be undone The maximum number of undo steps is currently set at 30 Two other useful operations are division and trend fitting To divide channel one the target star by channel 2 a reference star first select the first channel 1 then select the divide command and then type 2 followed by ENTER You will see that small bumps and wiggles in the divided lightcurve are removed but more serious cloud does not divide out well Often you will find that parts of the divided lightcurve should be garbaged Be sure to check for very high data points that may not appear on the screen If a point lies off the screen it will be indicated by an arrow A lightcurve can be divided by the sum of two more more channels For example to divide Channel 1 by the sum of Channels 2 and 3 select Channel 1 select the divide command then type 2 and 3 before hitting enter Stars typically looked at by the WET are very blue Most comparison stars are red and so are extincted differently at different air masses This often manifests as a slight curvature in the divided lightcurve The size of this affect can be calculated but it is quicker and just as effective to remove this trend by fitting a low order polynomial To fit a trend to the data select the channel of interest type F and selec
4. ignore n lines of header with the flag i n This option implicitly sets the b flag wqed file wq i 10 3 4 2 Reductions Having successfully calculated the barycentric correction Wqed now searches for previous reduc tions If it finds any it will prompt you to delete them This is probably a good idea because Waed will append any new reductions to those files If you want to keep your old reductions hit N for No and quit without reducing A pgplot window will now appear see Figure 1 The white dots are the target star channel blue dots are the sky channel and other coloured lines are reference stars The average counts from each star is displayed in the appropriate colour on the left margin Some information about the run is at top and a text window at the bottom displays important messages The most recent message instructs to user to Type for a list of commands Highlight the pgplot window and type This will cause short help message to be displayed in the xterm window Select the red channel by hitting 2 Hide that lightcurve by hitting H Re show the lightcurve by hitting H again Repeat the process for the green light curve by hitting 3 Some users may prefer to see lightcurves plotted as solid lines instead of just as dots Toggle connected lines using C 5While you should feel free to add new objects to stars dat you should not edit the file leapseconds dat If the file needs to be updated use the
5. may find these two tools useful days2sec converts the first column of a file from units of days to units of seconds pickle is the interactive interface for examining a number of different lightcurves used by chooselc Takes in input file and plots 3 columns of that file at a time on the screen Hit ENTER to see the next lightcurve and Backspace to go backwards 6 7 Barycentric Corrections For each run Wqed calculated a barycentric correction based on four pieces of information The date and time of observation taken from the header the position of the star taken from stars dat and the difference between UTC and UT taken from the file leapseconds dat Because any of these sources of information may in error the barycentric correction is written only to the header so that correcting it at a later date is significantly easier The corrections themselves are calculated using the method of Stumpff 1980 A amp AS 41 1 This is the same method used by two older programs used by the Whole Earth Telescope QED written by Ed Nather and XQED written by Reed Riddle The relevant code in Wqed is taken directly from XQED 6 7 1 Errors in Wqed 1 0 Despite our bests efforts three small bugs crept into the previously released version of Wqed These bugs do not significantly change the barycentric calculation and we provide a tool to test and correct your previously reduced data e Leapseconds were not correctly applied on the day they
6. name If none exists you may use the s flag provided with whiff The keyword datestyle is 1 for dates formatted as yyyy mm dd 8 2 for yyyy mm ddThh mm ss and 3 for dd mm yyyy The keyword utcstyle is 0 if the time should be extracted from the date used with datestyle 2 and 1 if your time is hh mm ss ss The whiff keyword timefrac is the fraction of the exposure time when the time was written as measured from the beginning of the exposure For the time written at the start of exposure timefrac 0 for the time written at the end of exposure timefrac 1 The whiff keywords that are reserved for values that are always included in the header are instrument observer and filter These keywords create the information found in Instrument Observer and Filter of your Wqed header You may add any keyword you like by creating a whiff keyword by that name See ArgosRun above The final header created by whiff will contain the keyword ArgosRun and the value will be the value contained in RUN of the fits file provided To add a comment to your new keyword Syyyy mm dd and yyyy mm dd also work with datestyle 1 hh mm ss ss and hh mm ss ss also work with utcstyle 1 14 supply a whiff keyword that begins with a C For this example we have included the keyword C ArgosRun Whatever you enter for that keyword will appear in the comments section of the ArgosRun key Finally we note that the complexity in whiff reflect
