22 Dec 99 Modified magnitude definitions. 13 Jan 98 Added upper and lower sigma-clip thresholds. 20 Oct 97 Added variable threshold in object locator. 22 Sept 97 Changed the starting gradient value, from 1/10 of the current mean value, to -0.05. The former value wasn't working for some images. 16 Sept 96 Created new task 'isoexam'. 13 Sept 96 ellipse was modified in order to read ellipse geometry information from a previously generated table and perform photometry only (no fit). 23 Jul 96 Added wander limits for ellipse center. Also fixed PAe labels in table and plot, and added image and graphics cursor parameters. 12 Jun 96 Second version rolled into standard "isophote" STSDAS place. Nov 1995 Beta release of second version. 04 Sep 1991 Fixed bug in ellipse.par. Changed a0 and maxa parameters from INDEF- value hidden parameters to mandatory parameters with reasonable default values. 04 Sep 1991 Fixed bug in isoplot.par and isopall.par. The CL handles parameter range checking in strings. In this particular case, the xaxis parameter in both tasks has as allowed values "a" and "a**1/4". However, since both strings begin with the character "a", the CL is unable to handle the selection properly. In these new versions, there is no more range checking string in xaxis definition. 06 May 1991 Fixed bug in elfit.x. The algorithm was unable to work on images with small pixel intensities (~<1.e-7). The problem was traced to the code that handles the case of very small radial intensity gradients. Code was changed to work with relative (percentual) gradients instead. 02 May 1991: Changed output formats in elcolnames.h, from 'f' to 'g' real. 02 May 1991: Fixed bug in elfit.x. The algorithm was not handling properly the case of negative ellipticity. This generated sometimes curious behavior in the first fitted isophote, like a wrong, underestimated intensity level. The bug manifested itself in a way which was data-dependent. 08 Jan 1991: Two bugs were fixed in 'ellipse' task: (i) wrong position angle error was being displayed by 'show' colon command; (ii) the intensity samples (intensity versus angle files) were being output with the 1st and 2nd harmonics subtracted. 10 Dec 1990: Fixed an error which prevented the 'n' cursor key to work properly, when the initial ellipse was being input by cursor commands. 21 Sep 1990: Task 'ellipse' was modified to handle a bad pixel list. The list can be created outside the task and input to it, or it can be created/updated, when in interactive mode, by the cursor keys 'e' and 's'. 20 Sep 1990: The image reconstruction algorithm used in task 'model' was modified as to work with fractional pixel offsets. This produces much more accurate modelling of the central galaxy regions (a < 10 pixels), where the radial intensity gradient is usually large. Files bmodel.par and bmodel.hlp were also modified. 10 Sep 1990: A new version of the package was installed. Besides minor bug fixes in the plotting tasks, a major upgrade on the ellipse fitting task `ellipse' was carried out: now there is an interactive mode. Both stdgraph and imdX devices are supported. Other modifications include: (i) automatic clipping off of deviant data points; (ii) sub-pixel integration at the central region; (iii) ellipse geometric parameters can be hold fixed; (iv) linear growing radius; (v) extra harmonics can be fitted and output. 02 Aug 1990: Changed sign of 3rd and 4th harmonic amplitudes, to be compatible with the convention used in the literature to describe 'boxy' and 'disky' isophotes. 30 Jul 1990: Task 'isomap' produced wrong superposition of image contours and ellipses when using image sections in task 'ellipse' input. It works correctly now, but numerical truncation still produces small errors, when the section has a sampling > 1. 30 Jul 1990: Changed definition of ellipse position angle. Now it is measured counterclockwise from the +y direction. Files affected: ellipse.x, eldump.x. 27 July 1990: The file name (plus section) of the original image analysed by task 'ellipse' is now added to the output table as a header parameter. Files affected: ellipse.x, elopens.x. 18 July 90: Modified error calculation for ellipse geometrical parameters and Fourier harmonic amplitudes. The new error definition depends on the residual rms after removal of the harmonics up to, and including, the one being considered. Fixed inconsistent plotting of error bars, due to the way sgraph interprets errors in a sdas table. Files affected: tasks/elfit.x, tasks/elharmonics.x, isoplot.cl, isopall.cl 04 Jun 1990: An incompatibility in column names used by two tasks generated a segmentation violation error in task 'bmodel'. Column names were moved to an include file (elcolnames.h). The affected source files were modified accordingly. Modified files are: elapert.x, ellipse.x, elopens.x, map.x, model.x 09 March 1990: When extrapolating a table, trebin can generate negative values for the ellipse semi-major axis. This introduced an infinite loop in the hidden task map. Corrected the problem. 01 March 1990: Problems were corrected in the magnitude calculation (and plotting) of negative numbers. Files modified: eldump.x, ellipse.x, isoplot.cl, isopall.cl. Also, corrected problems with a table column named 'int' by renaming it 'meanint'. Modified files: elopens.x, isomap.cl, isoplot.cl, ellipse.hlp. 12 February 1990: Moved the isophote analysis tasks from 'stlocal.stsurfphot' to a new top-level package named 'isophote'. Removed stsurfphot from stlocal. 07 February 1990: The isophotal magnitude calculation was undefined when the isophotal intensity was negative. Changed log function to elogr (in gio), to take care of negative intensities. 26 December 1989: Added a new task (ELAPERT) to build elliptical apertures for use in the APPHOT.POLYPHOT polygonal aperture photometry task. 20 December 1989: Improvements were made in tasks ELLIPSE and MODEL (hidden task called by BMODEL) to increase the execution speed. 07 December 1989: Fixed a bug in the hidden task MODEL. The background value of model image wasn't being generated correctly. 19 November 1989: New tasks were added to the package: BMODEL, which builds a model image based on the results of isophotal analysis generated by task ELLIPSE; and ISOMAP, which graphs image contours with ellipses superimposed on them. Upgraded the task ELLIPSE, which is now able to integrate the intensity information along elliptical annulus sectors over the image. ELLIPSE can now generate an optional set of files with the intensity versus eccentric angle information for each fitted isophote. Some minor corrections were also made in several pieces of code in this package, mainly to get rid of incompatibilities between the script tasks which depend on SGRAPH. 25 October 1989: Installed a new subpackage in stlocal, which contains the elliptical isophote fitting task "ellipse", as well as auxiliary tasks intended to examine the results of isophotal analysis. This software was not installed in the playpen package, as initially intended, because playpen is not available on some Institute machines.