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emsao



.help emsao Jan2005 rvsao
.ih
NAME
emsao -- Compute redshift by identifying shifted emission lines
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USAGE
emsao spectra
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PARAMETERS
.ls spectra = ""
List of file names of spectra to analyze.
@<filename> indicates list should come from file <filename>.
<filename>[<range>] indicates that a range of apertures in a multispec
file should be processed, where <range> is a comma- and/or hyphen-separated
list of numbers.
The files should be dispersion-corrected and linear in wavelength.
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.ls specnum = 0
If this is nonzero and \fIspectra\fR contains a single file name, this
is a range of spectrum numbers in a multispec file for which emission
line velocities will be obtained.  Wavelength dispersion information
is then read from APNUMn, and velocity information is read from APVELn,
APVXCn, and APVEMn and saved in APVELn and APVEMn, the values of which
contain multiple values.  If specnum is zero, velocity information is
in separate keywords for each value.
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.ls specband = ""
Spectrum band if multispec file
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.ls skynum = 0
If this is nonzero, the sky spectrum, which is used for equivalent width
errors, is read from this spectrum number of the current spectrum file
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.ls skyband = 0
Sky band if multispec file
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.ls specdir = "./"
Directory containing spectra to analyze
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.ls linefit = yes
If yes, search for emission lines fit their positions, and average
them into a weighted mean velocity for the spectrum.  If no, display
spectrum with labelled emission lines found in a previous application
of EMSAO and results from any previous XCSAO run which is archived in
the image header.
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.ls fixbad = no
If yes, replace portions of spectrum given in file \fIbadlines\fR with
a straight line linking the adjacent points.  This feature can be used
to eliminate emission and absorption features caused by poor removal of
night sky emission lines. (added in version 2.0)
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.ls badlines = "badlines.dat"
File containing list of starting and stopping wavelengths in Angstroms for
removal of portions of all object spectra.  All information after the
second wavelength is a comment field. This file is assumed to be in the
directory \fIlinedir\fR unless a complete pathname starting with "/" or
including a "$" is specified (added in version 2.0).
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.ls renormalize = no
If yes, renormalize spectrum before fitting by multiplying each pixel
by 1000 times the mean pixel value for the spectrum.  .  Set this to "yes"
for fluxed spectra.  If set to "no" and all values of the object spectrum are
less than 1, the spectrum is renormalized anyway, to avoid crashing the
program.
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.ls st_lambda INDEF
Starting wavelength in angstroms of portion of spectrum to use
If INDEF, start at beginning of spectrum.
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.ls end_lambda INDEF
Ending wavelength in angstroms of portion of spectrum to use
If INDEF, end at end of spectrum.
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.ls nsmooth 10
Number of times the spectrum is smoothed using a 1-2-1
sliding box before the emission line search occurs.  This smoothed
spectrum is also the version which is displayed.
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.ls vel_init "search"
The type of velocity to be used for the initial guess at where the emission
lines should be.
If "search", look for the lines in the \fIemsearch\fR file.
If "guess", use \fIczguess\fR.
If "correlation", use the \fICZXC\fR parameter in the file header which
was set by XCSAO.
If ("cortemp", use the velocity obtained by XCSAO when cross-correlating this
spectrum against the template specified by \fIcortemp\fR.
If "emission", use the \fICZEM\fR file header parameter which was set by
a previous run of EMSAO.
If "file", use the \fIVELOCITY\fR parameter from the header, a combined
velocity which is set by both EMSAO and XCSAO.
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.ls czguess 0.
Initial guess at the radial velocity if >1 or z if <1.  It is used only if
vel_init is "guess".
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.ls cortemp ""
Name of template from which to use cross-correlation velocity. (new in 2.0)
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.ls wspan 10.
Wavelength in angstroms to search around redshifted line center.  This
should always be less than the distance between the closest lines for
which you are searching.
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.ls linesig 2.0
A line peak must be this many standard deviations above the continuum to
qualify as a line.
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.ls emsearch "emsearch.dat"
File containing list of emission lines used to determine an initial