7. various apertures and produces the star sky files The Iraf routine mark should be run on the first image by typing in into the fname parameter The type go to run the routine Instructions are provided in your xterm Basically activate the ds9 window and type w over each star Type r to close the file and q to quit It will then prompt you to hit return to examine the coordinates you specified If you are happy leave the vi window with a wq and type yes Otherwise type no and try marking again This creates a phot coords file that is used by phot to do your aperture photometry The Iraf routine setjd calculates the Julian date of each file Run this on at least one file in your series to make sure it is working correctly You need a date time and observatory in your header to get it to work correctly Specify which Fits keywords to use for the Date and the UTC If the Date also contains UTC it will use that instead of whatever keyword you type into the UTC blank This will use the OBSERVAT keyword to specify your observatory Make sure your OBSERVAT equals a known IRAF observatory You can either change the name in your headers to something recognized by IRAF or you can add your name to the iraf noao lib obsdb dat file The Iraf routine hsp_nd performs the aperture photometry You must create a list of fits images preferably in the order of time taken specified as list_fil Then create a base output name for base_out the progra
8. will appear indicating the amplitudes of peaks which are 99 likely to be real i e not noise peaks and 99 9 real Peaks below the green line should be treated with suspicion unless corroborated by other data Saving plots and data Use h to save an image of the currently displayed plot and s to save a copy of the current pre whitened lightcurve Fitlc has a couple of other useful options consult the help menu 4 4 fitdata fitlc has a command line cousin fitdata This can be useful for fitting precise periods to data and is useful for analysing many runs in batch mode For example to non linearly fit the period 302 2312424 s to a data set try fitdata nlsf f mcdo071110 037 1c1 302 2312424 Fitdata s many other options can be viewed by typing fitdata on the command line with no arguments 4 5 dodft dodft is a command line Fourier transform program used by wqplot but also available for general use The simplest usage is just dodft mcdo071110 037 1c1 which will produce an FT between 0 Hz and the Nyquist frequency oversampled by a factor of 10 There are a number of options for controlling both the input and output that can be listed by typing dodft with no arguments 5 Combining Multiple Runs The purpose of a WET run is to combine data from telescopes all over the world for analysis and WET provides two tools for achieving this Combining different runs is made easier because Waed inserts two keywords into th
9. BjedCorr are the values of the respective header keywords and t is the time in seconds of the i exposure The main body of the output file has two columns time in seconds and normalised flux T Bjed x BjedCorr 1 3 4 4 Wqed command summary Here is a quick reference for the more utilized commands in Wqed Help Undo last command Ctrl U Dividing one channel by others Smooth Gaussian smooths data with a kernel of std deviation of nn seconds where nn is input by the user Usage nn ENTER Garbage bad points g to garbage points inside a box of one channel Shift g specify an x range of points to garbage for all channels Ctrl g garbage points outside of a box in one channel Despite the best of intentions mistakes can be made calculating Barycentric corrections whether it is incorrect coordinates or a forgotten leapsecond By putting Bjed in the header but not changing the times for each data point we make it easier to correct a Bjed when necessary Bridge across garbaged points in selected channel B Bridging is sometimes useful if there is a small gap in a reference star but its use on a target star should be frowned upon Zooming in and out z uses your mouse location to zoom in by drawing a box Shift z zooms out x zooms in the x direction Shift x zooms out in the x direction u goes to the original zoom level Fit polynomial and remove from specified channel F Navigation amo
10. Help Document for Wqed and the WET Reduction Suite Susan E Thompson amp Fergal Mullally July 21 2009 1 General Idea As reductions go time resolved photometry is one of the easier problems in astronomy The problem for the Whole Earth Telescope WET is one of standardisation During a WET run data is pouring into headquarters from all over the world and every minute of the day and night Each telescope may have a different camera different software and different conventions and it all needs to be reduced and analysed quickly Afterwards the data needs to be stored in a manner that makes it possible find a given dataset and to easily determine what was observed where and when Many of the problems faced by the WET in this regard are experienced on a smaller scale by individual observers Data collection can be broken into the following steps Acquisition Taking the data Calibration Dark subtraction Flat fields etc Extraction Turning fits files into light curves Correction Removing the effects of clouds etc Analysis Making sense of it all The WET typically performs calibration and extraction with IRAF and Antonio Kanaan s ccd_hsp package The Wgqed suite is useful for the last two steps correction and analysis The goal is to take the output of Antonio s routines one or more runs from one or more telescopes and create a light curve LC and Fourier Transform FT Whiff uses the information stored in t
