### 4 PARAMETERS

This is a complete list of all the parameters used by echomop tasks.

ARC = _CHAR

The names of all reference images to be used for wavelength calibration must be supplied here. The number of images should be equivalent to the number specified for parameter NREF_FRAME. The image names should be separated by commas, for example: reffrm1, reffrm2.

Note that in most circumstances there will only be two reference frames. One taken prior to the object frame, and one subsequently. If you do not wish to provide an arc frame at all then you may reply NONE is response to this prompt or, alternatively set the parameter TUNE_NOARC=YES. If no arc is available then you must provide your own sets of wavelength feature positions, or wavelength scales, if wavelength calibration is required.

ARC_TYPE = _CHAR

As of echomop v3.3-0, this parameter is ignored and should be removed from any scripts using it. The reference-line database should be specified by the parameter ECH_FTRDB. The parameter will be completely removed at the next release of echomop.
ASCII_FILE = _CHAR

The name of the ASCII data file to be produced.

The default is echomop_output.txt.

AUTO = _LOGICAL

If AUTO=YES then echomop will use all the options available to automate the processes it invokes. Currently the following parameters will be affected:
• TRC_INTERACT set to NO.
• TRC_VETO set to NO.
• ID_INTERACTIVE set to NO.
• CR_INTER set to NO.
• 2D_INTERACT set to NO.
• PFL_INTERACT set to NO.
AUTO_ID = _LOGICAL

Specifies that automation is required when arc line identification is being done. Interactively, options are available to allow you to tune the fitted wavelength polynomial, add/delete features etc. If AUTO_ID is set to YES then the package will try to identify the arc line features automatically. For orders with sufficient features this will usually be successful ( $>$12 lines), and a useful strategy is probably to do an automatic run first, and then manually examine the fitted features to verify their suitability.

Specifies an order which is to be disabled from further processing.

The default value is zero which is ignored, in case of a mistake.

Orders are disabled by writing the ‘bad value’ quantity into the first coefficient of the trace polynomial. This ensures that they also appear disabled to other tasks (almost all of which will need the trace polynomials).

To re-enable an order, re-fit a polynomial to its traced path, using ech_fitord/echmenu option 3.

BIN_SIZE = _REAL

Specifies the bin size in wavelength units. This bin size is only used when scrunching to a global wavelength scale. By default the program will calculate an appropriate bin size for you, but this parameter allows you to override this by supplying a non-zero value.

Initial suggested value: 0.0.

BLZFIT = _CHAR

This parameter selects the type of line fit for blaze function fitting.

The recognised functions are POLY (the default), MEDIAN and SPLINE.

Note that the required maximum number of coefficients is different in each case. For POLY the maximum number of coefficients corresponds to the number of degrees plus one, so for a cubic use coeffs=4. For a SPLINE the maximum number of coefficients corresponds to 2x(knots+7), so for 3 knots use coeffs=20. If you are using SPLINE fits then you should ensure that the value of TUNE_MAXPOLY is set accordingly, as well as using an appropriate value for BLZ_NPOLY.

When MEDIAN is selected local medians of X-extent BLZ_NPOLY-pixels are used as the blaze function.

Initial suggested value: POLY.

BLZ_INTERACT = _LOGICAL

Set to YES if the blaze fitting is to be done interactively. Automatic fitting is performed otherwise.

Initial suggested value: NO.

BLZ_NPOLY = _INTEGER

The default number of coefficients to be used when fitting functions to the order blaze.

The type of function to be used is set using the parameter BLZFIT (default is POLY for polynomial).

When BLZFIT=POLY then the number of coefficients should be set to degree of polynomial + 1.

When BLZFIT=SPLINE the number of coefficients should be set to 2 x (number of knots + 7).

When BLZFIT=MEDIAN the number of coefficients should be set to the number of pixels over which a local median value of the blaze function is to be found.

For example, setting BLZ_NPOLY to 4 would permit the fitting of polynomials of the form:

constant + ax + bx squared + cx cubed

Initial suggested value: 7.

CENTRAL_ONUM = _INTEGER

Parameter is ‘hidden’
CENTRAL_WAVE = _REAL

Parameter is ‘hidden’
CR_OUTPUT = _CHAR

The name of the output image containing a copy of the original with suspected cosmic-ray pixels replaced either by interpolation, or by flag values.
DECIMG = _CHAR

The name of the raw image in which cosmic-ray-pixel detection is to be performed.

Pixels may be either replaced with an interpolated value, or by a flag value.

DISPLAY = _LOGICAL

If DISPLAY=YES is used, then an imaging device is assumed to be available and some programs in the package will overlay plots on the image to help illustrate their results.

For example, the paths of the orders as fitted with polynomials will be overlaid on a part of the traced image.

Initial suggested value: NO.

ECH_ECHAR = _CHAR

The name of the file to use to exchange data with the ECHARC program.
ECH_FTRDB = _CHAR

The name of the file containing the reference line list database.

The database is built from a .ARC file using the task ech_ftrdb.

The database should have the same file name as the .ARC file used for its creation. The default is to use $ARCDIRS/THAR. Note the use of the$ARCDIRS environment variable to specify the search path for arc databases. This should normally be used as it searches in the normal fiGARO order. If you wish to specify a private database then the full pathname may be provided, e.g., /mydisk/mydir/sub/ANARC.

If no arc database exists for the .ARC list you want to use then use the ech_ftrdb task to create a copy. You might like to check to see if anyone local already has the database you need.

Initial suggested value: ’\$ARCDIRS/THAR’.

ECH_RDCTN = _CHAR

The name of the file created to hold the data reduction history.

This file will normally be created by the first echomop task run. Any valid datafile name can be used.

By default the file is created in the current directory.

ECH_RDUCD = _CHAR

The name of the file to save data to.
ECH_STRUCT = _CHAR

The name of the file containing the definition used to create a reduction database.
EXTRACT_MODE = _CHAR

The type of extraction to perform.

This may be one of the following:

O — Optimal (default).

S — Simple.

P — Profile weighted.

FFIELD = _CHAR

The name of the flat-field frame.

The package uses this frame to calculate balance factors on a per-pixel basis. If a balance frame is already available, then the frame should be supplied instead of a flat field, and the parameter TUNE_PREBAL should be set.

If you do not wish to supply a flat field at all, then you may either reply NONE to this prompt (must be uppercase), or set the parameter TUNE_NOFLAT=YES.

If no flat-field frame is supplied then the balance factors will be set to unity for all pixels.

FLAG = _REAL

If interpolation is not required, the suspected cosmic-ray pixels will be replaced using the supplied flag value.
FLTFIT = _CHAR

The type of fit to be used for flat-field modelling.

The available functions are MEAN (the default), POLY, SPLINE, MEDIAN, SLOPE and SMOOTH.

