ECHSELECT-Interactive selection of sky and object spectra for an echelle

Description:

ECHSELECT allows the user to indicate interactively the cross-sections of a corrected echellogram (one straightened by CDIST for example) to be used as object and sky for the various orders. It then creates a collapsed echellogram for the object orders, and (optionally) one for the sky orders.

Parameters:

IMAGE

IMAGE is used to specify the corrected echellogram to be processed by ECHSELECT. It should have its orders straight and parallel to the x-axis (i.e. as processed by CDIST).

PREVIOUS

If PREVIOUS is selected, the results of a previous selection are read from a file called ECHSELECT.LIS in the default directory and may be modified. Otherwise, you start from a clean slate. Note that this allows you to apply a selection based on one image to data in another - for example you can process an arc according to the selection made using an associated object exposure.

WHOLE

ECHSELECT gets you to select cross-sections by indicating them on a plot of a 1-D cut through the original image. This cut is orthogonal to the wavelength direction, so the various orders should show up as peaks in the plot. Often, the ends of the image have odd effects and should not be included in this cut. If you want to specify the limits of the plot explicitly, set WHOLE to NO. Otherwise the whole image will be summed to produce the cut.

XSTART

If WHOLE is not selected, XSTART gives the x-axis value for the first of the cross-sections to be summed to give the cut through the image

XEND

If WHOLE is not selected, XEND gives the x-axis value for the last of the cross-sections to be summed to give the cut through the image

MSTART

This is the order number of the first order in IMAGE. Getting this right is unimportant, since you have to option of setting the order numbers explicitly during ECHSELECT.

MDELTA

This is the increment to the order number as the orders listed in the coefficient file are processed. Conventionally, if the first order is that with the lowest Y value, the increment will be -1. Note that the order in which the orders appear in the collapsed echellogram depends on the sign of MDELTA.

OBJOUT

Once the cross-sections for each order are selected, ECHSELECT sums those for each order to produce the collapsed echellograms. Those selected for the object go into one, whose name is given by OBJOUT, and those for the sky into another. The object cross-sections for each order are simply summed into one cross-section of OBJOUT. The order in which the orders appear in the collapsed echellograms depends on MDELTA - if MDELTA is -1, higher orders are at lower cross-section numbers.

SKYOUT

Once the cross-sections for each order are selected, ECHSELECT sums those for each order to produce the collapsed echellograms. Those selected for the object go into one, those for the sky into another whose name is given by SKYOUT. The sky cross-sections for each order are summed into one cross-section of SKYOUT, but are scaled to match the number of object cross-sections for the same order. This should allow the two collapsed echellograms to be directly subtracted.

DISNCHAN

Length of displayed section.

MOVETOX

New plot centre x value.

ORDER

Next echelle order to work on.

LOW

Minimum value to display.

HIGH

Maximum value to display.

ADD

Used to confirm that more than one cross section are to be used for an order's object.

CLEAR

Used to confirm that all settings for an order to be cleared.

QUITSEL

Used to confirm quitting work on an echelle order.

Source comments:

 E C H S E L E C T

 Routine name:
    ECHSELECT

 Function:
    Interactive object and sky selection from echellogram.

 Description:
    This application takes a corrected echellogram (one that has had
    the orders straightened, probably by CDIST), and generates a
    number of collapsed echellograms (images where each cross-section
    is a separate echelle spectrum).  To determine which cross-sections
    should be added to produce the sky and object spectra it gets the
    user to indicate the relevant limits on a plot of the corrected
    echelogram collapsed in the spectra direction.  For each order
    the user can select a range of cross-sections to be used for the
    object, and a number of ranges of cross-sections to be used for
    the sky.  For each order, the object cross-sections are added
    and the sky cross-sections are added and then scaled by the
    factor (number of object cross-sections / number of sky cross
    sections).  The object cross-sections are formed into one collapsed
    echellogram and the sky cross-sections are formed into another
    collapsed echellogram.  Optionally, a straightened arc can also
    be processed using the same object and sky cross-section information,
    in this case producing two collapsed arc echellograms, one for the
    cross-sections designated as object, one for those designated as
    sky, but in this case without any scaling being applied.

 Command parameters:
    IMAGE       (File) The name of the corrected echellogram.
    XSTART      (Numeric) The first x-value to be used when collapsing
                the image along the wavelength direction.
    XEND        (Numeric) The last x-value to be used when collapsing
                the image along the wavelength direction.
    MSTART      (Integer) The order number for the first order.
    MDELTA      (Integer) 1 if order numbers increase with cross-
                section, -1 if they decrease.
    OBJOUT      (File) The name of the object collapsed echellogram.
    SKYOUT      (File) The name of the sky collapsed echellogram.
    DISNCHAN    (Integer) Length of displayed section.
    MOVETOX     (Numeric) New plot centre x value.
    ORDER       (Integer) Next echelle order to work on.
    LOW         (Numeric) Minimum value to display.
    HIGH        (Numeric) Maximum value to display.

 Command keywords:
    WHOLE       Yes if all of spectral range is to be used
    PREVIOUS    Yes if previous selection is to be used as a starting
                point for the interactive selection.
    ADD         Used to confirm that more than one cross section are
                to be used for an order's object.
    CLEAR       Used to confirm that all settings for an order to be
                cleared.
    QUITSEL     Used to confirm quitting work on an echelle order.

 Data quality information:  Ignored.

 Error data: Ignored.

 Authors: Keith Shortridge, AAO

 Files:
    Selections made by ECHSELECT are written to ECHSELECT.LIS in the
    default directory.  This begins with a number of comment lines -
    all of which have an '*' in the first column, and is then followed
    by a single line for each cross-section which has been selected,
    giving cross-section number and order number, in format 2I10.
    If the cross-section is part of the sky selected for that order,
    the order number given is the negative of the actual order number.
    (Note that this program cannot cope with zeroth order!).  This
    file is also that read if PREVIOUS is set.