The new scientific capabilities and GUI facilities are summarized in the Introduction section. Detailed help on various topics can be found by searching the Table of Contents.
Xguiphot is still under development. If you have comments, bug reports, or specific suggestions for improvement please contact the author at davis@noao.edu or the iraf help desk at iraf@noao.edu.
In interactive mode a GUI provides facilities for: selecting and displaying images and object files; creating, viewing and editing object lists; setting, reviewing, editing and saving parameter sets; selecting objects to measure from the image display or the object list using the image cursor, and / or object markers; displaying the results in both text table and graphical form; and browsing the on-line documentation. In non-interactive mode Xguiphot can be driven from an existing object file or from an object list generated at runtime.
For more information on issues that may affect the accuracy of the photometry Consult the Data Requirements section of the IRAF xguiphot help page.
cl> xapphotXguiphot is the only compiled task in the xapphot package. The remaining tasks are parameter set tasks.
xa> help xapphotTo view the help page for a particular task on the terminal type phelp followed by the task name as shown below.
xa> phelp xguiphotHelp text, in this case the xguiphot tutorial, can also be piped to the local printer as shown below
xa> help xgtutor1 | lprint xa> help xgtutor2 | lprintThe on-line GUI documentation can be found in the HTML document xapphot$doc/xguiphot.html. This document can be viewed and printed with any standard web browser.
xa> epar xguiphotTo edit an Xguiphot parameter move the cursor to the line specifying the desired parameter name, enter the new value followed by a carriage return. When editing is complete type ":wq" to exit the epar task and update the parameters. Techniques for editing the impars, dispars, findpars, omarkpars, cenpars, skypars, photpars, cplotpars, and splotpars parameter set parameters are described in the Editing the Xguiphot Parameter Sets section.
xa> type imlist m51b m51v m51rThe default value of images is "*" which will select all images of any type in the current directory. Images may include a directory specification, e.g. "may31/*" or "mydata$*.fits", where mydata$ is an IRAF environment variable defined by the user specifying the desired path name.
The root image name, i.e. the image name stripped of directory and section information, is used to set up the default input object and output results file naming conventions. For example the root image name for the image file /u2/davis/m51b.imh[200:400,200:400] is "m51b.imh" so by default Xguiphot will search for an objects file called "m51b.imh.obj.#" and create an output file called "m51b.imh.mag.#" where "#" is latest and next available version number respectively.
Xguiphot can analyze images in multi-extension files, e.g. m51b.fits[3] specifies the image in the third extension of the FITS file m51b.fits and m51b.hhh[2/4] specifies the second image in the four image GEIS file m51b.hhh. In the latter two cases the root image names are "m51b.fits3" and "m51b.hhh2" respectively. The square brackets around the extension numbers are removed to avoid problems with special characters in file names.
In general users should try and keep their image names as short as possible. Although this is not always convenient they should also, if possible, avoid appending the ".imh", ".hhh", or ".fits" extensions to their input image names, as these extensions automatically become part of the default input and output file names.
xa> type objlist m51bxy m51vxy m51rxyBy default Xguiphot attempts to match the input images and objects files one to one. If the number of objects files is greater than zero but less than the number of images then the last objects file will be used for all the "extra" images. In interactive mode the user can override the default image and object file matching behavior.
Xguiphot supports a default input file name convention. If objects is "default", then for each image Xguiphot searches for a file called "root.obj.version", where root is the root image name described above, "obj" is extension identifying the file as an objects file, and version is the latest version, e.g. "m51b.obj.2" or "m51b.fits.obj.3".
The simplest object file is a text file containing the x and y coordinates of the objects to be measured, one object per line with the x and y coordinates in columns one and two respectively. A portion of a simple object file is shown below.
xa> type objfile 31.23 80.61 102.42 305.73 518.11 1021.89Xguiphot also supports a more complex objects file format capable of describing circular, elliptical, rectangular, and polygonal object and sky apertures, and either concentric or offset sky apertures. Detailed information about the object file format can be found in the Objects File Format section of the appendices. A portion of a more complex objects file is shown below.
507.000 445.000 442.482 409.575 circle 9.59 ; circle 17.10 23.69 266.589 60.769 ellipse 18.69 0.4706 0.0 ; ellipse 24.91 31.56 0.4706 0.0 258.633 259.180 ellipse 65.06 0.8243 29.465 ; 442.482 460.780 rectangle 0.00 47 .14 0.6940 3.877
If the object or sky geometry is absent or undefined, i.e. equal to INDEF in the input objects file, then the default object and sky geometries are defined by the default values in the photpars and skypars parameter sets.
cl> type maglist m51bmag m51vmag m51rmagBy default Xguiphot attempts to match the input images and results files one to one. If the number of results files is greater than zero but less than the number of images then the last results file will contain the results for all the "extra" images in addition to the results for the one it matches. In interactive mode the user can override the default image and results file matching behavior.
Xguiphot supports a default output file name convention. If results is "default", then for each input image, Xguiphot creates a file called "root.mag.version", where root is the root image name described above, "mag" is an extension identifying the file as a results file, and version is the next available version number, e.g. "m51b.mag.1" or "m51b.fits.mag.2".
xa> epar impars xa> imparsParameter sets can also be edited from within the main task editor. To edit the impars parameter set while editing the Xguiphot task parameters type "epar xguiphot". Move the cursor to the impars line and type ":e". The menu for impars will appear ready for editing. Edit the parameters and type ":wq" to quit and update the impars parameters. Epar will return to the Xguiphot parameter menu after which other parameter sets or task parameters can be edited.
If the guifile is undefined the user can still run Xguiphot interactively. However only keystroke and colon commands will be available, only a single graphics window will be available for displaying the image, the object and sky regions, and the results, and certain functions like windowing the image display will be unavailable. This mode of running Xguiphot is not discussed in this document. More information about it can be found in the regular Xguiphot help page.
Since the GUI file is a text file which is read at runtime, an individual user or site can customize the GUI to local taste. The default GUI is stored in the file "xapphot$gui/xguiphot.gui".
xa> cd [mydir] xa> xguiphot List of images to be analyzed (*): List of input objects files (default): List of output results files (default):After a few seconds the xguiphot control panel activates, the first image is displayed in the image display window, the image display cursor activates, and Xguiphot is ready to accept user commands.
If an error condition is detected when Xguiphot starts up a warning message will be displayed in the status line at the bottom of the image display window.
The text displayed in the help panel is part of the HTML document xapphot$doc/xguiphot.html, which can be browsed while Xguiphot is running or viewed and printed off-line with your standard web browser.
To display the current directory and subdirectory structure bring up the files panel using the files menu as shown below.
To set a new current directory using the Files panel:
To display the current image file directory bring up the files panel using the files menu as shown below.