All modes except POLY and SPLINE use local neighbourhoods delineated using a sample size (in pixels) defined by TUNE_FFLSMP.

Note that the required maximum number of coefficients for POLY and SPLINE are different. For POLY, the maximum number of coefficients corresponds to the number of degrees plus one, so for a cubic use coeffs=4. For a SPLINE the maximum number of coefficients corresponds to 2x(knots+7), so for 3 knots use coeffs=20. If you are using SPLINE fits then you should ensure that the value of TUNE_MAXPOLY is set accordingly, as well as using an appropriate value for TUNE_FFNXPLY and/or TUNE_FFNYPLY.

Initial suggested value: MEAN.

FRAME_CHECK = _LOGICAL

Set FRAME_CHECK if the processed frames are to be checked for bad rows and columns.

The trace frame is checked, and the other frames are assumed to have identical bad row and/or column features.

HARD = _CHAR

If a value for HARD is specified, the plot is written to a file in the format defined by the HARD parameter.

For example, ps_l would generate Landscape format PostScript files.

HELIO_COR = _REAL

The heliocentric correction is applied to the output wavelength-scale of any results files.

Initial suggested value: 0.0.

HI_WAVE = _REAL

The identification of lines proceeds faster for smaller search ranges. Specify the highest wavelength covered by the spectrum. The units in which the wavelength is expressed must be the same as those used in the .ARC line list file. This will normally be Angstroms but may be changed by supplying an appropriate .ARC file.
IDX_NREF_FRAME = _INTEGER

Specifies the number of the arc frame to be processed.

IDX_ parameters provide a method of indexing reduction database arrays by order number and frame number.

A non-zero value for IDX_NREF_FRAME causes processing of the selected frame only.

IDX_NREF_FRAME=0 causes automatic looping through all values for the ‘index’, i.e., processing of all arc frames.

IDX_NUM_ORDERS = _INTEGER

Specifies which order is to be processed.

The IDX_ parameters provide a method of indexing reduction database arrays by order number and frame number.

A non-zero value for IDX_NREF_ORDERS causes processing of the selected order only.

IDX_NREF_ORDERS=0 causes automatic looping through all values for the ‘index’, i.e., processing of all orders.

ID_INTERACTIVE = _LOGICAL

Specifies that interactive arc-line identification is required.

Many options are available in this mode to allow the tuning of the fitted wavelength polynomial, addition and deletion of features etc.

If ID_INTERACTIVE is not set then the echomop will try to identify arc-line features automatically. For orders with enough features (more than 12 lines) this will usually be successful.

A useful strategy is often to do an automatic run first, and then manually examine the fitted features to verify their suitability.

INDIRECT = _CHAR

Internal parameter used to indirect reduction objects to be copied from other reduction databases instead of being calculated (the < function in echomop).
INPTIM = _CHAR

The name of the file holding the frame to be extracted.

This will usually be the Object frame, however the Standard-Star frame may also be extracted. In cases where there are multiple frames of the same Object, then they may each be extracted by re-running this task and specifying a different frame each time (assuming the multiple data frames are perfectly registered).

LOW_WAVE = _REAL

The identification of lines proceeds faster for smaller search ranges. Specify the lowest wavelength covered by the spectrum. The units in which the wavelength is expressed must be the same as those used in the .ARC line list file. This will normally be Angstroms but may be changed by supplying an appropriate .ARC file.
MAX_DISPERSION = _REAL

The range of dispersions to be searched by the automatic line identifier is specified in terms of minimum and maximum Wavelength Unit per-pixel. Care should be taken to ensure that the specified range is wide enough. If in doubt use a larger range than is probably needed. For example, if the actual dispersion is expected to be approx 0.5, then a range of 0.2 to 0.8 would not be inappropriate, whereas a range of 0.4 to 0.6 could possibly be too restrictive. The normal wavelength units will be Angstroms, but alternative units may be used by providing an appropriate .ARC line list.
MIN_DISPERSION = _REAL

The range of dispersions to be searched by the automatic line identifier is specified in terms of minimum and maximum Wavelength Unit per-pixel. Care should be taken to ensure that the specified range is wide enough. If in doubt use a larger range than is probably needed. For example if the actual dispersion is expected to be approx 0.5, then a range of 0.2 to 0.8 would not be inappropriate, whereas a range of 0.4 to 0.6 could possibly be too restrictive. The normal wavelength units will be Angstroms, but alternative units may be used by providing an appropriate .ARC line list.
NREF_FRAME = _INTEGER

The number of wavelength-reference frames to be used.

These will usually be arc spectra. The default is a single frame, but it is possible to use two frames which bracket the object exposure in time. In this case it is assumed that the shift between exposures has been due to smooth variation, an assumption which it is usually not possible to verify.

Note: the names of all frames must be supplied in response to the ARC prompt when locating the reference features. For example:

 ARC=<frame1>,<frame2>

NUM_ORDERS = _INTEGER

Specifies the number of orders present in the frames to be reduced.
OBJFIT = _CHAR

This parameter selects the type of curve fit for object profiling.

The available functions are POLY (the default) and SPLINE.

Note that the required maximum number of coefficients is different in each case. For POLY the maximum number of coefficients corresponds to the number of degrees plus one, so for a cubic use coeffs=4. For a SPLINE the maximum number of coefficients corresponds to 2x(knots+7), so for 3 knots use coeffs=20. If you are using SPLINE fits then you should ensure that the value of TUNE_MAXPOLY is set accordingly, as well as using an appropriate value for TRC_NPOLY.

Initial suggested value: POLY.

OBJ_SKY_GAP = _INTEGER

Parameter is ‘hidden’
OUTPUT_IMAGE = _CHAR

Specifies an output frame (container file name). The frame will contain a full 2-D image array and associated errors if appropriate.
PFL_INTERACT = _LOGICAL

When interactive profiling is selected you can use a graphics cursor to specify the required attributes of each pixel in the spatial profile. The characteristics may be globally applicable, or specified independently for each order. In addition, any polynomial-profile fitting is also performed interactively, with the degree of polynomial and polynomial type adjustable. The fits and residuals at each sub-sample position can be reviewed.
PFL_MODE = _CHAR

The profiling mode is used to specify which profiles are to be calculated/edited.

The options are:

D — Calculate/edit Dekker limits.

O — Calculate/edit Object profile.

S — Calculate Flux standard profile.

A — All, do each of the above in turn.

Normally this parameter would be set to A, and the program run automatically. The profile and calculated limits examined as the program ran, and then re-run interactively with one of the above options.

Some detectors produce many electrons (counts) for each incident photon, or alternatively, one count for many photons. In order to be able to calculate using photon-events it is necessary to take account of this factor. The PHOTON_TO_ADU parameter should be set to the number of incident photons corresponding to each count recorded by the detector.
RBNOBJ = _CHAR

The rebinned image is used to store the distortion-corrected version of the data.