11. Move the mouse to the desired frequency and hit F A sine wave at the given frequency will be fit to the data and the results output to the xterm window Do a Non linear Fit Move the mouse to the desired frequency and hit N The data is first fit linearly and the results of the linear fit are used as initial conditions to a Marquant Levenberg non linear least squares solution The result is output to the xterm window Multiple Non linear Fit Select multiple frequencies using M and hit ENTER to do a simultaneous non linear least squares solution Prewhiten To subtract the most recent fit from the data hit P The lightcurve display is updated and the Fourier Transform is recalculated 10 Refresh FT Calculating FTs is a slow process To speed up analysis fitlc only calculates the FT for the visible window and calculates a maximum of 4000 points regardless of the resolution To see a portion of the FT in greater detail zoom in on that region and hit R Show Combination and Harmonic Frequencies Select an interesting frequency in your FT by moving your mouse over it and type C Thin vertical white lines will appear denoting the frequency of the first second and third harmonics of that frequency Select a second frequency hit C and thin colour lines will indicate sum and difference frequencies Show False Alarm Probabilities Select a region of the FT free of obvious peaks using 9 Red and green dashed lines
12. aders where the time is off by more than 10ms The usage is simple wqverify filel Icl file2 lc1 will calculate the correct bjed for each file and compare to the value in the header warning when a discrepancy is found To fix a header type waqverify f filel lcl The old header is saved to filel hd for comparison 6 8 Known Bugs or undesireable features When given a data file with more than 10 columns Wqed will crash on exit No data is lost in this crash 6 9 Reporting bugs We welcome bug reports on Wqed and endeavour to fix them as quickly as possible Email bug reports to sthomp physics udel edu When reporting bugs please be as detailed as possible to help us track down the source of the problem Always include the copies of the input files used to discover the bug and a description of what went wrong If a program crashes please also send the core dump To enable core dumps type ulimit c unlimited before running the offending program 7 Installation of PGPLOT and PGPERL 7 1 PGPLOT Detailed instructions for installing pgplot are given at www astro caltech edu tjp pgplot install html and we recommend you read them The overall procedure is as follows Download the distribution files to some directory e g opt Untar pgplot using tar zxvf pgplot5 2 tar gz Create a target directory for the compiled pgplot For this example we will use opt local pgplot In opt pgplot drivers list uncomment the drivers you want by r
13. and can serve as a comment 2 The first line after the must contain the 4 letter observatory code followed by the name you want written to the Telescope keyword in your Wqed header 3 The value on the left is the whiff keyword the value on the right is the keyword from the FITS file except for utcstyle datestyle timefrac and any keyword begining with C The meaning of utcstyle etc are explained below in 86 3 1 4 The end of the observatory information is signified with a line beginning with END 5 Any line beginning with a is ignored when reading in telescope information Keywords beginning with C are comments For example C ArgosRun is the comment to accompany the keyword ArgosRun in the output header You may tell whiff to use a different file for the observatory information by running whiff with the f flag 6 3 1 Whiff Keywords Whiff uses keywords to link pieces of information with the desired FITS keyword Several of these are required to successfully run Wqed some are reserved and always printed by Whiff and others you can add so they are put in your Wqed header The whiff keywords you must specify are exptime date object utcstyle datestyle timefrac and usually utc The keyword exptime should be followed by the Fits keyword containing the exposure time in seconds The keyword date should be followed by the Fits keyword containing the utc date The keyword object should be followed by the Fits keyword containing the star s
14. common among Unix like systems It requires C and Fortran compilers to install It also requires Perl and the pgplot package to run The pgplot extensions to perl are also necessary to run some of the scripts 2 2 Obtaining the Package The package can be downloaded as a tar ball from http www physics udel edu darc If you want to contribute to the code either with bug fixes new features or improvements to the manual you will need access to the subversion repository Talk to Susan or email her at sthomp physics udel edu 2 3 Installation On most systems pgplot will be the only required component not already installed Pgplot is a set of plotting routines written in Fortran that is popular with many astronomers Pgplot can be downloaded from www astro caltech edu tjp pgplot It comes with some fairly detailed instructions and we provide some additional help in 7 Follow the installation instructions ensuring that you also compile the C bindings To compile and install Wqed and its associated programs download the package from the url given above Unpack it using tar tar zxvf wqed tgz Waed needs two pieces of information to install correctly and you need to find these yourself The first is the location of the file libX11 so Try locate libX11 so or failing that find usr name libX11 so If you have a working X11 environment you definitely have this file so keep looking The second piece of information is the loca