To enter a new images file directory using the Files panel:
To display the current image file directory using the Files panel and Files menu as shown below.
To quickly display the current image template, image name, and image sequence number without using the Files panel use the builtin colon commands as shown below.
To quickly define a new image template and load a new image list without bringing up the Files panel using the builtin colon commands.
To select a new image using the Files panel:
To quickly change images using the builtin colon commands:
To move backwards and forwards sequentially in the image list without bringing up the Files panel:
To browse the image headers use the image header panel Next and Prev buttons.
The image header browsing facilities can be used to check whether critical keywords defining the gain, readout noise, exposure time, filter, airmass, and time of the observation are present and correct in the image headers, and whether these keywords match the expected keywords defined by the impars parameters ikgain, ikreadnoise, ikexptime, ikairmass, ikfilter, and ikobstime. Missing keywords will generate an error message in the status line at the bottom of the image display window.
To pan the image:
To zoom the image display:
To window the image display:
To use the builtin task specific keystroke commands:
To access the image display menu:
To edit the dispars parameters using the dispars parameter editing panel:
To compute and print the model fit parameters using the image display menu and / or a keystroke command:
To compute, plot and print the model fit using the Model fitting panel:
To store the new value of the hwhm in impars parameter ihwhmpsf using the Model fitting panel.
Most users should set the impars parameters ihwhmpsf, imindata, imaxdata, ikreadnoise, ikgain, and ikexptime parameters to values appropriate for their entire data set. The ikairmass, ikfilter, and ikobstime keywords should be set if the user plans to do photometric calibrations of the measurements. The remaining parameters can normally be left at their default values.
To edit the impars parameters using the impars parameter editing panel:
To edit an impars parameter without bringing up the impars parameter editing panel, type in the appropriate colon command as shown below for the case of the impars imaxdata parameter.
Users can check that Xguiphot is reading in correct values for the keywords ikgain, ikreadnoise, ikexptime, ikairmass, ikfilter, and ikobstime from the image header by displaying both the image header panel and the impars parameter editing panel as they browse the image list. If the header keywords are read in correctly the correct values of gain, readout noise, exposure time, airmass, filter id, and time of observation should appear opposite the igain, ireadnoise, ietime, iairmass, ifilter, and iotime impars parameters in the parameter editing panel.
To display the current objects file file directory activate the Files panel using the Files menu as shown below.
To enter a new objects file directory using the Files panel:
To display the current objects file directory bring up the Files panel using the Files menu as shown below.
To display the current objects file template, objects file name, and objects file sequence number without bringing up the Files panel use the builtin colon commands as shown below.
To enter a new objects file template using the Files panel:
To define a new objects file template and load a new objects file list without bringing up the files panel use the builtin colon commands as shown below.
To select a new current objects file using the Files panel:
The same operation can be performed using the builtin colon commands as shown below:
To move backwards and forwards sequentially in the objects file list without bringing up the Files panel:
To create an objects list from the current objects file using the List menu:
To perform the same functions using the List panel:
To perform the same functions using the builtin cursor keystroke commands:
To create an object list for an image using the List menu:
To perform the same functions using the List panel:
To perform the same functions using the builtin cursor keystroke commands:
To edit the findpars parameters using the findpars parameter editing panel:
To edit a findpars parameter without bringing up the findpars parameter editing panel type in the appropriate colon command as shown below for the case of the findpars fthreshold parameter.
The four supported object record types are listed below. The most common record types are object and object plus annular sky.
Six object and sky geometries are supported.
Xguiphot prompts for different quantities for the different geometries, i.e. radii only for circles, semi-major and minor axes and position angle for ellipses, etc.
The following example shows how to create a simple object list consisting of a set of identical circular object and circular annular sky region records.
Note that in both cases the "Draw list ..." menu item can be replaced with the keystroke commands z followed by a.
To view the objects list using the List panel:
To overlay the object list on the image display using the List menu:
To perform the same operation with the builtin keystroke commands:
To edit the omarkpars parameters using the omarkpars parameter editing panel:
To edit an omarkpars parameters without bringing up the omarkpars parameter editing panel type in the appropriate colon command, as shown below for the case of the omarkpars otolerance and ocharmark parameters.
The same function can be performed using the Edit menu as shown below.
If the object list marker is active, users can also select the "Next object" item from the object list marker menu by pressing the right mouse button inside the object list marker, or by typing the f keystroke command inside the object list marker. To browse the object list randomly or locate a specific object in the object list on the image display using the List panel:
To browse the object list randomly or to locate a specific object in the object list using the image display and image display menu:
To perform the same functions using the image cursor and image display menu.
If the object list marker is active then the current object can be deleted or undeleted by pressing the right mouse button inside the object marker and selecting the "Delete current object" or "Undelete current object" items, or by typing the d and u keys inside the object marker.
The object and sky position and geometries can also be added to the objects list by typing them into "Enter object geometry" entry box and hitting the Enter button. The required object formats are described in the Objects File Format section of the appendices. For small numbers of objects the model fitting code described in the Estimating the Hwhm of the Psf section can be used to determine good values for the x and y coordinates, axis ratios, and position angles.
The photometry marker can also be used to add objects to an existing list as described in the Creating Object Lists with Markers section.
To save the objects list to a file using the builtin colon commands:
To display the current results file directory bring up the Files panel using the Files menu as shown below.
To enter a new results file directory using the Files panel:
To display the current results file template using the Files panel and files menu;
To display the current results file template, results file name, and results file sequence number using the the builtin colon commands:
To enter a new results file template using the Files panel:
To define a new results file template using the builtin colon commands:
Users can check or change the results file logging status using the Files menu, the Files panel, the Files marker and Files marker menu, the "Logresults" command buttons in the List panel, the Photometry table panel, the Photometry plots panel, or by typing the ":logresults" colon command in the image display window.
For example to enable / disable results file logging:
or
Users should review the recentering algorithm parameter calgorithm The most useful options are "none" which disables recentering, and and the default value "centroid1d".
Users check the values of cradius and set it to a reasonable value, usually something like 2-3 times the hwhm of the psf, but never less than 2.5 pixels.
By default center marking is disabled (ctrmark is "no"), while object and sky marking is enabled. In crowded regions users may wish to turn on center marking, and disable object and sky aperture marking, in order to avoid drawing a lot of confusing graphics on the image display.
To edit the cenpars parameters using the cenpars parameter editing panel as follows:
To edit a cenpars parameter by typing in the appropriate colon command follow the example shown below for the cradius and ctrmark parameters.
Users should check and set the sky geometry parameters smode, sgeometry, srannulus, swannulus, saxratio, and sposangle. For bright stellar objects mode is usually "concentric", srannulus is usually ~10 * hwhm of the psf and swannulus is 5-10 pixels.