velocity guess if \fIvel_init\fR is "search".  Each line contains:
.br
	Center wavelength of line in angstroms
.br
	Starting wavelength in angstroms for search for this line
.br
	Ending wavelength in angstroms for search for this line
.br
	Name of line (terminated by end of line or space)
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.ls emlines "rvsao$lib/emlines.dat"
File containing list of emission lines, where the each line contains:
.br
	Center wavelength of line in angstroms
.br
	Starting wavelength in angstroms for continuum for this line
.br
	Ending wavelength in angstroms for continuum for this line
.br
	Half-width in angstroms for region to fit for this line
.br
	Name of line (terminated by end of line or space)
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.ls linedir = rvsao$lib/
Directory for emission and absorption information files.  If the name of
one of the individual files containis "/" or "$", it is assumed to be a
full path name, and \fIlinedir\fR is not used.
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.ls npfit 2
Number of pixels to fit around line peak (+-)
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.ls nlcont 1
Number of coefficients in line continuum fit (0-3).  An overall continuum
fit is subtracted, but the fit may not be good enough to remove the local
continuum.  If 0, no additional continuum is fit for each line.  If the
continuum is poorly subtracted using the parameters in \fIcontpars\fR,
values of more than 0 for \fInlcont\fR can cause trouble.
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.ls esmooth 0
Number of times the spectrum is smoothed using a 1-2-1 sliding box
before the emission lines are fit.  Normally 0, it can be set to 1 or 2
for very noisy data when the fitting subroutine may otherwise be
unable to fit a continuum.  It should be set no higher to avoid distorting
the emission line profiles.
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.ls emcombine "emcomb.dat"
File containing list of groups of emission lines which should be fit together.
Each entry contains the following information for one group of two to five lines:
.br
	Number of combined emission lines
.br
	Number of angstroms to add to fit beyond left and right line centers
.br
	For each emission line:
.br
		Center wavelength in angstroms
.br
		Relative line height
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.ls mincont 0.0
If continuum is greater than this value, compute the equivalent width
of the current line, which is the width the line would be if it were as high
as the continuum is deep.  If the continuum is less than or equal to this
value, compute the area of the line in counts times wavelength.  When
working with continuum subtracted spectra or spectra where the emission lines
are so strong that there is minimal continuum, make this value larger than
the largest possible continuum fit value to get consistently computed numbers.
(added in 2.0)
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.ls lwmin 0.4
Minimum fraction of mean line width for individual line (added in 2.0)
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.ls lwmax 1.7
Maximum fraction of mean line width for individual line (added in 2.0)
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.ls lsmin 2.0
Minimum equivalent width in sigma for individual line (added in 2.0)
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.ls sigline 0.0
Velocity error if single line found.  Use gaussian fit error if 0 or
INDEF.  This value may need to be set higher to use a good, but different
cross-correlation properly when the program computes a combined velocity.
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.ls disperr = 0.01
RMS dispersion error in Angstroms
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.ls vel_corr "file"
Spectrum velocity correction to the solar system barycenter.  Set to
"none" if spectrum has already been shifted or if this correction is
unnecessary.  If "file", \fIBCV\fR is used if present in the file header,
or else \fIHCV\fR.  If "hfile", the header parameter \fIHCR\fR is always
used.  If neither is found, no correction is made.  If "heliocentric"
or "barycentric" corrections are chosen, position and time parameters
are read from the spectrum data file header.  \fIDATE-OBS\fR (date in
format 'dd-mm-yy') \fIUT\fR (U.T. at end of exposure as 'hh:mm:ss')
and \fIUTOPEN\fR (U.T. at start of exposure as 'hh:mm:ss') or
\fIEXPOSURE\fR (length of exposure in seconds) are used to compute
the midtime of the exposure.  \fIRA\fR (right ascension as 'hh:mm:ss.ss'),
\fIDEC\fR (declination as 'dd:mm:ss.ss'), and \fIEPOCH\fR (epoch of
coordinates defaults to 1950.0) give the position of the object whose
spectrum this is.  \fISITELONG\fR (observatory longitude as 'dd:mm:ss.ss'
or degrees), \fISITELAT\fR (observatory latitude as 'dd:mm:ss.ss' or
degrees), and \fISITEELEV\fR (observatory altitude in meters) give the
observatory position.
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.ls report_mode = 1
Format of report sent to \fIlogfiles\fR.  A tab table with column headings
is written if the mode flag is negated.
.ls =1  Full information on each emission line found
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.ls =2  One line per spectrum, with combined, cross-correlation, and
emission line velocities, number of lines found and fit, and a list of