It is only needed in cases of severe geometric distortion and is organised such that pixel columns correspond to linear wavelength bins in a given order.

Some electronic detectors produce a significant amount of noise during the readout process. The older CCDs are often thus afflicted. If a non-zero value is supplied then it will be used to adjust the variances during extraction to take this error into account.
RESULT_FORMAT = _CHAR

Selects the format of the output file.

Options are:

• NDF — Output to the NDF specified by parameter ECH_RDCTN
• ASCII — Output to the specified NDF and to the file specified by ASCII_FILE
• STACK — Output to the DIPSO stack specified by parameter STACK
RESULT_TYPE = _CHAR

Selects the type of data to be saved.

The following types are recognised:

— EXTOBJ, the unscrunched extracted object orders.

— EXTARC, the unscrunched extracted arc orders.

— SCROBJ, the scrunched extracted object orders.

— SCRARC, the scrunched extracted arc orders.

— OSPECT, the merged object spectrum.

The default is EXTOBJ.

SCRUNCH_TYPE = _CHAR

The type of spectrum to be scrunched. This may be one of the following:

— OBJ, the object.

— STAR, the reference star.

— ARC, the arc lamp.

SET_WSCALE = _LOGICAL

This parameter determines the overall type of scrunching to use when scrunching extracted orders. Set to YES if the current frames wavelength range is to be used (all orders) to generate a full range wavelength scale to scrunch into; i.e., all orders are scrunched into the same bin size, but the no of X-axis bins in each order will vary. Set to NO if each order is to be scrunched to its own scale. This retains the X-dimension of the orders, but each order will be scrunched into a slightly different bin size.
SKYFIT = _CHAR

The type of fit to be used for sky-background modelling.

The available functions are MEAN (the default), POLY and SPLINE.

Note that the required maximum number of coefficients for POLY and SPLINE are different. For POLY, the maximum number of coefficients corresponds to the number of degrees plus one, so for a cubic use coeffs=4. For a SPLINE the maximum number of coefficients corresponds to (knots+7)*2, so for 3 knots use coeffs=20. If you are using SPLINE fits then you should ensure that the value of TUNE_MAXPOLY is set accordingly, as well as using an appropriate value for TUNE_SKYPOLY and/or TUNE_SKYXPLY.

Initial suggested value: MEAN.

SLITIM = _CHAR

The frame to be used for determining the limits of the dekker.

This should be a frame which clearly delineates the inter-order gap and the full extent of the slit. In general the arc-lamp frame is used, but a flat-field may also work.

SOFT = _CHAR

If SOFT is specified, the plot is written to the device defined as the current softcopy device.
STACK = _CHAR

Name of the DIPSO stack to save data to.

The ’_STK.sdf’ part of the filename should not be given.

The default value is ECHOMOP.

START_WAVE = _REAL

This parameter is only used when a user-specified wavelength scale is being generated (BIN_SIZE>0). It specifies the start wavelength for the re-binned wavelength scale. The default is to calculate the start wavelength from the fitted wavelength scale if no value is supplied using this parameter.

Initial suggested value: 0.0.

TRACE_MODE = _CHAR

The type of tracing method to be used.

The following options are available:

U — indicates (ICUR) coordinates are supplied.
R — selects re-tracing using old trace as baseline.
T — indicates that a triangle filter is to be applied before centre location.
A — indicates that in cases of failure, the program is to automatically fall-back to the next-least demanding centering mode.

Plus one of the following mandatory selections:

B — basic, simple-minded centre of gravity.
E — locate profile edges and interpolate.
C — find centroid of profile.
G — fit a Gaussian across profile.

For example:

TAG — would fit Gaussians to triangle-filtered data and automatically fall-back to try centroiding for problem samples.
B — would do simple centre-of-gravity calculations on the raw profile, with no automatic fallback being used.

The default mode is C which provides a reasonable balance of probability-of-a-good-trace vs. time-taken. The order of specification is significant and must obey the following rules:

— Optional U or R followed by

— Optional T and/or A followed by

— One of B, E, C or G.

TRACIM = _CHAR

The name of the file containing a frame to be used for the tracing of the orders. Tracing may be attempted using a wide variety of data frame types. If the object frame has a good signal-to-noise ratio then this should be used. In cases where the object is faint, or exhibits large-scale absorption features, then either the flat-field or flux-calibration reference frame should be used.
TRCFIT = _CHAR

This parameter selects the type of line fit for order tracing.

The available functions are POLY (the default) and SPLINE.

Note that the required maximum number of coefficients is different in each case. For POLY the maximum number of coefficients corresponds to the number of degrees plus one, so for a cubic use coeffs=4. For a SPLINE the maximum number of coefficients corresponds to 2x(knots+7), so for 3 knots use coeffs=20. If you are using SPLINE fits then you should ensure that the value of TUNE_MAXPOLY is set accordingly, as well as using an appropriate value for TRC_NPOLY.

Initial suggested value: POLY.

TRC_INTERACT = _LOGICAL

Determines whether order fitting/clipping is interactive.

Set for interactive order fitting/clipping.

If not set, order fitting/clipping proceeds automatically. When automatic fitting is engaged there are two parameters which may be adjusted to optimise the performance of the program. These are: TUNE_CLPMXDEV, which defines the clipping point, and TUNE_CLPBY, which is the number of points to clip in each iteration.

The default value is NO.

TRC_NPOLY = _INTEGER

The default number of coefficients to be used when fitting functions to the order trace.

The type of function to be used is set using the parameter TRCFIT. (Default value is POLY for polynomial.)

When TRCFIT=POLY then the number of coefficients should be set to degree of polynomial + 1.

When TRCFIT=SPLINE the number of coefficients should be set to 2x(number of knots + 7).

For example, setting TRC_NPOLY to 4 would permit the fitting of polynomials of the form:

constant + ax + bx squared + cx cubed Initial suggested value: 4.

TRC_VETO = _LOGICAL

Set to YES if the order consistency is to be checked interactively. Automatic checking is performed otherwise.

When automatic checking is engaged there are two parameters which may be adjusted to optimise the performance of the program.

These are TUNE_CLPMXDEV which defines the clipping point, and TUNE_CLPBY which is the number of points to clip in each iteration.

When TRC_VETO is set, the option to reject a re-fitted order at each iteration is available.

It is strongly recommended that this option is not used until you have a clear understanding of the algorithm used by the consistency checker, as it is possible to ‘drive’ the fit off by injudicious rejection of the re-fits proposed by the program.