Users should check the sky fitting algorithm parameter salgorithm. The most useful options are usually "constant", "mean", "median", "mode32", and "hcentroid". The remaining algorithm parameters should normally be left at their default values.
By default sky aperture marking is enabled (skymark is "yes"), and the default sky aperture marking color is different from the photometry aperture marking color. Users should normally leave sky marking enabled if they are measuring objects interactively, and disable it if they are measuring large numbers of objects automatically.
To edit the skypars parameters using the skypars parameter editing panel:
To edit a skypars parameter by typing in the appropriate colon command follow the example shown below for the srannulus, swannulus and skymark parameters.
Users should check and set the object geometry parameters pgeometry, papertures, paxratio, and pposangle. Multiple apertures lists or ranges may be specified as follows, i.e. papertures = "3,5,7,10,15" or "1:15:1.0"
Users may also wish to change the default value of the magnitude zero point pzmag. The most useful choices are 0.0 and 25. The former value provides a direct conversion to flux, and the latter value agrees with the task defaults in the digiphot package and the imexamine task (except for the effects of exposure time normalization).
By default photometry aperture marking enabled (photmark is "yes"), and the default photometry aperture marking color is different from the sky aperture marking color. Users should leave photometry aperture marking enabled if they are measuring objects interactively, and disable it if they are measuring a large number of objects automatically.
To edit the photpars parameters using the photpars parameter editing panel:
To edit a photpars parameter by typing in the appropriate colon command as shown below for the case of the photpars papertures, and photmark parameters:
To measure an object using the image display menu:
By default the object and sky apertures are marked on the image display in different colors, and quick-look results are printed in the status line in the following format.
If either the photometry or sky aperture geometry parameters, pgeometry or sgeometry are "polygon" the user must define the polygonal apertures interactively before doing photometry. This is done by using either the "Mark polygons ..." item in the Phot menu or the v keystroke command in the image display window. In either case the user must mark the vertices of the desired polygon by moving to each vertex in order and typing v to mark the vertex, followed by the q keystroke to quit the polygon marking menu. Xguiphot will automatically close the polygon. The user can redefine the polygon at any time. Xguiphot will use the stored aperture only when the pgeometry parameter is set to "polygon". If the value of the smode parameter is "concentric" and the sky geometry is "polygon", then Xguiphot will construct an annular polygonal sky region using the object polygon and the values of the srannulus and swannulus parameters to define a polygonal sky annulus. If the sky fitting mode is "offset" then the user is prompted for and must draw a separate sky polygon, which will be annular or filled depending on the value of swannulus.
To measure an object using the default photometry marker and mouse:
Users should be aware that measuring an object through the default photometry marker is not quite that same as point at it with the mouse and typing Spacebar, because in the former case the measurement geometry is read from the marker itself, and in the latter case it is read from the photpars and skypars parameter sets. Due to the finite precision of the image display window these two geometries will not exactly equal.
To redefine the measurement apertures interactively and do the measurement through the photometry marker in "concentric" sky mode:
The default sky fitting mode can be changed quickly from "concentric" to "offset" by:
A list of objects can be saved for later measurement by repeating any of the above recipes and selecting the "Save to objects list" item from the Photometry marker menu, instead of the "Measure" item.
Each time the photometry marker is dismissed and reactivated it is redrawn using the default object and sky geometries specified in the skypars and photpars parameters, and any user changes are lost. To make the current photometry marker geometry the default geometry:
After each measurement the object and sky apertures will be marked on the image display in different colors, and the quick-look results will be printed in the status line in the following format.
To find and measure objects automatically using the Phot menu:
or alternatively type the keystroke command * in the image display window.
By default the sky and photometry apertures will be marked on the image display as the objects are detected and measured. In crowded fields users may wish to disable the object and sky marking options, and enable the center marking option instead. When the measurements are complete a message stating the number of detected objects will appear in the status line.
To measure the objects in the list sequentially using the Phot menu:
To select and measure objects in the objects list using the List panel:
The function of the objects list panel Next, Prev, Restof, and All commands buttons are duplicated by the o, -, +, and # keystroke commands executed in the image display window. The list object nearest the image cursor can be selected and measured using the . keystroke command.
To select and measure the list object nearest the image cursor using the image display menu:
The status line cn be cleared by selecting the "Clear status line" item from the Results menu or by typing the ; keystroke command in the image display window.
If several objects in the object list are measured with a single command, then only the results of last measurement are printed in the status line.
The results of the automatic detection and measuring command are not printed to the status line. Instead a message stating the number of object that were detected and measured is printed. The last measurement may still be recalled and printed as described above.
To disable sky and photometry aperture marking and enable center marking instead using the Results menu:
If the object list is detected and measured automatically, then the initial object list centers are also marked if the omarkpars parameter objmark is enabled.
If the table is enabled when a measurement is made then the following quantities are printed to the table where they can be examined.
The quick-look table is photometry table is most useful for making comparative measurements, e.g. repeated measurements of the same object with different parameter settings, or repeated measurements of the same object taken at different times, in different observing conditions, etc.
For reasons of efficiency it is a good idea to disable the quick-look table when making measurements of large numbers of objects simultaneously, and to clear the table using the Clear button when it becomes too large.
If the plotting panel is enabled when a measurement is made then the following quantities are displayed by default in the plots panel:
Each plot has an associated Activate button. Pressing the Activate button activates IRAF cursor mode; pressing the Deactivate button deactivates it. In cursor mode the user can select different plots with the associated menu button; and use the builtin IRAF cursor mode keystroke commands to display the plot in various ways.
The multi-aperture analysis includes the following quantities:
The quick-look photometry plots panel is most useful for examining the object and sky region in detail as measurements are made, for examining the often critical sky measurements more closely, and for examining the results of any multi-aperture analysis.
For reasons of efficiency it is a good idea to disable the quick-look photometry plots panel when making measurements of large numbers of objects simultaneously.
To select an item from one of the the main menus:
The function of a menu item preceded by a characters, e.g. item
n | Next imagein the Files menu, can be duplicated by typing the character, i.e. the character n in the preceding example, in the image display window.
Menu items with trailing periods, e.g. item
| Help ...in the Files menu, either bring up a new panel or demand further action from the user. Menu items with a trailing solid right caret, e.g. item
Edit >in the Psets menu bring up a submenu.
The 2 main command buttons are: the Help button and the Quit button.