15. ct your lightcurve If you prefer to use some other package it will be helpful to know what the format of the expected output is so you can adapt your output if necessary Alternatively you can skip to 6 5 to see the specification of the Wqed data format Antonio s routines produce a number of files with the extension star sky one per aperture size used in his extraction Each line of the file stores the information for a single image The first column is the julian day of the exposure as extracted from the fits header Each succeeding pair of columns lists the sky subtracted flux from a star and the sky flux that was subtracted from the star 3 1 Some example data We have included some example data in the directory example There is data from two telescopes hawaii and mcdonald in two subdirectories Both telescopes observed the same star G38 29 For each telescope we provide a single fits file and the lightcurve output of ccd_hsp for different apertures We will use the data from McDonald in our example 3 2 Choosing the optimal aperture Antonio s routines reduce all marked stars in a field with a number of different apertures one aper ture per output file For the McDonald data these files are called g3829_mcdonal_20071110_ star sky where is the aperture size used The first step is to choose the extraction with the optimal aperture size chooselc g3829 a d Chooselc will consider every file t
16. e header indicating the barycentric time of start of run bjed and the rate of change of bjed with respect to UTC Weld applies the barycentric correction to multiple lightcurves The default is to use the Bjed and BjedCorr keywords in your header However you can specify other keywords if necessary It can either take a file with a list of light curve files or you can type in a list of files Weld outputs the barycentric corrected times and flux for each file in temporal order i e the file with the earliest start time is output first The Barycentric time of the first data point is subtracted from each time unless you specify the t flag The times are assumed to be in seconds as output by Wqed The algorithm that calculates these lines has not be properly tested and may not be correct Do not use these lines in a refereed publication 11 5 0 1 Usage Usage weld filelist k Bjed 1 BjedCorr o outname t zero time b f files c cuts To weld together all the files listed in a file called list using Bjed for the zero times and BjedCorr for the linear correction in Bjed and output to list lc weld list o list lc To weld together all the lc1 files in the wet directory and output to a file called wet lc weld o wet lc f lc1 To create a file with times in days instead of secions weld list b 5 1 Cutting out data from your light curve Sometimes after you have all your light curves together you would like to
17. eate a postscript file of your image The r flag allows you to specify the range of the FT 4 2 waqreport Wareport provides an interface to quickly view the header information for all the runs in a directory The command wqreport Recursively searches the current directory for files with the extension lcl and outputs the value of the keywords Date UTC Observatory Object and Exposure time It also calculates the length of the run i e time between the first and last data point in a file The last column is the name of the file The output is formatted to fit on one line of an 80 column terminal window If you want to search for files with a different extension use the w flag wqreport w lc2 If you want to search a directory other than the current one provide the desired directory as an argument wqreport data telescopel 4 3 fitlc After reducing a run use fitlc to interactively examine the lightcurve and its FT Type fitle mcdo071110 037 1c1 An FT of the data will appear in the pgplot window previously used by Wqed Movement commands available in Wqed are reproduced in fitlc The following commands are also useful Toggle Lightcurve display Hit L to toggle between lightcurve and FT The most recent fit to the data will be displayed as a solid red line in the light curve display Show Window Move the mouse to the desired frequency and amplitude and hit W Use B to blink between window and FT Do a Linear Fit
18. ed from CCDs While advances in technology not to mention newer versions of Windows rendered qed obsolete the basic user interface was sound and was largely copied in Wqed Users familiar with ged should feel at home in Wged although some features have improved and others e g extinction correction have not been implemented Waed stands for Wet Qed and is pronounced wicked 3 4 1 Start up To run Wged on our recently created file simply type wqed mcdo071110 03 wq On startup Wqed reads two configuration files necessary for calculating barycentric correc tions stars dat and leapseconds dat both of which should be stored in HOME wet stars dat is a list of star names and their right ascension and declination leapseconds dat is a list of all leapseconds applied to UTC and when they were applied Improperly corrected times are a menace to time resolved astronomy and so Wqed will halt if these files are not found If for some reason you badly need to reduce data without proper timings use the b flag but do so with caution wqed file wq b Having found its configuration files Wqed then tries to determine what object was observed in this run and when by reading the keywords Object UTC and Date from the header If one of these lines is not found Wqed will complain and quit Override this behaviour with the b flag Finally if you have a file with a non standard header that Wqed cannot understand you can instruct Wqed to