TUNE_AAACODE = _INTEGER

Used only when the program is making use of the Astronomy & Astrophysics Abstracts system of information categorisation (TUNE_USEAAA=YES). This system consists of a set of numbers corresponding to topics in Astronomy. TUNE_AAACODE is used to supply an AAA standard information category for the data being reduced. These parameters are only used in conjunction with the archiving facility, when TUNE_ARCHIVE=YES.

Initial suggested value: 1.

TUNE_AIRTOVAC = _LOGICAL

Determines whether the wavelength scales in output datafiles are converted from air to to vacuum wavelengths.

If set to YES, then the vacuum wavelengths are converted using the procedure:

$\begin{array}{rcll}wavm& =& {\left(ol{d}_{wavelength}×1{0}^{-4}\right)}^{-2}& \text{}\\ sum& =& 64.328+29498.1/\left(146.0-wavm\right)+255.4/\left(41.0-wavm\right)& \text{}\\ ne{w}_{wavelength}& =& ol{d}_{wavelength}×\left(1.0+1{0}^{-4}×sum\right)& \text{}\end{array}$

Only the wavelength scales in the output file are effected; the reduction database wavelength scales remain unchanged.

Initial suggested value: NO.

TUNE_ARCHIVE = _LOGICAL

Set to YES if automatic archiving of results files is to be performed. The archive is maintained by a central site and will support query facilities. A 2-year data protection scheme is applied, so your spectra may not be accessed by other parties until 2 years after its inclusion in the archive. See HELP ECHOMOP ARCHIVING for a more detailed discussion.

The default value is NO.

TUNE_AUTLOC = _LOGICAL

Set this parameter if the positions of the orders are to be determined automatically.

When not set, the program allows interactive selection of the order centres on a graphic display. This is useful if you wish to select a subset of the available orders in the frame, or to review the order centres found by the program.

The default value is NO.

TUNE_AUTOMATE = _CHAR

This hidden parameter allows multiple options to be automatically invoked upon startup of the monolithic task.

Any options required must be supplied on the command line or the you will be prompted as usual. For example:

 TUNE_AUTOMATE=1,2,3,EXIT

would run the first 3 processing options and then exit.

If EXIT is not given as an option, echomop will start the menu task ECHMENU when the list of options specified by TUNE_AUTOMATE has been exhausted.

TUNE_BATCH = _LOGICAL

Set to YES for batch-mode operation.
TUNE_BLZRSET = _LOGICAL

This parameter controls whether or not the blaze function is to be reset to unity after being applied. The default is to do so, thus protecting against accidental re-application of the blaze function to an extracted spectrum. In some cases it may be required to keep the blaze function and apply it to a number of extracted object spectra. In this case the TUNE_BLZRSET=NO setting should be used.

The default value is YES.

Initial suggested value: YES.

TUNE_CLONE = _CHAR

The reduction database from which to clone information.

The reduction database should have been created by echomop previously. Objects which would normally be calculated by echomop will instead be copied from the named file. This allows the cloning of sections of a reduction amongst multi-frame datasets.

TUNE_CLPBY = _INTEGER

This parameter sets the number of points automatically clipped per order-trace fit/clip iteration.

The TUNE_CLPBY most-deviant points are clipped before a re-fit is attempted, this process is then repeated until either: all points have deviations of less than TUNE_CLPMXDEV from the polynomial; or, so many points have been clipped that a meaningful fit can no longer be attempted. In the latter case the order will be automatically disabled. You may manually re-fit the trace if the order is still to be processed.

The default value is 1.

TUNE_CLPMXDEV = _REAL

The maximum deviation used when automatically clipping traced points to fit order tracing polynomials.

It is expressed in units of pixels and will usually be a fraction of a pixel.

Any traced point which is further than this limit from the fitted polynomial (for that X-coordinate) is liable to be clipped. Automatic clipping only stops when either all points have deviations of less than TUNE_CLPMXDEV from the polynomial; or when so many points have been clipped that a meaningful fit can no longer be attempted. In this latter case, the order will be automatically disabled. You may re-fit manually if the order is still to be processed.

The default value is 0.5.

TUNE_CNSDEV = _REAL

Specifies the threshold for deciding whether the values generated by the order specific polynomial and the all-order polynomial, are consistent at a particular increment. TUNE_CNSDEV is the maximum difference between the two (in pixels) which is accepted as consistent.

The default value is 0.5 pixels.

TUNE_CRCLEAN = _LOGICAL

When set to YES then the optimal extraction will attempt to identify cosmic rays by examining the local variance. This option will only function when full optimal extraction has been selected using EXTRACT_MODE=O. It will not normally be used as more flexible tasks for cosmic-ray removal are provided as separate programs. See HELP ECH_DECOSMIC.
TUNE_CRINTER = _LOGICAL

Determines how cosmic-ray-contaminated pixels are to be treated. (Only used when cosmic-ray checking is enabled by TUNE_CRTRC=YES.)

When set, cosmic-ray pixels are replaced in the output image by interpolated values.

When not set, cosmic-ray pixels are marked with a flag value.

The default is NO.

TUNE_CRMAX = _INTEGER

The number of pixels expected to be contaminated by cosmic rays. (Only used when cosmic-ray checking is enabled by TUNE_CRTRC=YES.)

You may use an estimate, or else a value can be generated by an automatic modeller.

If no estimate is available, then zero should be used. The program will then display a histogram of the ratio of original divided-by median image and allow manual selection of a clipping point. The number of pixels to be clipped (flagged as cosmic rays) will then be shown.

TUNE_CRTRC = _LOGICAL

Set if the trace frame is to be checked for possible cosmic-ray contamination.

This will not usually be necessary and is provided for the case where only a faint, contaminated object frame is available for order tracing.

Initial suggested value: NO.

TUNE_CRXBOX = _INTEGER

X-dimension of the area used to calculate median values.
TUNE_CRYBOX = _INTEGER

Y-dimension of the area used to calculate median values.
TUNE_DB_SCOPE = _INTEGER

This parameter sets the number of nearest-neighbours to take account of when constructing/using a reference feature database (FDB). It will not normally require adjusting unless a very odd line list is being used.
TUNE_DEKABV = _INTEGER

This parameter sets the upper extraction limit for the dekker in the spatial direction.

A non-zero value for this parameter will over-ride the automatic dekker extent calculated by ech_spatial.

TUNE_DEKABV can be used when the dekker extent and position relative to the order traces are well known. Typically, it will be used when the first of a set of similar frames has been manually extracted and automation of the extraction of the remaining frames is required.

Initial suggested value: 0.

TUNE_DEKBLW = _INTEGER

This parameter sets the lower extraction limit for the dekker in the spatial direction.

A non-zero value for this parameter will over-ride the automatic dekker extent calculated by ech_spatial.