To use activate a command button:
$ | Files panel ... # Activate the files panel n | Next image # Select next image p | Previous image # Select previous image ] | Next objects file # Select next objects file [ | Previous objects file # Select previous objects file | Enable / Disable file logging # Toggle output file logging | Help ... # Display help for files menu
More on selecting files can be found in the Setting the Image Directory, Setting the Image Template, Browsing the Image List, Browsing the Image Headers, Setting the Objects File Directory, Setting the Objects File Template, Browsing the Objects File List, Setting the Results File Directory, Setting the Output File Template, and Logging the Results sections.
n | Next image # Display next image p | Previous image # Display previous image | Dispars pset ... # Activate dispars pset editing panel i | Current image # Redisplay current image | Impars pset ... # Activate impars pset editing panel h | Display header ... # Toggle image header display panel x | Compute model fit ... # Print model fit results y | Show model fit ... # Toggle model fit display panel | Options > # Display options submenu | Help ... # Display help for images menu
The options sub-menu contains the following choices.
Show / Dismiss crosshair # Toggle crosshair cursor
Dismiss / Showfiles marker # Toggle files marker
Dismiss / Show coords marker # Toggle coords marker
Clear status line # Erase status line
Further information on browsing images and image headers can be found in the Browsing the Image List, Setting the Impars Parameters, and Browsing the Image Headers sections
Further information on interacting with the image display window and changing the default image display parameters can be found the sections on Setting the Dispars Parameters and Interacting with the Image Display.
Information on modeling objects and determining a good value for the impars ihwhmpsf parameter can be found in the section Estimating the Hwhm of the Psf.
More about the crosshair cursor, files marker, coordinates marker, and status line can be found in the Image Display Cursor, the Files Marker, the Coordinates Marker, and the Status Line sections.
l | List panel ... Activate the list editing and viewing panel ] | Next file Select the next input objects file [ | Previous file Select the previous input objects file r | Current file Reread the current objects file | Impars pset ... Activate the impars pset editing panel | Findpars pset ... Activate the findpars pset editing panel @ | Find list Find objects and write to list | Draw list ... Activate the list drawing code | Omarkpars pset ... Activate the omarkpars pset editing panel m | Mark list Mark list on the image display e | Erase list Erase marked list from the image display e | Help ... Display help for the lists menuFurther information on creating object lists can be found in the Creating Objects Lists from Object Files, Creating Objects Lists Automatically, Setting the Findpars Parameters, Creating Objects Lists with the Image Cursor, and. Creating Objects Lists with the Photometry Marker sections.
More information on overlaying the object list on the image display can be found in the Viewing the Image List, and Setting the Omarkpars Parameters sections.
l | List panel ... Activate the list viewing and editing panel | Show object marker Show / dismiss the object marker ^ | Rewind list Rewind the objects list f | Next object Select next object in list b | Previous object Select previous object in list ~ | Nearest object ... Select list object nearest cursor a | Add object(s) ... Add objects to list graphically d | Delete object(s) ... Delete objects from the list u | Undelete object(s) ... Undelete deleted list objects z | Delete list Delete entire list | Help ... Display help for lists menu
Further information on browsing, viewing, and editing objects lists can be found in the Browsing the Objects List, Deleting and Undeleting Objects from the Objects List, Adding Objects to the Objects List, and Saving Objects Lists ti Objects Files, sections.
| Impars pset ... # Activate impars pset editing panel | Cenpars pset ... # Activate cenpars pset editing panel | Skypars pset ... # Activate skypars pset editing panel | Photpars pset ... # Activate photometry parameters editing panel v | Draw polygons ... # Draw object or object / sky polygons Sp | Point and measure ... # Measure object(s) nearest the cursor | Findpars pset ... # Activate detection parameters editing panel * | Find and measure # Find and measure objects automatically # | Measure list # Measure existing object list l | List panel ... # Activate list panel | Show/Dismiss object marker # Show / Dismiss object list marker ^ | Rewind list # Rewind objects list o | Measure next # Measure next in list + | Measure rest of # Measure rest of list - | Measure previous # Measure previous in list . | Measure nearest # Measure nearest in list | Help ... # Display help for phot menu
More information on setting the algorithm parameters can be found in the Setting the Impars Parameters, Setting the Cenpars Parameters, Setting the Skypars Parameters, and Setting the Photpars Parameters sections.
More on the various modes of making photometry measurements can be found in the Measuring Objects with the Image Cursor, Measuring Objects Through the Photometry Marker, Detecting and Measuring Objects Automatically, Measuring Objects in the Objects List, and Measuring Objects Through the Object List Marker sections.
| Enable / Disable logging # Toggle results file logging CR | Clear status line # Clear status line ; | Display last result # Display last result | Enable / Disable ctrmark # Toggle object center marking | Disable / Enable skymark # Toggle sky aperture marking | Disable / Enable photmark # Toggle photometry aperture marking t | Photometry table ... # Display the photometry table panel g | Photometry plots ... # Display the photometry plots panel | Cplotpars ... # Activate cplotpars pset editing panel | Splotpars ... # Activate splotpars pset editing panel | Help ... # Display help for results menu
More on view the results can be found in the The Status Line, The Graphics Overlay, The Quick-Look Photometry Table, andThe Quick-Look Photometry Plots sections.
Edit # Edit the selected psets
Apply # Apply parameter changes to selected psets
Cancel # Cancel parameter changes to selected psets
Unlearn # Return selected psets to their default state
Update # Update selected psets on disk
Dismiss # Dismiss selected pset editing panels
Help # Display help for psets menu
Each menu item above is actually a submenu of the following form:
All
Impars
Dispars
Findpars
Omarkpars
Cenpars
Skypars
Photpars
Cplotpars
Splotpars
More about parameter editing using the parameter editing panel can be found in the The Parameter Set Editing Panel section. The equivalent colon commands are listed in the Colon Commands section.
Information about setting the parameters to their optimal values can be found in the in the Setting the Impars Parameters, in the Setting the Dispars Parameters, in the Setting the Findpars Parameters, in the Setting the Omarkpars Parameters, Setting the Cenpars Parameters, Setting the Skypars Parameters, and Setting the Photpars Parameters sections. sections.
When the image display cursor activates, the image display window is ready to accept user commands in the form of mouse clicks, task specific keystroke commands, IRAF builtin keystroke commands, task specific colon commands, and IRAF builtin colon commands.
To move the files marker:
Enable / Disable logging # Enable / Disable results logging
Help ... # Display help for files marker
Dismiss marker # Delete the files marker
To delete the files marker:
To reactivate the files marker:
For more on displaying the current input and output file names using the Files panel or colon commands see the Setting the Image Template, Setting the Objects Files Template, and Setting the Results Files Template sections.