19. emoving the Wqed requires XSERVE GIF and CPS We recommend you also uncomment VGIF PS VPS VCPS and XWINDOW We have often experienced difficulty when trying to install bindings for PNG Change to your target directory opt local pgplot and run the makemake command as speci fied by pgplot An example of this would be opt pgplot makemake opt pgplot linux g77_gcc The exact command depends on your operating system and available compiler Type make and make clean Test the installation by running pgdemol 17 Install the C bindings to pgplot by running make cpg C bindings are required for Wqed Environmental Variables You must add two variables to your shell envirnoment If you are using bash add the following to your bashrc file LD_LIBRARY_PATH LD_LIBRARY PATH opt local pgplot export LD_LIBRARY_PATH PGPLOT_DIR opt local pgplot export PGPLOT_DIR For C shell add the following to your cshrc file setenv LD_LIBRARY_PATH LD_LIBRARY_PATH opt local pgplot setenv PGPLOT_DIR opt local pgplot Test the cpgplot installation by running cpgdemo A demonstration program showing the capabilities of pgplot should run Note you can install pgplot as an ordinary user and only need to do it as root if you wish for every user on your machine to have access to pgplot 7 2 PGPERL To install pgperl the perl bindings to the pgplot installation you must install both the fortran to perl converter ExtUtils F77 and the
20. hat starts with the string g3829 The a indicates that the data is in the format alternating columns of star and sky The d flags instructs chooselc to divide the first star column by the second star column For an undivided lightcurve omit this flag A pgplot window will open with 3 panels showing a lightcurve from 3 different files Use Enter and Backspace to page through the lightcurves or left and right click with your mouse Z and SHIFT Z zoom in and out and U and D to scroll up and down Hit to see this list of commands When you are satisfied hit Q to quit A list of the files examined will be displayed in your xterm Type the number beside your preferred file The output file will be called g3829_mcdonal_20071110_12 sec and the times have been converted to seconds 3 3 Creating a Header with Whiff The purpose of Whiff Wet Header from Initial Fits File is to read the header of a fits file and create a WET header containing information pertinent to a run in a simple but standard format that can be easily read by both humans and machines The format of a WET header is described in more detail in 6 5 The usage is whiff file fits o observatory file fits is the fits file for the first image in the lightcurve For our example we will type whiff A1618 0001 fits o medo The header is saved to a file with the extension head If you have already created the sec file above you can create a WET format ligh
21. he fits header of an image to create ascii header text used to keep track of your data Wqed allows you to manipulate the data dividing by reference stars to remove the effect of cloud removing bad points etc It also calculates the barycentric correction Weld and Wmd provide two different options for combining data from different runs A number of scripts provide some lightweight analysis tools Although written for use by the WET the various tools in the package should be easy to adapt and use for reducing other variable star time series data 1 1 Changelog since version 1 0 e Fixed two small bugs in how barycentric corrections are calculated See 6 7 1 for more details e Added support for reducing 3 channel phototube data See 6 2 1Barycentric correction is the difference between the observed time of an event and the time that event would be observer at the centre of mass of the solar system Output files includes information on how barycentric correction is calculated to help find errors e A new script update leapseconds keeps the leap seconds file up to date fitlc and fitdata now apply the barycentric corrections to data if available Fix bug in whiff where the first day of the year was handled incorrectly e Improved support for gcc version 4 3 2 e Numerous bug fixes that reduced memory leaks and improved stability 2 Installation 2 1 Requirements The WET reduction suite is written for the X11 environment
22. m will attache the apeture sizes to this name Pick the method to follow the stars previous cross or 2dcross previous is the quickest method Then pick your apeture radii with diaf_beg and diaf_end and diaf_stp The sky radius is determined by annulus and dannulus Since you already marked your stars make mark_int no Following the stars is the tricky part Previous is straight forward you can however change the box size in which to search for the star with the ceterpars function Change cbox to a reasonable box width If you use cross you need to also change parameters in immatch Put two of your images in the images and reference parameters Then pick an section size to do the cross correlation in the form x1 x2 yl y1l When you run go you should see to not quite overlapping peaks 2dcross takes forever and should only be run if nothing else has worked When hsp nd is finished working you will have star sky files that can be used for the begining of the Wqed pipline as described above 4 Quick analysis 4 1 waplot After reducing a run you will have a light curve with a WET header The first thing you will want to do is plot the reduced light curve and its Fourier Transform The quickest way to do this is with wqplot You provide the light curve and it will take the FT with a program called dodft and produce a plot wqplot mcdo071110 037 1c1 w o file ps r 0 10000 Use the w flag to see the window of the FT The o flag will cr