TUNE_DEKBLW can be used when the dekker extent and position relative to the order traces are well known. Typically, it will be used when the first of a set of similar frames has been manually extracted and automation of the extraction of the remaining frames is required.

Initial suggested value: 0.

TUNE_DEKTHR = _REAL

The threshold level for automatic determination of the dekker extent.

This is the percentage (of maximum intensity) below which the spatial profile is to fall before being classified as outside the dekker. In general an Arc frame will be used to establish the dekker limits, and a value of 80% will suffice.

The default value is 0.8 (i.e. 80%).

TUNE_DIAGNOSE = _LOGICAL

This parameter should be set only for a short period when a problem has occurred (and can be reproduced). It enables the production of a log file containing detailed information of use to the maintainer of ECHOMOP. This log is stored in the file echomop_diagnostics.log.

In the event of a problem mail this file, with details of the problem, to the Starlink Software Librarian at: starlink@jiscmail.ac.uk.

TUNE_DPRBTHR = _REAL

The maximum difference between observed and theoretical (based on observed mean, sigma) CDF’s is calculated. The Kolmogorov-Smirnov test is used to evaluate the probability that the measured deviation is a chance occurrence (i.e. that the two distributions are actually the same). In general any significant probability indicates that the two distributions compare very well. When the K-S probability exceeds the TUNE_DPRBTHR threshold, clipping stops and the fit is accepted.

The default value is 0.9 (i.e. 90%).

TUNE_DSGMTHR = _REAL

The sigma clipping threshold for deciding which pixels to clip at each iteration of CDF matching, is set by this parameter. Normally clipping should be set to 2 to 3 sigma. At each iteration the deviation of each pixel from its predicted value is evaluated in terms of the mean and sigma for all pixels (per-order basis).
TUNE_FCHECK = _LOGICAL

Set this parameter if the processed frames are to be checked for ‘bad’ row and/or columns.

The trace frame is checked and other frames are then assumed to have identical ‘bad’ features.

TUNE_FFINTER = _LOGICAL

Set this parameter if the degree of polynomial used to model the flat field is to be under interactive control.
TUNE_FFLMED = _LOGICAL

Whether the median is to be used when calculating the behaviour of the flat field using only local pixels.

Set if the median value is to be used.

This applies only when TUNE_FFNXPLY=1 (no polynomial model), in which case the local median or mean is taken over the nearest TUNE_FFLSMP pixels. This is useful for cases where there is significant small-scale structure in the flat field.

Initial suggested value: NO.

TUNE_FFLSMP = _INTEGER

The number of samples per point to use when the flat-field model is based on the local behaviour only.

This parameter is only used when the X-polynomial degree, TUNE_FFNXPLY=1, which implies a constant flat field.

The parameter TUNE_FFLMED controls whether a local mean or median value is used.

Initial suggested value: 10.

TUNE_FFNXPLY = _INTEGER

Specifies the number of polynomial coefficients in X for the flat-field model, and the re-fitted model.

A model of the flat field is made by fitting a polynomial at each X- and Y-increment. These polynomials are then used to calculate the balance factors at the ’Object’ pixel positions.

Note: If the parameter is set to zero then no modelling in the X-direction will be performed. If the parameter is set to 1, then no polynomials are used (they would be constant), but the balance factors are calculated using the local mean value based on a TUNE_FFLSMP pixel sample. This option should be used when under-sampling etc. is preventing the fitting of polynomials at all.

The default value is 1.

TUNE_FFNXREJ = _INTEGER

Specifies the number of clip/reject/remodel cycles in X (dispersion direction) flat-field modelling.

The model of the flat field is made by fitting a polynomial at each X- and Y-increment. These polynomials are then used to calculate the balance factors at the ’Object’ pixel positions.

TUNE_FFNYPLY = _INTEGER

Specifies the number of polynomial coefficients in Y for the flat-field model, and the re-fitted model.

The model of the flat field is made by fitting a polynomial at each X- and Y-increment. These polynomials are then used to calculate the balance factors at the ’Object’ pixel positions.

The default value is 0.

TUNE_FFNYREJ = _INTEGER

Specifies the number of clip/reject/remodel cycles in Y (dispersion direction) flat-field modelling.

The model of the flat field is made by fitting a polynomial at each X- and Y-increment. These polynomials are then used to calculate the balance factors at the ’Object’ pixel positions.

TUNE_FFSUBSMP = _LOGICAL

Whether subsampling is to be used when doing X-polynomial fits.

Set if subsampling is to be done.

This parameter is only used when polynomial fitting in the X-direction is enabled (by setting TUNE_FFNXPLY>1) and causes the program to subsample (10 samples per-pixel) the spatial profile during fitting. This is useful when the balance factors ‘outside’ the dekker, or at the very edge of the dekker (where the intensity changes quickly from pixel-to-pixel) are needed.

Initial suggested value: NO.

TUNE_FFTHRESH = _REAL

Specifies the rejection threshold for the flat field.

Any pixels which deviate by more than TUNE_FFTHRESH sigma from the fitted polynomial model will be clipped and the model re-fitted.

The polynomial model of the flat field is made by fitting a polynomial at each X- and Y-increment. These polynomials are then used to calculate the balance factors at ’Object’ pixel positions.

The default value is 10.0 sigma.

TUNE_FIBRES = _LOGICAL

Set to YES if a multi-fibre object frame.
TUNE_FINCPLY = _INTEGER

The number of polynomial coefficients to be used for fitting each individual increment. Increments consist of all pixels at a specific distance above/ below the order trace. Polynomials are fitted through each increment in turn, object or sky.
TUNE_FLUX = _LOGICAL

YES if the program is to conserve flux. If not set, it will maintain the mean height of the data.
TUNE_HELIO = _INTEGER

Parameter is ‘hidden’
TUNE_IDINMN = _INTEGER

Specifies the minimum number of features to be used when generating ratios for initial identification. In general, a good solution can be found using only the strongest 8-16 features. The program slowly increases the number of features it uses until an adequate solution is found. In cases where the orders are distorted it may be advantageous to increase the minimum number of features to cover the majority of located features.

Initial suggested value: 8.

TUNE_IDINMX = _INTEGER

Specifies the maximum number of features to be used when generating ratios for initial identification. In general, a good solution can be found using only the strongest 8-16 features. The program slowly increases the number of features it uses until an adequate solution is found. However, there may be large numbers of weak features present which are not in the reference database. This parameter allows the setting of an absolute maximum on the number of features (per order) which are to be considered.

Initial suggested value: 30.

TUNE_IDMDLT = _INTEGER

Specifies the maximum number of neighbouring features (on EACH side) to examine when generating ratios for matching. Increasing this will lead to exponential increases in CPU time, so it should be used with caution when all else fails.

The default value is 6.