names and wavelengths of the lines which were used in the fit.
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.ls =3  One line per spectrum, with combined, cross-correlation, and
emission line velocities, number of lines found and fit, and velocities
for all possible reference lines, with velocities of lines not used in
the final fit set to 0.
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.ls =4  One line per spectrum, with file name, instrument, object, right
ascension, declination, altitude, azimuth, Julian date, exposure, emission
velocity and error, cross-correlation velocity, error, and R-value (for
the template specified by cortemp or best template value if cortemp is ""),
and the combined velocity and error. Following the number of lines found
and the number of lines fit, the velocity, error, height, width, and
equivalent width are then given for each line, with zero values indicating
that the line was not used in the fit. If the continuum under the line is
less than mincont, the area of the line is given instead of the equivalent
width.
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.ls =5 Same as mode 2, but emission line template cross-correlation velocity
is always given as the cross-correlation velocity.
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.ls =6 Same as mode 3, but emission line template cross-correlation velocity
is always given as the cross-correlation velocity.
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.ls =8 Single line report with line offset, error, height, width, and
equivalent width for each emission line
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.ls =9 Single line report with line offset for each emission line
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.ls archive = no
If yes, save emission line results in SAO TDC archive record.
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.ls save_vel = no
If yes, save results in the IRAF image header.  Combined velocity and
error are stored as \fIVELOCITY\fR and \fIVELERROR\fR.  Emission line
velocity and error in IRAF image header as \fICZEM\fR and \fICZEMERR\fR,
and the number of lines used in the fit is in \fICZEMNLF\fR
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.ls verbose = yes
If yes, results of the emission line search are logged.
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.ls logfiles = "STDOUT,emsao.log"
All results from \fIemvel\fR are recorded in these files.
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.ls device = "stdgraph"
Device on which to display graphic summary of results.
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.ls hardcopy = no
Print graphic summary of results on \fIplotter\fR.
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.ls displot = yes
If yes, graph data on terminal (yes or no)
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.ls plotter = "stdplot"
If \fIhardcopy\fR is yes, make hardcopies of graphs on this device.
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.ls dispmode = 2
Graphical display mode (2=with line list 3=full screen)
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.ls vel_plot "emission"
The redshift of this velocity is used to compute the positions of the
absorption and emission lines which are flagged in the display.  Choices
are emission, correlation, or combination (a weighted combined velocity).
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.ls curmode = yes
If yes, stop in cursor mode after plotting and labelling spectrum and
wait for cursor commands described below.
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.ls dispem = yes
If yes, flag positions of emission lines which have been found.  Those
used in the velocity fit are plotted as solid lines.  The "-" cursor
command can be used to delete these from the fit.  Those lines found but
omitted from the fit are plotted as dashed lines.  The "+" cursor
command can be used to add them to the fit.
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.ls dispabs = yes
If yes, flag positions of absorption lines.
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.ls ablines "ablines.dat"
File containing list of absorption lines to plot, where the each line contains:
.br
	Center wavelength of line in angstroms
.br
	Name of line (terminated by end of line or space)
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.ls velfit = yes
If yes, combine the redshifts found for individual emission lines into a
single emission line velocity. (eliminated from 1.8 on)
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.ls obj_plot yes
If yes, a plot of the object spectrum is displayed before the emission
lines are searched for.
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.ls contsub_plot = no
Plot the continuum-subtracted data
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.ls debug = no
If yes, intermediate values of the parameters are recorded in the log files.
Too much information is printed to be useful for anything but debugging.
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.ls nsum = 1
Number of pixels to sum across dispersion
.ls cursor = ""
Graphics cursor input.  When null the standard cursor is used otherwise
the specified file is used.
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.ih
DESCRIPTION