23. n necessary from USNO ftp maia usno navy mil ser7 tai utc dat It is your responsibility to download the latest version of this file whenever a new leapsecond is applied 6 5 Data format The Wqed data format is designed to be easy to read by both machines and humans A Wqed file consists of two parts a header and data The header is composed of a series of cards each containing a key value and comment The format in C syntax is 15s 7 34s 27s n key value comment This means that card starts with a symbol a left aligned string of exactly 15 characters for the key an equals sign a string of exactly 34 characters for the value a second followed by up to 27 characters of a comment followed by a newline character Actually all characters from the second to the newline are optional so the following are all legal cards Telescope McDonald 82 in Telescope Name n Telescope McDonald 82 in Telescope Name n Telescope McDonald 82 in n Telescope McDonald 82 in n At a minimum three cards are required for a legal header Object Date and UTC UTC is the Universal Time Corrected of the midpoint of the first exposure time The format for date is YYYY MM DD while time is HH MM ss Sss where the fractions of a second are optional For example the initial impact of comet Shoemaker Levy 9 and Jupiter occured on Date 1994 07 16 and UTC 20 15 00 There is no limit on the number of other cards that can be included
24. nder development and will be more complete in later versions To reduce data taken with three channel photometers it must first be converted to the Wqed format For the most common three channel data format Quilt we provide a script to perform this conversion To use simply type qed2waed file qed The output will be stored in a file called quiltfilewq Run Wqed on this output file using the q flag to initialise three channel mode Additional functionality is then available Mark Sky Hit M to mark a region of the currently selected lightcurve as a sky observation Mark Sky in All Channels Hit SHIFT M to mark a region of all lightcurves as sky Subtract Sky Hit S to subtract the sky channel from the currently selected lightcurve If a region of the data has been marked as sky the relative sensitivity of the two phototubes is taken into account when performing the subtraction Subtract Sky from All Channels Use Shift S Set Sky Channel Wqed assumes the last column in the input file is the sky channel If this is incorrect hit Ctrl S and select the correct channel 6 2 Reducing 2 channel phototube data Waed also has limited support for reducing two channel phototube data This feature is under development In the case of 2 channel observations no sky channel exists The observer occasionally moves off the stars and observes the sky Wqed marks the sky and interpolates between the points to estimate a sky for each channel
25. ng your light curves o or l move the selected channel up and down or or increase or decrease the y scaling of the selected channel lt or gt scroll right and left Output Saving your results w Write one channel Shift w Write the first two channels e After hitting W or Shift W use E to save the entire lightcurve If you tell Wqed to write a particular channel more than once it will append the file If you make a mistake saving a file delete the current output file eg abc lcl and write the output again 3 5 Antonio s Routines While we do not support Antonio s routines we use their output as the input to the final reduction pipeline For completeness here we quickly describe how to use Antonio s routines to produce the star sky files Antonio s routines are based on IRAF They are designed to let you mark the stars on the first fits image you have perform aperture photometry at different aperture sizes calculate the Julian date of each frame and follow the stars as they change position in each frame You must run Antonio s routines by running iraf from the directory with the correct login cl one has probably been created for the observatory whose data you are reducing The basic steps of Antonio s Routines are mark Used to select each star in the first frame setjd Checks that setjd will recognize your date format and observatory name to produce a correct Julian date hsp_nd Runs phot at
26. perl version of pgplot PGPLOT This may be done through CPAN as root perl MCPAN e install ExtUtils F77 perl MCPAN e install PGPLOT If you find that when running programs that use pgperl wqplot and wplotlc that you get an error refering to unresolved symbols this can be fixed by editing perl s pgplot makefile This is discussed in the Help file Apparently this occurs because pgperl is not picking up the fact that you are using a f2c based Fortran compiler e g g77 or f2c If you used CPAN pgplot was probably installed in root cpan build PGPLOT 2 20 Change to this directory Then open Makefile PL and change the line use ExtUtils F77 to use ExtU tils F77 qw generic g77 Then run the following perl Makefile PL make make test This should produce nice plots make install 18
