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. 