\fIemsao\fR finds emission lines, computes redshifts for each identified line,
and combines them into a single radial velocity.  The results may be
graphically displayed or printed.  If \fIcurmode\fR is set, the graphic
cursor remains active after the spectrum is plotted and labelled, and
the following keystrokes may be used to redisplay and/or rework the
fit (in addition to the standard IRAF cursor facilities, a menu of which
can be obtained by typing :.help):
 
.ls ?
Print list of \fIemsao\fR cursor commands.
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.ls a
Set redshift guess from an absorption line at the cursor position.  Respond to
the prompt with either the line name from the ablines.dat file or a specific
wavelength, which doesn't have to be one of the tabulated lines, in Angstroms.
It might help to set the smoothing to 0 using \fIn\fR before doing this.
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.ls b
Set blue limit of spectrum to be searched to current cursor position. 
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.ls c
Force the final velocity to a specific value which may be 
.ls e the emission line velocity, 
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.ls x the cross-correlation velocity as read from the spectrum header, 
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.ls c the combination velocity as computed by emsao, 
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.ls g the initial guess as set by emsao.vel_init, 
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.ls s a specific velocity and error to be typed in. 
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.ls d
Replaces a region between the marked vertical cursors with interpolated
values from the edges of the marked region.  This is typically used to
eliminate poorly subtracted night sky lines or emission lines.
\fIx\fR can be used to cancel the first \fId\fR.
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.ls e
Set redshift guess from an emission line at the cursor position.  Respond to
the prompt with either the line name from the ablines.dat file or a specific
wavelength, which doesn't have to be one of the tabulated lines, in Angstroms.
It might help to set the smoothing to 0 using \fIn\fR before doing this.
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.ls f
Refit the redshift. If lines have been added or deleted, a new weighted
mean is computed. If a new initial guess has been set or line fitting
parameters have been modified, a new line search is done. 
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.ls g
Change number of times spectrum is smoothed (nsmooth) to the number given
in response to prompt. It may help to set this to 0 before identifying
emission or absorption lines using e or a. 
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.ls i
Reset the initial velocity for the line search. 
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.ls k
Toggle between display with continuum subtracted and display with continuum
included (default).  This works for both dispmode=1 and dispmode=2.
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.ls l
Reset the \fIlinesig\fR and \fIwspan\fR parameters which determine the
the number of standard deviations above the continuum at which to define
an emission line and the wavelength to search around the redshifted center
of an individual line. 
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.ls m
Change number of times spectrum is smoothed (\fIesmooth\fR) for line fitting
to the number given in response to the prompt.  This should be zero unless
high noise levels are preventing good line fits in which case it may be set
to 1, or at most, 2.
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.ls n
Disaprove the final velocity and set the quality flag to X.
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.ls p
Replot the current display.
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.ls q
Quit and exit.
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.ls r
Set the red limit of spectrum to be searched to current cursor position.
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.ls s
Set the redshift guess from an entered rest wavelength for the current
cursor position.
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.ls t
Use the velocity from the nth template in the list displayed in a
emsao.dispmode=1 summary display. 
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.ls u
Forces the current spectrum to be replotted at the original scale.
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.ls v
Select the source of the redshift at which the absorption and emission
lines are plotted.  It may be an emission, correlation, or combined
radial velocity from the image header as \fICZEM\fR, \fICZXC\fR, or
\fIVELOCITY\fR.
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.ls w
Show rest and observed wavelength at cursor position.
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.ls x
Cancel \fId\fR and \fIz\fR commands before second keystroke.
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.ls z
Replots the region of the spectrum in wavelength between successive
uses.  \fIx\fR can be used to cancel the first \fIz\fR.
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.ls +
Add closest found emission line to the velocity fit if it has been
dropped, overriding program's selection criteria.  If this doesn't work,
use the \fIv\fR command to plot using the emission velocity.
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.ls '-'
Drop closest found emission line from the velocity fit if it has been
used, overriding program's selection criteria.  If this doesn't work,
use the \fIv\fR command to plot using the emission velocity.
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.ls '.'
Cancel delete (d) or zoom (z) command. 
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.ls '/'
Toggle between spectrum plus summary display (dispmode=1) and full screen
spectrum display (dispmode=2).
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.ls @
Make hard copy of graph to \fIplotter\fR.
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.ih
EXAMPLES
To obtain the redshift and dispersion of a single galaxy

        cl> emsao galaxy

To obtain redshifts for a whole night's worth of galaxy spectra:

        cl> emsao @nite1.ls

where the file nite1.ls contains the name of the galaxy images.
.ih
SEE ALSO
On-line help is available on the World Wide Web at
http://tdc-www.harvard.edu/iraf/rvsao/emsao
.endhelp

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