To move the coordinates marker around:
Help ... # Display help for coordinates marker
Dismiss marker # Delete the coordinates marker
To delete the coordinates marker:
To reactivate the coordinates marker:
To erase the status line:
To recall the last photometric measurement to the status line:
To input a colon command from the status line:
In some cases a crosshair cursor can be more useful that the default circle. To change the default image display cursor from a circle to a crosshair:
To track the cursor coordinates in image pixel units
To print the current position of the image display cursor in the status line:
To window the image display:
To return to the default zoom:
To activate the image display menu:
Sp | Point and measure # Measure object nearest the cursor . | Measure nearest in list # Measure list object nearest the cursor ~ | Find nearest in list # Locate list object nearest the cursor d | Delete nearest in list # Delete list object nearest the cursor u | Undelete nearest in list # Undelete list object nearest the cursor | Show / Dismiss phot marker # Activate / deactivate the phot marker | Align / Offset photsky marker # Align / offset the photsky marker | Set offset / concentric sky # Toggle the sky fitting mode x | Compute model fit # Fit gaussian to nearest object y | Show / Dismiss model plot ... # Toggle model fit plottingNote that most of these commands use the current cursor position as an initial position in some way, e.g. the measure, list editing, and model fit commands use the the cursor x and y position as an initial position. The photometry marker commands activate or move the marker to the position of the cursor.
For more about selecting and measuring objects with the cursor go to the Measuring Objects with the Image Cursor and Measuring Objects in the Objects List sections.
For more about locating objects in the objects list and deleting or undeleting objects from the objects list go to the Browsing the Objects List and Deleting and Undeleting Objects from the Objects List sections.
For more about creating and manipulating the photometry marker go to the The Photometry Marker section. For information on using the photometry marker to create objects lists see the Creating Objects Lists with the Photometry Marker and Adding Objects to the Objects List sections.
For information on how to use the photometry marker to make quick-look measurements go to the Measuring Objects Through the Photometry Marker section.
General commands
? Toggle help panel Q Quit task
$ Toggle files panel : Colon command
CR Erase status line
Image display commands
i Redisplay current image h Toggle image header panel
n Display next image p Display previous image
x Model nearest object \X Refit previous object
y Toggle model fitting panel
Object list creation and display Commands
l Toggle objects list panel r Reread current objects file
] Read next objects file [ Read previous objects file
@ Autofind objects list z,a Draw objects list
m Mark objects list e Erase objects list
Object list editing commands
^ Rewind object list ~ Move to nearest list object
f Move to next list object b Move to previous list object
z Delete entire objects list d Delete nearest list object
u Undelete nearest list object a Add object to list
Object measurement commands
SP Measure nearest object v Draw object and sky polygons
* Find and measure objects # Measure object list
o Measure next list object - Measure previous list object
+ Measure rest of list . Measure nearest list object
Results display commands
t Toggle tables panel
g Toggle plots panel G Replot
CR Erase status line ; Display last measurement
A Draw and label axes B Backup over last instruction
C Print the cursor position D Draw a line segment
E Expand the plot F Set fast cursor
H Step cursor left J Step cursor down
K Step cursor up J Step cursor right
M Pan P Zoom out
R Redraw T Draw text at cursor
U Undo last edit V Set slow cursor
W Set wcs at cursor X Zoom in in x
Y Zoom in in y Z Zoom in
< Set lower limit of plot to y > Set upper limit of plot to y
\ Escape next character :. Cursor mode colon command
= Draw a plot 0 Reset and redraw
Users should be aware that not all the keys are yet fully functional for
the image display window and the zoomed up image displays of the object
and sky region in the photometry plots panel. In particular it is not yet
possible to produce hardcopies of the image display with the = keystroke.
File Management Colon Commands
:images [template] Show / Set a new image template
:objects [template] Show / Set a new objects file template
:results [template] Show / Set a new results file template
:robjects [template] Show / Set a new output objects file template
:imname [name] Show / Select the current image
:olname [name] Show / Select the current objects file
:rlname Show the current results file
:glname Show the current output objects file
:imnumber [number] Show / Select the current image number
:olnumber [number] Show / Select the current objects file number
:rlname Show the current results file number
:glname Show the current output objects file number
:logresults [yes/no] Log the results to the results file ?
Object List Management Commands
:oselect number Select the current object
:odelete number Delete the current object
:oundelete number Undelete the current object
:oadd geometry Add object to object list
:osave file Save current object list to objects file
Impars Parameter Colon Commands
:iscale [value] Show / Set the image scale
:ihwhmpsf [value] Show / Set the hwhm of the psf
:iemission [yes/no] Show / Set emission features switch
:iskysigma [value] Show / Set the sigma of the background
:imindata [value] Show / Set the minimum good data value
:imaxdata [value] Show / Set the maximum good data value
:inoisemodel [name] Show / Set the noise model
:ikgain [value] Show / Set the CCD gain keyword
:ikreadnoise [value] Show / Set the CCD readout noise keyword
:igain [value] Show / Set the CCD gain in e-/ADU
:ireadnoise [value] Show / Set the CCD readout noise in e-
:ikexptime [value] Show / Set the exposure time keyword
:ikairmass [value] Show / Set the airmass keyword
:ikfilter [value] Show / Set the ifilter id keyword
:ikobstime [value] Show / Set the time of observation keyword
:ietime [value] Show / Set the exposure time
:iairmass [value] Show / Set the airmass value
:ifilter [value] Show / Set the ifilter id
:iotime [value] Show / Set the time of observation
*Permitted values of inoisemodel are: "poisson".
Dispars Parameter Colon Commands
:derase [yes/no] Show / Set the erase status
:dfill [yes/no] Show / Set the fill status
:dxviewport [value] Show / Set the x viewport
:dyviewport [value] Show / Set the y viewport
:dxmag [value] Show / Set the x magnification
:dymag [value] Show / Set the y magnification
:dztransform [name] Show / Set the intensity transform
:dzlimits [name] Show / Set the intensity limits algorithm
:dzcontrast [value] Show / Set the intensity contrast
:dznsample [value] Show / Set the number of sample lines
:dz1 [value] Show / Set the minimum intensity level
:dz2 [value] Show / Set the maximum intensity level
:dlutfile [value] Show / Set the user lookup table file
:drepeat [yes/no] Show / Set repeat status
*Permitted values of dztransform are: "linear", "log", and "none".
*Permitted values of dzlimits are: "median", "image", and "user".
Findpars Parameter Colon commands
:fthreshold [value] Show / Set the detection threshold
:fradius [value] Show / Set the fitting radius
:fsepmin [value] Show / Set the minimum separation
:froundlo [value] Show / Set the lower ellipticity limit
:froundhi [value] Show / Set the upper ellipticity limit
:fsharplo [value] Show / Set the lower sharpness limit
:fsharphi [value] Show / Set the upper sharpness limit
Omarkpars Parameter Colon Commands
:objmark [yes/no] Show / Set the object marking switch
:otolerance [value] Show / Set the object matching tolerance
:ocharmark [value] Show / Set the object marking parameter
:onumber [yes/no] Show / Set the object numbering switch
:opcolormark [value] Show / Set the object mark color
:oscolormark [value] Show / Set the sky mark color
:osizemark [value] Show / Set the mark size
*Permitted values of ocharmark are: "point", "box", "cross", "plus",
"circle", "diamond", and "shape".