TUNE_IDMXDIF = _REAL

Specifies the maximum difference between the ratios derived from observed features, and those in the database with which a match is attempted. The difference is evaluated by calculating

giving a fractional measure of the difference. For example: difference=0.01 indicates that the two quantities differ by approximately 1% of their average magnitude. Values much larger than 0.1 are likely to generate a lot of coincidence matches; values less than 0.01 may well miss ‘good’ matches in less-than-ideal data.

The default value is 0.03.

TUNE_IDSDLT = _INTEGER

Specifies the starting number of neighbouring features (on each side) to examine when generating ratios for matching. Increasing this will lead to exponential increases in CPU time, so it should be used with caution when all else fails.

Higher values are tried automatically by the program if no solution can be found. The number of neighbours considered is increased monotonically until it reaches the maximum of TUNE_IDMDLT, when the program gives up.

The default value is 3.

TUNE_IDSTRNG = _REAL

Specifies the minimum strength of features to be used for initial identification. It is specified by relating the strength of a feature to that of the strongest feature present in that order. Any features of strength max/TUNE_IDSTRNG or greater, will be included in the initial set.

The default value is 10.0, thus all features which are at least one tenth as strong of the strongest feature will be eligible for identification.

TUNE_INTR = _LOGICAL

Selects linear interpolation when re-binning.
TUNE_IUE = _INTEGER

Non-zero if IUE type data frame.
TUNE_LOG = _LOGICAL

Used only when TUNE_SCRMODE=1, and indicates that the output wavelength scale has bins which vary on a LOG scale.
TUNE_MAX2DPLY = _INTEGER

Maximum number of coefficients for 2-D fits.
TUNE_MAX2DPNTS = _INTEGER

Maximum number of data points to be used in 2-D fits.
TUNE_MAXLINES = _INTEGER

Maximum number of arc-line slots.
TUNE_MAXPOLY = _INTEGER

The maximum number of polynomial coefficients to be allowed for the duration of this reduction.

For POLY trace fits, the order of the polynomials used for each fit may be varied up to this limit, but may not be set to higher values.

For SPLINE trace fits this is the maximum number of fit parameters which can be used. A high vale may be needed. The number of parameters required is 2x(knots+7).

The default value is 50, which should be acceptable in most cases.

TUNE_MAXRFLN = _INTEGER

Set to the maximum number of reference lines per order which are allowed. This parameter is used to dimension objects in the reduction database and should not normally need to be altered. You may feel tempted to lower it to avoid the seeming profusion of ‘false’ line candidates produced by ech_linloc. This is not a good idea if the automatic line-identification mode is being used as it requires the presence of faint feature positions for reliable operation.
TUNE_MERGE = _LOGICAL

Set to YES if the scrunched object spectrum is to be merged into the 1-D spectrum. The default is to zero the 1-D spectrum before output. Setting TUNE_MERGE=YES allows the spectra from multiple frames to be co-added into the same output spectrum using a weighted merge.

The algorithm is the same as used in the fiGARO ECHMERGE program.

Initial suggested value: NO

TUNE_MINCR = _REAL

Specifies the threshold level for deciding whether pixels located as ‘possibly cosmic-ray-contaminated’ should be flagged as such.

Only those pixels with intensities greater than TUNE_MINCR will be flagged. This provides a limit for the case where a cosmic-ray identifier becomes over enthusiastic due to the nature of the frame.

Normally this parameter should be set to zero, and therefore, have no effect.

Initial suggested value: 0.0.

TUNE_MRGMAXX = _INTEGER

Number of rhs pixels to ignore.
TUNE_MRGMINX = _INTEGER

Number of lhs pixels to ignore.
TUNE_MRGWGHT = _CHAR

Type of weighting to use for merge.

The maximum number of consecutive bad samples permitted before abandoning an order trace.

The default value is 10.

TUNE_MXSKYPIX = _INTEGER

The maximum number of pixels allowed in the spatial direction for each order.

This parameter is used to dimension objects in the reduction database and should only need to be altered when dealing with objects where the spatial extent is large.

Note that increasing this parameter leads to a substantial increase in the size of a reduction database, so it should be set to as small a value as sensible for your data.

TUNE_MXSMP = _INTEGER

The maximum number of independent X-samples to use when tracing an order.

If the X-dimension is less then 500 every X-increment will be sampled.

The default value is 500.

TUNE_NOARC = _LOGICAL

Set to YES if there is no arc frame to use for wavelength calibration. This may also be specified by replying NONE when prompted for the name of the arc frame.

Initial suggested value: NO.

TUNE_NOFLAT = _LOGICAL

Set this parameter if there is no flat-field frame to use for balance-factor calculation.

This may also be setting the parameter FFIELD to NONE when prompted for the name of the flat-field frame.

In the absence of a flat-field frame, all balance factors are set to unity.

Initial suggested value: NO.

TUNE_OBJABV = _INTEGER

This parameter sets the upper extraction limit for the object in the spatial direction.

A non-zero value for this parameter will over-ride the automatic object extent calculated by ech_spatial.

TUNE_OBJABV can be used when the object extent and position relative to the order traces are well known. Typically, it will be used when the first of a set of similar frames has been manually extracted and automation of the extraction of the remaining frames is required.

Initial suggested value: 0.

TUNE_OBJBLW = _INTEGER

This parameter sets the lower extraction limit for the object in the spatial direction.

A non-zero value for this parameter will over-ride the automatic object extent calculated by ech_spatial.

TUNE_OBJBLW can be used when the object extent and position relative to the order traces is well known. Typically, it will be used when the first of a set of similar frames has been manually extracted and automation of the extraction of the remaining frames is required.

Initial suggested value: 0.

TUNE_OBJPOLY = _INTEGER

Specifies the degree of polynomial to use when trying to fit to the object intensity at any single X/lambda increment. The normal mode of operation for extraction is to form a model of the profile by averaging subsamples from all orders. The polynomial model (per increment) should only be used when the profile varies markedly along an order due to atmospheric or instrumental peculiarities.

The default value is 0.

TUNE_OBJREJ = _INTEGER

Specifies the number of reject cycles for which object profile samples will be clipped, and the model re-fitted.

The polynomial model of the object’s spatial profile is made by fitting a polynomial at each X-sample. These polynomials are then used to estimate the profile at each spatial sample of the object.

TUNE_OBJRTHR = _REAL

Specifies the reject-threshold for object pixels.

Any pixels which deviate by more than TUNE_OBJRTHR sigma from the fitted polynomial model, will be clipped, and the model re-fitted. The polynomial model of the object profile is made by fitting a polynomial at each X-increment. These polynomials are then used to estimate the signal at each spatial sample of the object.

Initial suggested value: 5.0.

TUNE_PAGE = _INTEGER

This parameter specifies the number of lines on the terminal screen.