27. remove overlapping data especially when that overlapping data is of much poorer quality Weld has the ability to remove parts of the light curves when you create your master light curve The c flag allows you to include a file containing observatory name and dates for where you would like to cut An example of that file would look like cuts dat hawa 4425 4425 9 suho 4444 1 4444 3 meao 4410 2 4410 5 Usage weld list o list lc c cuts dat b The observatory names need to match the same observatory code that whiff uses However if you type hawaii it will match with hawa The times are in MJD 50000 0 This is something that may change in the future so be sure to check the helpfile by typing weld If you decide to create bjed files as well then pound signs are placed in front of those points that you did not want to include The plotting program wplotlc plots your bjed files in different colors Wplotlc knows not to read lines that begin with In this way you can plot up the light curve with those points your selected removed however the information is still in the bjed files in case you want to make small changes manually Usage wplotlc list bjed p 24 where list bjed is a list of bjed files to plot and p specifies the length of each panel on the page in hours 12 6 Advanced Topics 6 1 Reducing 3 channel phototube data Waed now has limited support for reducing three channel phototube data This new feature is still u
28. s the endless variation in formats that different observatories use to denote time and date in their fits headers As a famous astronomer once said if you think this is hard to read spare a thought for those who had to write it 6 4 Editting Wqed config files Waed has two configuration files stored in the directory HOME wet Both files are necessary for calculating barycentric corrections stars dat is a list of the right ascensions and declinations while leapseconds dat is a list of when all leap seconds were applied to UTC The format of stars dat is very simple It consists of 7 columns separated by whitespace The first column is the name of the star all as one word e g PG1351 489 not PG 1351 489 The next 6 columns are the right ascension hours minutes seconds and declination hours minutes and seconds The epoch of the coordinates is J2000 Take care when adding the position of a star that you use this epoch or your corrections will be wrong This is not a fixed format file you can separate different columns by one whitespace character or a hundred However for the sake of neatness we try to keep the columns aligned If you have two or more names that you commonly see for the same star e g PYVul G185 32 or WDJ1937 2743 make a different entry for each name keeping the coordinates the same leapseconds dat is lists the dates of all leapseonds applied to UTC You should not edit this file instead download a new one whe
29. stall or update soft ware These are mac development tools that can be found on the mac web sites If you didn t have X11 installed you may also find that you are missing fortran and a c compiler necessary for wqed Look for gcc and fortran on fink and install these packages A good place to get a lot of as tronomy tools is the Scisoft package http web mac com npirzkal Scisoft Scisoft html It includes such tools as iraf wcstools and pgplot Its version of pgplot is not compiled How ever installing pgplot is easy with fink You must include the unstable tree in fink To do this type fink configure fink selfupdate fink selfupdate cvs fink index fink scanpackages Then to install pgplot run fink install pgplot The pgplot librray and code is then in sw lib pgplot At this point you can use makewqed making the appropriate changes to the directories at the top of the file 3 Tutorial Data reduction proceeds as follows e Extract light curves using Antonio s IRAF routines or your favourite aperture photometry package e Choose the optimal aperture light curve from the output of the previous step e Convert the data to the Wqed format using whiff e Correct the data using Waed e Merge light curves from different runs using weld e Analyze the light curves with your favorite Fourier Transform programs e g period04 or fitle see 4 3 This tutorial assumes that your are using Antonio s routines to extra
30. t curve directly using whiff A1618 0001 fits o mcdo l1 g3829_mcdonal_20071110_12 sec Whiff generates a name for the output file by combining the observatory date and hour of the run For our data taken at McDonald on 2007 11 10 at 03 30 19 UTC the output filename known as the run name will be mcdo071110 03 wq To create a header for data from other telescopes type whiff o to see a list of recognised observatories If your telescope participated in a recent WET run then whiff probably already understands the format of your fits file If not it is easy to configure Whiff to understand a new telescope s fits file See 6 3 3 4 Waqed The purpose of Wqed is to remove atmospheric and instrumental effects from data as well as to remove hopelessly corrupted data from the light curve This is primarily achieved by offering an 4 Antonio s routines automatically create a file called tapered_first_image fits so you know which image was the first processed by hsp_nd interactive way of dividing a lightcurve by one or more reference stars selecting and removing bad points and fitting and removing trends in the data It also calculates the appropriate barycentric corrections and writes that information to the header Waed is an re design of the old DOS program ged written by Ed Nather qed was designed to work with 2 or 3 channel PMT data taken with a specific program called Quilt and started to creak when exposed to data extract