*Permitted values of opcolormark and oscolormark are: "red", "blue",
"green", and "yellow".
Cenpars Parameter Colon Commands
:calgorithm [value] Show / Set the centering algorithm
:cradius [value] Show / Set the centering radius
:cthreshold [value] Show / Set the centering threshold
:cminsnrati [value] Show / Set the minimum signal-to-noise ratio
:cmaxiter [value] Show / Set the maximum number of iterations
:cxyshift [value] Show / Set the maximum x or y coordinate shift
:ctrmark [yes/no] Show / Set the center marking switch
:ccharmark [value] Show / Set the center marking character
:ccolormark [value] Show / Set the center mark color
:csizemark [value] Show / Set the center mark size
*Permitted values of calgorithm are: "none", "centroid1d", "gauss1d",
and "ofilter1d".
*Permitted values of ccharmark are: "point", "box", "cross", "plus",
"circle", and "diamond".
*Permitted values of ccolormark are: "red", "blue", "green" and
"yellow".
Skypars Parameter Colon Commands
:smode [value] Show / Set the sky fitting mode
:sgeometry [value] Show / Set the sky fitting geometry
:srannulus [value] Show / Set the inner radius of sky annulus
:saxratio [value] Show / Set the sky annulus axis ratio
:sposangle [value] Show / Set the sky annulus p.a. in degrees
:salgorithm [value] Show / Set the sky fitting algorithm
:sconstant [value] Show / Set the constant for constant sky fitting
:shwidth [value] Show / Set the half-width of histogram in sigma
:shbinsize [value] Show / Set the resolution of histogram in sigma
:shsmooth [yes/no] Show / Set the histogram smoothing switch
:smaxiter [value] Show / Set the max number of fitting iterations
:sloclip [value] Show / Set the lower clipping factor in %
:shiclip [value] Show / Set the upper clipping factor in %
:snreject [value] Show / Set the max number of rejection iterations
:sloreject [value] Show / Set the lower k-sigma rejection limit
:shireject [value] Show / Set the upper k-sigma rejection limit
:srgrow [value] Show / Set the region growing radius
:skymark [yes/no] Show / Set the sky marking switch
:scolormark [value] Show / Set the sky aperture mark color
*Permitted values of smode are: "concentric" and "offset".
*Permitted values of sgeometry are: "circle", "ellipse", "rectangle",
and "polygon".
*Permitted values of salgorithm are: "zero", "constant", "mean",
"median", "mode32", "hcentroid", "hgauss", "hofilter", "hcrosscor".
*Permitted values of scolormark are: "read", "blue", "green", and
"yellow".
Photpars Parameter Colon Commands
:pgeometry [value] Show / Set the photometry aperture geometry
:papertures [value] Show / Set the photometry apertures
:paxratio [value] Show / Set the photometry aperture axis ratio
:pposangle [value] Show / Set the aperture position angle in degrees
:pzmag [value] Show / Set the photometry zero point
:photmark [yes/no] Show / Set the photometry aperture marking switch
:pcolormark [value] Show / Set the photometry aperture mark color
*Permitted values of pgeometry are: "circle", "ellipse", "rectangle",
and "polygon".
*Permitted values of pcolormark are: "red", "blue", "green", and
"yellow".
Cplotpars Parameter Colon Commands
:enx [value] Show / Set number of columns to be contoured
:eny [value] Show / Set number of lines to be contoured
:ez1 [value] Show / Set minimum greylevel to be contoured
:ez2 [value] Show / Set maximum greylevel to be contoured
:ez0 [value] Show / Set the greylevel of the zero contour
:encontours [value] Show / Set the number of contours to be plotted
:edz [value] Show / Set the contour greylevel interval
:ehilomark [value] Show / Set the high / low contour marking option
:edashpat [value] Show / Set the bit pattern for drawing lines
:elabel [yes/no] Show / Set the major contours labeling switch
:ebox [yes/no] Show / Set the box drawing switch
:eticklabel [yes/no] Show / Set the tick mark labeling switch
:exmajor [value] Show / Set the number of major x axis divisions
:exminor [value] Show / Set the number of minor x axis divisions
:eymajor [value] Show / Set the number of major y axis divisions
:eyminor [value] Show / Set the numver of minor y axis divisions
:eround [yes/no] Show / Set the axis rounding switch
:efill [yes/no] Show / Set viewport filling switch
*Permitted values of ehilomark: "none", "hilo", and "pixel".
Splotpars Parameter Colon Commands
:anx [value] Show / Set number of columns to be plotted
:any [value] Show / Set number of lines to be plotted
:az1 [value] Show / Set minimum greylevel to be plotted
:az2 [value] Show / Set maximum greylevel to be plotted
:alabel [yes/no] Show / Set the axes drawing switch
:angv [value] Show / Set the vertical viewing angle
:angh [value] Show / Set the horizontal viewing angle
:.axes[+-] Draw axes of viewport whenever screen is redrawn :.case[+-] Enable case sensitivity for keystrokes :.clear Clear alpha memory (e.g, this text) :.cursor n Select cursor :.gflush Flush plotter output :.help Print help text for cursor mode :.init Initialize the graphics system :.markcur[+-] Mark cursor position after each cursor read :.off [keys] Disable selected cursor mode keys :.on [keys] Enable selected cursor mode keys :.page[+-] Enable screen clear before printing help text :.read file Fill frame buffer from a file :.show Print cursor mode and graphics kernel status :.snap [device] Make hardcopy of graphics display :.txqual qual Set character generator quality (normal,l,m,h) :.txset format Set text drawing parameters (size,up,hj,vj,etc) :.xres=value Set X resolution (stdgraph only) :.yres=value Set Y resolution (stdgraph only) :.viewport x1 x2 y1 y2 Set workstation viewport in world coordinates :.write[!][+] file Save frame buffer in a spool file :.zero Set viewport and redraw frameUsers should be aware that not all the commands are yet fully functional for the image display window and the zoomed up image displays of the object and sky region in the photometry plots panel. In particular it is not yet possible to produce hardcopies of the image display with the :.snap command.
To activate the object list marker:
Every attempt has been made to ensure that the object list marker resizes and redraws correctly if the image display window is resized manually, or if the displayed image is zoomed, panned, etc.
The object list marker menu contains a selection of single object object list viewing, editing, and measuring functions, plus a small number of marker manipulation functions.