When set to a non-zero value, after each TUNE_PAGE lines of non-menu output the program will pause and wait for a key to be hit before continuing. A variety of options are available at this point:

 D,d,uparrow,KP8,p,P,b,B Scroll back one line. U,u,downarrow,KP2,f,F,n,N Scroll forward a line. space Resume output. return Output next line only. pageup Previous full screen. pagedown Next full screen.

The program maintains a buffer of lines output to the screen; you may move around using the keys mentioned above. Only the space or return keys will resume regular program output. If the parameter value is not positive then no paging is done.

Initial suggested value: 0.

TUNE_PARTORD = _LOGICAL

Set this parameter if the program is to make use of order slope and inter-order distance data to look for partial orders at the top and bottom of the trace frame.

The default value is NO.

TUNE_PFLSSAMP = _INTEGER

The maximum number of subsamples used when determining the subsampling rate to be used for the generation of the averaged profile.

This parameter should only need to be changed when processing frames with a very large number of pixels sampling the object in the spatial direction.

The default value is 301 subsamples, which will normally be more than is needed.

TUNE_PFSAMP = _INTEGER

The maximum number of profile subsamples.

The default value is 101.

TUNE_PREBAL = _LOGICAL

Set this parameter if the flat-field frame supplied has already been pre-processed to contain balance factors for the pixel-to-pixel variations.

If set, the modelling will not take place and the balance factors will simply be copied from the supplied frame. This should be used for cases where the polynomial model cannot generate appropriate values.

Note: The removal of the blaze function is a separate operation and will require the use of the original raw flat-field frame (or equivalent).

Selects quadratic interpolation when re-binning. This is usually more accurate than linear interpolation.

The default value is YES.

TUNE_QUICK = _LOGICAL

Set if data are to be processed in quick-look mode.

This enables fast reduction by automatically tailoring parameters. In particular: all fits are clipped automatically; no flat fielding is performed; and a simple summed extraction is used.

Prior to quick-look extractions the object extent should be specified by the parameters TUNE_OBJBLW and TUNE_OBJABV.

Initial suggested value: NO.

TUNE_REPORT = _CHAR

This parameter is used to control the variety of reporting output by the program.

It will usually be left blank to indicate default reporting to the terminal/batch log file. Options include:

 F Specifies full reporting of task/module entry. L Specifies duplicate log of reports to disk file (ech_report.log in the current directory). B Brief reporting, task starts only. S Silent, no terminal reports at all. E Error reports to override other setting (BS). P Print log file on completion (only with L).

Specifiers may be concatenated in any order, thus

 BELP

would specify minimal reporting, except for task startup and error reports. Reports to be copied to a log file and printed upon completion.

Initial suggested value: ’ ’.

TUNE_REVCHK = _LOGICAL

Normally the arc line identification task assumes that wavelength increases from left to right (increasing X-coordinate). If you are in the unfortunate position of not being sure that this is the case then setting this parameter will cause the program to check both possible orientations. TUNE_REVCHK=YES will take twice as much time as TUNE_REVCHK=NO.

The default value is NO.

TUNE_RFLNTHR = _REAL

Specifies the degree to which arc line features are required to exceed the continuum intensity before they are considered as valid features. The default value of 1.25 is deliberately set low to allow the automatic line identifier access to very faint features. This parameter should not need adjusting unless the arc spectrum has a difficult continuum or other special problems associated with it. The line identification task provides interactive control over the minimum intensity for ‘fitted’ features via its (T)hreshold option.

The default value is 1.25.

TUNE_SATRTN = _REAL

Specifies the threshold level for deciding whether any pixels should be flagged as saturated.

Flagged pixels do not contribute to the extraction in any way. Only pixels with intensities less than the TUNE_SATRTN level will be used by subsequent tasks.

Initial suggested value: 1.0E20.

TUNE_SCFRACT = _REAL

Specifies the mixing fraction for two wavelength ranges (fitted). This is only required when there is a ‘before’ and an ‘after’ arc frame, and there has been significant movement of the image in between the two. The fraction is used as follows:
$\lambda ={\lambda }_{1}+\left({\lambda }_{2}-{\lambda }_{1}\right)×Fraction.$

No facility is provided for calculating the appropriate fraction but it will usually be estimated as the the ratio of elapsed times between the object frame, and the before/after arc frames (assumes a constant ‘drift’ of the instrumental setup).

Used only when TUNE_SCRMODE=0, and indicates the number of input bins to be added into each output bin. This is used mainly to increase the S/N of a weak spectrum, at the expense of resolution.
TUNE_SCRMODE = _INTEGER

If equal to zero, selects mode 0, in which input bins can be grouped and shifted to form the output bins. (See also TUNE_SCRADD).

If not equal to zero, selects mode 1, in which the input bins are transferred to the output bins in accordance with the wavelength scale(s).

TUNE_SKEW = _REAL

The number of bins the input array is to shifted (in mode 0 only). A positive value shifts data to higher pixel numbers - this is a fiGARO convention, and is the opposite of that used by Lolita.
TUNE_SKVRCORR = _LOGICAL

When this parameter is set to YES then weights are modified to include uncertainty in sky fit optimal variances equivalent to maximising:
$\frac{\sum _{i}{W}_{i}^{2}{V}_{i}+\sum _{i,j}{W}_{i}{W}_{j}{V}_{ij}}{{\left(\sum _{i}{W}_{i}{F}_{i}\right)}^{2}}$

where:

${W}_{i}$ is the weight on pixel $i$,

${V}_{i}$ is the variance on the value of pixel $i$,

${V}_{ij}$ is the covariance of the skyfit between pixels $i$ and $j$,

${F}_{i}$ is the normalised profile at pixel $i$.

This reduces to solving:

${A}_{ij}{W}_{j}={F}_{i}$

where:

${A}_{ij}={V}_{ij}$ for $i\ne j$, and

${A}_{ii}={V}_{i}+{V}_{ij}$.

TUNE_SKYHILIM = _REAL

Specifies the upper threshold used when automatically determining the location of ‘sky’ pixels in the object spatial profile.

The algorithm used is:

— Median filter profile and multiply by 1.05

— Calculate the threshold point: Min + (Max-Min) x TUNE_SKYHILIM

— Take the minimum of the two quantities

This minimum is used as the maximum sky intensity allowed along the spatial profile.

The default value is 0.5 (i.e. 50%).

TUNE_SKYINTER = _LOGICAL

Set if the modelling of sky backgrounds is to be under interactive control.
TUNE_SKYLINW = _INTEGER

Specifies the maximum expected width of sky lines in pixels.