31. t the order of the polynomial to fit 1 for linear 2 for quadratic etc by typing the appropriate number A polynomial will be fit and removed from the data As a rough rule of thumb a second order polynomial should be sufficient for removing the effects of differential extinction 3 4 3 Saving your results When the lightcurve has been edited to your satisfaction it s time to save your work Select the appropriate channel and write the lightcurve to disk by typing W The cursor will change to a vertical bar allowing you to select the region of the lightcurve you want to save To save the entire lightcurve just type E If you try to save separate sections of the lightcurve subsequent sections will be appended to what was previously saved A common request is to save the lightcurves of the target and first reference star Channels 1 and 2 SHIFT W provides a handy shortcut to save both channels at once Wqed saves a file with the extension lc where the question mark is replaced with the channel number The header from the input file is copied to the output file Some keywords are added including two for the barycentric date of the data The keyword Bjed is the Barycentric Julian Ephemeris Date also known as just Barycentric Julian Date of the midpoint of the first exposure BjedCorr is the linear barycentric correction to apply to the times The barycentric date in days of the it exposure T is ti 86400 where Bjed and
32. tion of your pgplot installation Specifically you need the path of the files libpgplot so and libcpgplot so Edit the file Makefile by setting the variable XlibLibrary to the path of libX11 so and the pgInclude variable to the location of pgplot Run make from the command line make all On macs this may be called libX11 dy or somesuch 3On some installations you may find the equally acceptable statically linked libraries with the extension a If you see error messages after this step play with the values of these two variables until you get it to work consulting your local unix guru for help Once Wqed compiles you probably want to put links to Wqed various scripts and binaries in your bin directory so you can easily access run the programs The script installwqed will create soft links into your SHOME bin directory for all the programs in the wqed bin directory If you do not have HOME bin directory create one before running installwqed You do not need root access for this step Installwqed also creates a directory calls SHOME wet and adds some necessary configuration files to it If this directory already exists it updates the configuration files Compiling on a Mac Installation on a Mac has been successfully performed for OS X You will need fink and X11 installed on your mac if not installed you will find them on the disks that come with your Mac Fink requires the most current version of Ctab before it will allow you to in
33. update leapsecond script included with this package Tele McDonal Object G38 29 Date 2007 11 10 08 30 24 0 73838 7 Aad ll pA IN et 61784 2 a cee tien E a a di POO OT Yin year a 14612 3 oe Ne tre oe ae ae ee a if t IS a 58729 0 5000 10 1 5x1 04 extot 2 5x10 3x70 Type for a list of commands Figure 1 Example Wqed startup screen The header tells you the telescope object name and date and time of your first observation The channel numbers referring to the separate columns stars in your input file are found on the right Use these numbers to select each channel star The number on left show the average number of counts in each channel Just like chooselc the Z key allows you to zoom into a certain region of the screen Type Z and the cursor changes from cross hairs to a box Move the mouse to encompass the area you want to zoom into and hit Z again To un zoom type SHIFT Z Note this zooms back a step but does not return to the original zoom level To Un zoom back to the initial screen size type U Points badly affected by cloud or otherwise undesirable can be removed from the lightcurve or garbaged Type G select the region with the bad points and type G again Note that only points from the currently selected channel are removed others are ignored To select all bad points in a given time interval from all channels use SHIFT G Select a region using Ctrl G
34. were introduced For example for data taken on 1999 Jan 1 63 leapseconds were applied instead of 64 This bug is now fixed e When the positions of stars were being read in from stars dat the value of seconds of right ascension was incorrectly set to minutes of right ascension In tests we find this introduced an error in the calculated barycentric date of 0 002 to 0 08 seconds This bug is now fixed e whiff incorrectly extracted dates from fits files for the 30th and 31st December of any given year returning nonsensical results To test our barycentric calculation we compare our result to the JPL DE405 emphemerides as determined by IDL s cmephem package We calculated the barycentric correction for 10 000 randomly chosen ra dec and dates between 1970 and 2030 and compared the result with the http cow physics wisc edu craigm idl ephem html 16 estimate from Wqed s code We currently find a mean discrepancy of 4 6 x 10 but an rms scatter of 0 08 seconds While this is smaller than the typical timing uncertainty due to photometric error it is still larger than we expect and we are investigating its cause Because we do not use the latitude and longitude of the observatory the accuracy of the correction is never any better than 0 02 seconds 6 7 2 Correcting timings of previously reduced data There is no need to re reduce data from the previous version of Wqed Instead use the program waqverify to search for and fix he
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