To use the object marker menu:
f | Select next object # Move to next object in object list b | Select previous object # Move to previous object list object ~ | Select current object # Select current object list object d | Delete current object # Delete current object list object u | Undelete current object # Undelete deleted object list object o | Measure next object # Measure next object in object list - | Measure previous object # Measure previous object in object list . | Measure current object # Measure current object in object list | Object region colors # Set object region marker colors | Sky region colors # Set sky region marker colors | Redraw marker # Redraw the marker | Dismiss the marker # Dismiss the markerNote that the keystroke accelerators associated with the menu items are the same as those that would be typed directly in the image display window, i.e. typing d in the object marker is the same as moving to the same object in the image display window and typing d if the marker were not there.
To delete the object marker:
More about using the object list marker to browse and measure objects in the object list can be found in the Browsing the Objects List and Measuring Objects Through the Object List Marker sections.
If the sky fitting mode is concentric the sky portion of the photometry marker will activate concentric with the object portion; otherwise only the object portion will activate. To quickly toggle between concentric and offset sky fitting mode:
To activate the photometry marker:
To activate the offset sky marker if the photometry marker was created in offset sky mode or if the sky fitting mode was changed from concentric to offset while the marker was active:
To realign the sky marker if the the sky fitting mode was changed from offset to concentric while the marker was active and offset:
The marker is active and ready to accept commands when its border highlights and the cursor changes as the mouse is moved in and out of the marker. If several markers are stacked together as is often the case for the photometry marker, then the one whose border is highlighted is the one ready to accept commands. If the desired marker is not currently the active marker and moving into does not make it so, then click the middle mouse button to lower the current marker to the bottom of the stack until the desired marker is active, or the click left mouse button to raise the current marker to the top of the stack until the desired marker is active.
To move the photometry marker from one place to another:
To rotate the photometry marker:
To resize the photometry marker:
Polygon markers are currently a special case. They must be drawn and stored by the user using the Phot menu "Draw polygons ..." item or the v keystroke command prior to activating the photometry marker. If a polygon marker is requested but none has been defined then a rectangular marker will be created instead. Polygon markers can be moved, rotated, and resized just like any other marker. However at present the user cannot add and subtract vertices from the polygon marker interactively, although the IRAF Xgterm widget does provide support for this operation.
Every attempt has been made to ensure that the photometry marker resizes and redraws correctly if the image display window is resized manually or the displayed image is zoomed, panned, etc.
To select and item from the photometry marker menu:
Measure Measure object at marker position
Object geometry Set the object region marker geometry
Sky geometry Set the sky region marker geometry
Object colors Set the object region marker colors
Sky colors Set the sky region marker colors
Redraw marker Redraw the marker
Save to object list Save marker x,y,geometry to objects list
Save to psets Save marker geometry to skypars and photpars
Help ... Display help
Dismiss marker Dismiss marker
The menu Measure item measures the object at the position of the
photometry marker using the geometry defined by the marker not the
geometry in the skypars and photpars parameter sets. Note that even if
the marker was created using that geometry, there will still be minor
differences because of precision problems in reading back the marker
geometry.
The object and sky marker geometries can be modified using the "Object geometry" and "Sky geometry" menu items. Markers can be transformed to and from the shapes "circle", "ellipse", "rectangle", and "polygon". However if a polygon was not defined by the user prior to requesting a polygonal marker a rectangular marker will be created.
By default the object and sky parts of the marker take on the colors specified by the photpars pcolormark parameter and the skypars and scolormark parameters. The default colors can be changed by selecting the "Object colors" and "Sky colors" submenus.
To delete the photometry marker:
More about how to use the photometry marker to create and edit the objects list and to make photometry measurements can be found in the Creating the Objects List with the Photometry Marker, Adding Objects to the Objects List, and Measuring Objects Through the Photometry Marker sections.
More on defining the default global and / or image directories, defining the image list, and selecting the current image can be found in the Setting the Image Directory, Setting the Image Template, Browsing the Image List Sections, Browsing the Image Headers, section.
More information on examining the image headers can be found in the Browsing the Image Headers and Setting the Impars Parameters sections.
The parameter editing panel consists of the following elements:
If one or more new parameter values have been entered into the pset editing panel, but not yet entered into memory with the Apply button, the Apply button label and the new parameter values will be white instead of black and in order to alert the user that the new parameter values are not the current values.
More on setting good values for the various pset parameters can be found in the Setting the Dispars Parameters, Setting the Impars Parameters, Setting the Findpars Parameters, Setting the Omarkpars Parameters, Setting the Cenpars Parameters, Setting the Skypars Parameters, and Setting the Photpars Parameters sections.
Detail descriptions of the parameter sets can be found in the The Dispars Parameters, The Impars Parameters, The Findpars Parameters, The Omarkpars Parameters, The Cenpars Parameters, The Skypars Parameters, The Photpars Parameters, The Cplotpars Parameters, and The Splotpars Parameters sections.
More information on using the model fitting panel to examine stellar objects and estimate the hwhm of the psf can be found in the section on Setting the Hwhm of the Psf.
More about creating object lists can be found in the Creating Objects Lists From Objects Files, Creating Objects Lists Automatically, Setting the Impars Parameters, Setting the Findpars Parameters, Creating an Objects List with the Image Cursor, and Creating an Objects List with the Photometry Marker sections.
More about viewing, browsing, and editing the objects list can be found in the Viewing the Objects List, Setting the Omarkpars Parameters, Browsing the Objects List, Deleting and Undeleting Objects from the Objects List, and Adding Objects to the Objects List sections.
More about measuring the objects in the object list can be found in the Measuring Objects in the Objects List and Measuring Objects Through the Object List Marker sections.
A variety of object and sky region displays are available including simple image display, image display with contour overlay, image display with object or sky aperture overlay, contour plots, or surface mesh plots. Different plots can be selected using the Objdisplay and Skydisplay buttons. The default object and sky displays are image display with object or sky aperture overlays.
A variety of object and sky analysis plots are available, including major axis and position angle profile plots of the object and sky region, histogram plots of the sky region, and curve-of-growth and moments analysis plots for multi-aperture measurements. Different plots can be selected using the Objplots and Skyplots menu buttons. The defaults are major axis and histogram plots for the object and sky analysis respectively.
Cursor mode can be switched from the default image display window to any one of the plots windows in the photometry plots panel hitting the appropriate Activate button. In cursor mode users have access to all the usual IRAF builtin cursor keystroke and colon commands.