This is only used when a wavelength-dependent model is being used to predict sky intensities using whole-order polynomials. In this case, any pixel whose intensity differs from the fit by more than sigma TUNE_SKYLTHR will be treated as a sky-line candidate, and its actual intensity entered into the model in place of the fit prediction. The same procedure is also applied to the pixels’ TUNE_SKYLINW nearest neighbours to ensure that the entire sky line is entered into the model even when its wings are within the sigma constraint described above. This parameter only has effect when TUNE_SKYXPLY>0.

The default value is 5 pixels.

TUNE_SKYLTHR = _REAL

Specifies the threshold level for the treatment of sky-line candidates in the wavelength-dependent sky model produced when TUNE_SKYXPLY is greater than zero.

In this case, any pixel whose intensity differs from the fit by more than TUNE_SKYLTHR x fit-sigma will be treated as a sky-line candidate, and its actual intensity entered into the model in place of the prediction. The same procedure is also applied to the pixels TUNE_SKYLINW nearest neighbours to ensure that the entire sky line is entered into the model even when its wings are within the sigma constraint described above.

Initial suggested value: 3.0.

TUNE_SKYPOLY = _INTEGER

When TUNE_SKYPOLY>0 it specifies the degree of polynomial to use when trying to fit to the sky intensity at any single constant-X / lambda increment. These polynomials are used to predict the contributory sky intensity in the object pixels.

The default value is TUNE_SKYPOLY=0 to obtain sky averaging (i.e., sky model is constant at each order/column).

Set TUNE_SKYPOLY=-1 when there is no sky to be modelled (i.e., sky model is zero everywhere).

Initial suggested value: 0.

TUNE_SKYREJ = _INTEGER

Specifies the number of reject cycles for which sky will be clipped, and the model re-fitted. The polynomial model of the sky background is made by fitting a polynomial at each X-increment. These polynomials are then used to estimate the sky level at the positions of the ‘Object’ pixels.
TUNE_SKYRTHR = _REAL

Specifies the reject-threshold for sky pixels. Any sky pixels which deviate by more than TUNE_SKYRTHR sigma from the fitted polynomial model, will be clipped, and the model re-fitted. The polynomial model of the sky background is made by fitting a polynomial at each X-increment. These polynomials are then used to estimate the sky level at the positions of the ‘Object’ pixels.

Initial suggested value: 5.0.

TUNE_SKYSIM = _LOGICAL

Set to YES if simulations are to be used to estimate the variance of the sky using polynomial fits in the wavelength direction.

These simulations are CPU intensive.

The default value is NO.

TUNE_SKYXPLY = _INTEGER

Specifies the degree of polynomial to use when trying to fit to the sky intensity over the whole order at a spatial increment.

This facility will be most useful when the sky is very uniform, or possibly when trying to model the scattered light in the inter-order region. The intensities predicted by the wavelength-dependent model are used as input to the spatial model only when they fall within a user-defined distance from the observed value, and when they are not possible sky-line features.

The default value is 0.

TUNE_TRCNS = _REAL

Specifies the degree to which traces may be inconsistent. Expressed as a percentage of X-samples. For example, if a trace may be a maximum of 10% inconsistent, measured against the other traces, then TUNE_TRCNS should be set to 0.1.

The default value is 0.05.

TUNE_TWTHR = _REAL

The ’trace-width-threshold’ is provided for cases when the S/N of the frame being examined to locate the orders is very low.

The threshold is the degree to which off-trace pixels must fall below the pixel at trace centre (in the spatial direction) in order to be considered as ’off-order’. I.e., the trace width is estimated by stepping pixel-by-pixel above and below the trace until the intensity falls below (1.0 - TUNE_TWTHR) x intensity-at-trace-centre.

The default value is 0.95 (95%).

TUNE_UHRF = _LOGICAL

Set if the data is from the UHRF (Ultra-high Resolution Facility of the UCLES).
TUNE_USEAAA = _LOGICAL

Set to YES if the program is to make use of the ‘Astronomy & Astrophysics Abstracts’ system of information categorisation. This consists of a set of numbers corresponding to topics in Astronomy. If TUNE_USEAAA is active then you will be shown the currently recognised categories and asked to select the one most relevant to the data being reduced. This parameter is only used in conjunction with the archiving facility, when TUNE_ARCHIVE=YES. The prompting process may be overridden by supplying a valid AAA code using the parameter TUNE_AAACODE.

Initial suggested value: YES.

TUNE_USE_NXF = _REAL

Specifies the fraction of the X-dimension of the frame to be used for determining the profiles.

This is set low (0.2=20%) by default for speed.

Very poor data may benefit from an increase in this parameter, which provides a more accurate sampling of the object profile, and thus more accurate extraction weights. The central fraction from each order is sampled and the average profile over all orders is calculated.

A special mode is selected by setting TUNE_USE_NXF>=1, which makes the sampling independent for each order. In this case the fraction of the X-dimension of the frame used is TUNE_USE_NXF-1, for example, TUNE_USE_NXF=1.2 would select individual-order profiling using 20% of each order.

The default value is 0.2 (i.e. 20%).

TUNE_XBOX = _INTEGER

This parameter allows the sampling size (in X-pixels) used when performing order location to be altered.

This should be necessary when only one frame is available for tracing the orders, and this frame is of poor quality.

Some care must be taken to ensure that the sampling box is kept sufficiently small that all samples come from the same order for each sampling-box position.

TUNE_XZONE = _INTEGER

Number of horizontal image zones.
TUNE_YBLAZE = _LOGICAL

Set to YES if automatic Y-blaze correction is to be used. This correction works by examining the scrunched orders and re-scaling them so that the extremes of adjacent orders match up. This should only be used when no flux calibration is available and there is a real need for it. It requires that the blaze fit be scrunched before being applied and therefore necessitates a blaze-fit followed by the scrunch option. The blaze correction is only applied to scrunched (and merged) orders in this case. When disabled then blaze fitting is applied to the extracted orders directly and these may be scrunched later if required.

Initial suggested value: NO.

TUNE_YZONE = _INTEGER

Number of vertical image zones.
USE_MEDIAN = _LOGICAL

YES if median is to be used.
WAVFIT = _CHAR

Specifies the wavelength fitting function to use.
W_NPOLY = _INTEGER

Number of coefficients of wavelength fitting function.
W2_NX_POLY = _INTEGER

Maximum order of 2-D X-axis polynomial.
W2_NY_POLY = _INTEGER

Maximum order of 2-D Y-axis polynomial.
2D_INTERACT = _LOGICAL

Set to YES if you want to interactively control the 2-D polynomial fitting of the distortion corrections. Polynomials are fitted in two perpendicular directions (rows and columns) and generate the point-to-point predicted deviation from wavelength fit for each pixel centre. Interactive operation allows you to view an exaggerated version of the fitted points, and to selectively clip points on the basis of their deviations from the fit.