IRAF help page for package noao.digiphot.apphot, program fitpsf

Image and coords are the name of the image and coordinate files respectively. Id and lid are the sequence numbers of stars in the output and coordinate files respectively and xinit and yinit are the initial positions. Xcenter and ycenter are the computed x and y positions of the object. Rsigma, xsigma and ysigma are the distance from the center of the Gaussian at which the Gaussian is equal to exp (-0.5) of its central value. Xsigma and ysigma refer to those values along the x and y axes respectively. The amplitude and sky refer to the amplitude of the Gaussian function and a constant background value respectively. If function = "moments" amplitude and sky refer to the total intensity above threshold and sky is the threshold value. Rot and pa are position angles of the major axis measured counter-clockwise with respect to the x axis. Rgyrat is the radius of gyration of the object and ellip its ellipticity. Quantities prefixed by an e represent the errors in the corresponding fitted parameters.

If all went well in the fitting process the error code stored in the ier field described above is 0. Non-zero values of ier flag the following error conditions.

          0     # No error
	401     # The fitting box is off the image
	402     # The fitting box is partially off the image
	403     # There are too few points to fit the function
	404     # The fit is singular
	405     # The fit did not converge

1. Compute the radial Gaussian function parameters for a few stars in N4147 using the display and the image cursor. Setup the task parameters using the interactive setup menu defined by the i key command.

	ap> set stdimcur = stdimage
	... define the image cursor
	ap> display n4147 1 fi+
	... display the image
	ap> fitpsf n4147
	... type ? to get a short help page on the screen
	... move the image cursor to a star
	... type i to enter the interactive setup menu
	... enter maximum radius in pixels of the radial profile
	... set the fitting box width, fwhmpsf, and sigma using the graphics
	    cursor and the stellar radial profile plot
	... typing  leaves everything at the default value
	... type the v key to verify the parameters
	... type the w key to save the parameters in the parameter files
	... move the image cursor to the stars of interest and tap
	    the space bar
	... a one line summary of the fitted parameters will appear on the
	    standard output for each star measured
	... the full output will appear in n4147.psf.1

2. Compute the radial Gaussian function parameters for a few stars in M92 using the contour plot and the graphics cursor. Setup the task parameters using the interactive setup menu defined by the i key command.

	ap> set stdimcur = stdgraph
	... define the image cursor to be the graphics cursor
	ap> contour m92 >G m92.plot1
	... store the contour plot of m92 in the file m92.plot
	ap> fitpsf m92 display=stdgraph
	... type ? to get a short help page on the screen
	... type :.read m92.plot1 to load the contour plot on the screen
	... move the graphics cursor to a star
	... type i to enter the interactive setup menu
	... enter the maximum radius in pixels of the radial profile
	... set the fitting box width, fwhmpsf, and sigma using the graphics
	    cursor and the stellar radial profile plot
	... typing  leaves everything at the default value
	... type the v key to verify critical parameters
	... type the w key to save the parameters in the parameter files
	... retype :.read m92.plot1 to reload the contour plot
	... move the graphics cursor to the stars of interest and tap
	    the space bar
	... a one line summary of the fitted parameters will appear on the
	    standard output for each star measured
	... full output will appear in the text file m92.psf.1 

3. Setup and run FITPSF interactively on a list of objects, using a contour plot as the image display and the parameters defined and saved in example 2.

	ap> set stdimcur = stdgraph
	... define the image cursor to be the graphics cursor
	ap> contour m92
	... adjust plot parameters until the contour plot is satisfactory
	ap> =gcur
	... enter cursor mode
	... type :.write m92.plot2 to save the plot in a metacode file
	... type any key to quit cursor mode
	ap> daofind m92
	... make a coordinate list by searching for objects with  the
	    fwhmpsf and threshold defined in example 2
	... the output will appear in the text file m92.coo.1
	ap> fitpsf m92 coords=m92.coo.1 display=stdgraph
	... type ? for optional help
	... type :.read m92.plot2 to read in the contour plot
	... move the graphics cursor to the stars and tap space bar
				or
	... use m, :m and/or n, :n, l, r commands to measure objects in the
	    coordinate list
	... a one line summary of results will appear on the standard output
	    for each star measured
	... the output will appear in m92.psf.2 ...

4. Run FITPSF in batch mode using the coordinate file and the previously saved parameters. Verify the critical parameters.

	ap> fitpsf m92 coords=m92.coo.1 verify+ inter-
	... output will appear in m92.psf.3 ...

5. Run FITPSF in batch mode using the coordinate file and the previously saved parameters. The task can be submitted to the background by appending an ampersand to the command line listed below.

	ap> fitpsf m92 coords=m92.coo.1 verify- inter-
	... output will appear in m92.psf.4

6. Run FITPSF interactively on the Sun workstation without the use of the IMTOOL window using only a coordinate list and the current set of parameters as input.

	ap> set stdimcur = text
	... set the image cursor to the standard input
	ap> fitpsf m92 coords=m92.coo.1
	... type ? for optional help
	... type :m 3 to set the initial coordinates to those of the
	    third star in the list
	... type i to enter the interactive setup menu followed by v to
	    get the default menu
	... enter maximum radius in pixels of the radial profile
	... set the fwhmpsf, sigma, and fitting box half-width
	    using the graphics cursor and the stellar radial profile plot,
	    typing  after the prompt leaves the parameter at its default
	    value
	... type r to rewind the coordinate list
	... type l to measure all the stars in the coordinate list
	... a one line summary of the answers will appear on the standard
	    output for each star measured
	... full output will appear in the text file m92.psf.5 

BUGS

In interactive mode the user should not change the type function to be fit after the first record is written to the output file. In this case the file header and record structure will not match.

It is currently the responsibility of the user to make sure that the image displayed in the frame is the same as that specified by the image parameter.

Commands which draw to the image display are currently disabled. The TVMARK task in the proto package can be used to draw simple marks on the display. All the APPHOT marking commands will however function if a contour plot is used in lieu of the image display.

Users should not be confused by the normally enabled markcur option in the SUN/IMTOOL setup window. This feature is under the control of the IMTOOL window and the APPHOT package has no control over it.

datapars, radprof,