The photometry plots panel consists of the following elements:
object region definition [; [sky region definition]] e.g. 256.23 258.31 circle 25.0 256.23 258.31 circle 25.0 ; 256.23 258.31 circle 25.0 ; circle 30.0 40.0
Object regions may by points, circles, ellipses, rectangles, polygons, or undefined. Each geometry has its own syntax as shown below.
point: x y
circle: x y circle radii
ellipse: x y ellipse radii [axratio [pa]]
rectangle: x y rectangle radii [axratio [pa]]
polygon: x y polygon [[radii] {
xver1 yver1
xver2 yver2
... ...
xverN yverN
}]
undefined: x y INDEF [INDEF [axratio [pa]]
e.g.
256.23 258.31
256.23 258.31 circle 25.0
256.23 258.31 ellipse 25.0 0.75 33.0
256.23 258.31 rectangle 25.0 0.75 33.0
256.23 258.31 polygon 5,10,15 {
100.0 100.0
200.0 100.0
200.0 200.0
100.0 200.0
}
356.23 358.31 polygon 5,10,15
256.23 258.31 INDEF INDEF
The x and y coordinates are required in all cases. The radii field may
define a single radius, e.g. "10.0", a list of radii, e.g. "3,6,9,12,15,18",
or a range of radii, e.g. "1:20.0:2.0". If a polygon radii field is
present it is treated as a width, and the polygonal aperture is extended
outward by that amount. Missing or INDEF valued required
radii fields will automatically have their geometries set to INDEF. All
radii measurements are assumed to be in the units of the
impars iscale parameter. Missing axis ratio
and position angle fields are assigned the values of 1.0 and 0.0 respectively.
If the vertices field of a polygonal object is ommitted the last defined
object polygon is used. If no object polygon has been defined by the time the
first polygonal object appears in the list, the object geometry is set to INDEF.
Sky regions may by points, circles, ellipses, rectangles, polygons, objects, or undefined. The object option means use the same geometry as the object region. Each geometry has its own syntax as shown below.
point: [x y INDEF]
circle: [x y] circle srin srout
ellipse: [x y] ellipse srin srout [axratio [pa]]
rectangle: [x y] rectangle srin srout [axratio [pa]]
polygon: [x y] polygon [[srin srout] {
xver1 yver1
xver2 yver2
... ...
xverN yverN
}]
object: [x y] object srin srout
undefined:
e.g.
256.23 258.31 ; 356.23 358.31
256.23 258.31 ; circle 30. 40.
256.23 258.31 ; 356.23 358.31 circle 30. 40.
256.23 258.31 ; ellipse 30. 40.
256.23 258.31 ; 356.23 358.31 ellipse 30. 40.
256.23 258.31 ; 356.23 358.31 ellipse 30. 40. 0.75 48.2
256.23 258.31 ; rectangle 30. 40.
256.23 258.31 ; 356.23 358.31 rectangle 30. 40.
256.23 258.31 ; 356.23 358.31 rectangle 30. 40. 0.75 48.2
256.23 258.31 ; 356.23 358.31 object
256.23 258.31 ; polygon 10 15 {
100.0 100.0
200.0 100.0
200.0 200.0
100.0 200.0
}
256.23 258.31 ; 356.23 358.31 polygon 10 15 {
100.0 100.0
200.0 100.0
200.0 200.0
100.0 200.0
}
Sky regions may be concentric with the object region, i.e. no x and y
sky region coordinates are defined, or offset, i.e. the x and y coordinates
are defined. If the sky geometry is "object", then the sky region inherits
the geometry, axis ratio, and position angle of the object region. The inner
and out sky annulus radii must be defined for all geometries except polygonal.
Missing or undefined axis ratio and position fields are assigned values
of 1.0 and 0.0 respectively.
dx = x - XCENTER
dy = y - YCENTER
dI = I - MSKY
Mxx = sum (dI * dx * dx) / sum (I - MSKY)
Mxy = sum (dI * dx * dy) / sum (I - MSKY)
Myy = sum (dI * dy * dy) / sum (I - MSKY)
HWIDTH = sqrt (log (2) * (Mxx + Myy))
ELL = sqrt ((Mxx - Myy) ** 2 + 4 * Mxy ** 2) / (Mxx + Myy)
AXRATIO = 1.0 - ELL
PA = 0.5 * atan (2 * Mxy / (Mxx - Myy))
SHARPNESS = HWIDTH / FWHMPSF
x, y, and I are the pixel coordinates and intensity value of each pixel contributing to the computation. XCENTER, YCENTER, and MSKY are the pixel centers and best sky value produced by the centering and sky fitting routines. Mxx, Mxy, and Myy are the second order central moments, and HWIDTH, ELL, PA, and SHARPRAT are the estimated half-width at half-maxima, ellipticity, position angle, and sharpness ratio respectively. The HWIDTH estimates are exact if the object is a perfect Gaussian. The ellipticity is defined as 1 - axratio. Position angles are measured counter-clockwise from the positive x axis. The sharpness ratio is the ratio of the measured HWIDTH to the value of the impars ihwhmpsf parameter supplied by the user.
MAG = 2.5 log10 (FLUX) FLUX = SUM - AREA * MSKY
MAG = -2.5 log10 (FLUX) ERROR(MAG) = 1.0857 * ERROR (FLUX) / FLUX ERROR(FLUX)^2 = FLUX / IGAIN + AREA * STDEV^2 + AREA^2 * STDEV^2 / NSKY
The object list widget has a builtin upper limit of around 2200 objects, beyond which the scrollbars will not function correctly. Xguiphot will still mark and measure longer lists, but functions like select, delete, and undelete on the List panel will not be available.
Marker support for polygonal apertures is available but is not fully general. Users can draw polygons on the image display, move them around, and measure through them. Polygonal markers can be activated, rotated, and resized but it is not yet possible to alter the number of vertices from those marked on the display, except by drawing a new polygon.
Xguiphot currently contains 6 XGterm widgets, 3 for vector graphics, and 3 for image display. The 3 vector graphics widgets behave exactly like a normal IRAF XGterm widget, once their associated Activate button is pushed. So do the image display widgets with the exception that snaps and hardcopies of the displayed image do not work and will currently produce blank plots. Any overlay graphics however will be snapped.
The main image display window is also an xgterm widget, and it has the same problem with printing as the object and sky region widgets. Cursor mode is otherwise fully functional in this window, with the following limitation. If a cursor mode zoom or pan function, e.g. Z, M, P, E, 0 etc is executed in the image display window when the last graphics object displayed was not the image, then the user will get an unpleasant surprise when one of these keystrokes is executed. They will see the last plot appear in the image display window rather than the redisplayed image. A simple i keystroke will fix the problem but any overlayed graphics will be lost. This problem is due to their being only one true graphics buffer in IRAF. The problem is solved for other plots by redisplaying their contents when the plots are activated. However it is inefficient and annoying to do this for images.