.. C-Munipack - User's manual
Copyright 2012 David Motl
Permission is granted to copy, distribute and/or modify this document under the
terms of the GNU Free Documentation License, Version 1.2 or any later version published
by the Free Software Foundation; with no Invariant Sections, no Front-Cover Texts, and
no Back-Cover Texts.
$Id: project_settings_dialog.rst,v 1.3 2012/11/17 08:31:55 dmotl Exp $
.. index::
pair: Project settings; dialog
.. _project-settings-dialog:
Project settings (dialog)
=========================
The "Project settings" dialog is used to set up the parameters of
the data processing and output. User interface options that do not affect
the data processing are places in the separate dialog "Environment options".
Among many parameters of the aperture photometry procedure a special attention
should be payed to the following: Filter width and the Detection threshold. These parameters
control mainly the detection of stars on the CCD frames. By decreasing the Filter width value
the fainter stars will be found. It is to be pointed out, that too small value may take the
artefacts on the background as regular stars. The Detection threshold value sets the distance
between the finest stars detected and the background sky noise. The value is entered in
multiplies of background standard deviations.
Activating the dialog
---------------------
The dialog can be activated:
.. |preferences_icon| image:: ../../share/icons/preferences.png
#. from the main menu: :menuselection:`Project --> Edit properties`.
#. from the main toolbar: |preferences_icon|
The dialog controls
-------------------
.. figure:: images/editproject_couts.png
:align: center
:alt: Project options dialog
The "Project options" dialog
\(1) Select a category.
Parameters in the selected category are shown on the right pane (2).
Click "Set defaults" button (3) to set the parameters in the selected
category to the default values.
Click the button (4) to save the settings as current configuration.
Configuration profiles
----------------------
If you process the data from multiple cameras or telescopes,
you will need to adjust the project options for each setup. The program
allows to store the configuration to a file and then load it back.
To save the current settings to a file, click on the "Save to profile"
button. A standard save dialog appears. Enter a name of the file, you can
also change the target direcory. Confirm the dialog.
To restore the settings from a file, click on the "Load from profile"
button. A standard open dialog appears. Look up the file with saved project
options and confirm the dialog. Please note, that your current project
settings will be overwritten by this action.
Camera
------
Camera parameters
- Read noise - readout noise in electrons, you should enter the proper value stated
in the camera's documentation. Default: 15.0
- Gain - number of electrons per ADU, you should enter the proper value stated in
the camera's documentation. Default: 2.3
Source frames
-------------
Source frame conversion and processing parameters
- Min. pixel value - lowest value of pixel in ADU. All pixels, which are equal to
or less than specified value are considered to be invalid, by default: 0
- Max. pixel value - highest value of pixel in ADU. All pixels, which are equal to
or greater than specified value are considered to be overxposed, by default: 65535.
- Image data format - pixel data format in which the working files are
stored. If the "Autodetection" is selected, the program keeps the format of
original source files. Otherwise, the data are transformed during the Fetch/Convert
operation. Default: Autodetection
- Binning - reduction of frame size. When this feature is enabled, the
program will sum the pixel values from groups of neighboring pixels making
one pixel for each group in the working frame. This transformation is performed
in the Fetch/Convert operation. This is useful for processing images from the
hi-resolution DSLR and CCD cameras. Please note, that the sum of pixel values
are computed (not average), so you when you enable binning, you will probably
need to increase the "Max. pixel value". Default: No binning
- Border - skip invalid parts of the source frames. Set up frame borders
to nonzero if you need to remove parts of the frames from the processing. Default: 0
Calibration
-----------
Parameters for bias, dark and flat corrections.
- Standard calibration - in the standard calibration scheme, only
two correction frames are used - a dark frame, which also includes the bias,
and a flat frame. The standard calibration scheme is simpler to follow,
but it requires that the dark frame must be of the same exposure duration
as source frames.
- Advanced calibration - in the advanced calibration scheme, all three
correction frames are applied separately - a bias frame, a dark frame
and a flat frame, in that order. The dark frame must not contain a bias,
such dark frame is called scalable dark frame, because it need not to be
of the same exposure duration as source frames.
Star detection
--------------
Parameters for detection of objects on a frame. This step is done
during the Photometry operation.
- Filter width (FWHM) - full width at half maximum of the Gaussian filter.
The low-pass filter is applied to the source image before searching for
local maxima. If profile of objects on frames roughly corresponds to the
Gaussian function, the good value for the filter width is the FWHM of
objects. You can use the Quick Photometry tool in the Preview window
to measure the FWHM of objects. In case the profile of objects is not
a Gaussian function and the program splits stars into two or more objects,
you need to raise this value. Default: 3.0
- Detection threshold - the level which a brightness enhancement must have above
the background level to be considered as a real object. The value is given
in standard deviations. The best starting point is the default value 4.0.
Process a set of frames and check the results. If you need to detect fainter
object, reduce it. If many background artefacts are considered as stars,
raise it. Run the photometry again and repeat the steps until the results
are satisfactory. Please note, that the filter width also affects the
detection capabilities. Default: 4.0
- Minimum and maximum sharpness - minimum and maximum value of sharpness
which a brightness enhancement must have to be considered a real object. The main
purpose is to eliminate bad pixels, it may also help to eliminate blurred objects
such as nebulaes and galaxies. Defaults: 0.2 and 1.0
- Minimum and maximum roundness - minimum and maximum value of roundness
which a brightness enhancement must have to be considered a real object. This test
is intended to eliminate bad rows and columns, it may also help to eliminate
galaxies or cosmic particle traces. Defaults: -1.0 and 1.0
Photometry
----------
Parameters for aperture photometry.
- Aperture - the program computes brightness of stars in all defined
apertures. It is possible to define at most 12 apertures. An user can
select one of them when making output data, a light curve for example.
The aperture is defined by its radius in pixels.
- Inner and outer radius - local background level is measured in
an annulus that is centered on the object. These parameters define
its inner and outer radius in pixels. Defaults: 20.0 and 30.0.
Matching
--------
Parameters for matching stars.
- Standard algorithm - identifies similar polygons of stars and
find the best match. It works well if a source frame is scaled, rotated
or even mirrored with respect to the reference frame. The limitation is
that it requires at least three stars on a frame.
- Algorithm for sparse fields - this algorithm can match frames which
contain at least one star. Scale, tilt and position of a source frame
with respect to the reference frame should be close. Otherwise, it
leads to a false match.
Standard algorithm parameters
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
- Read stars - if a source or reference file contain more than
given number of stars, the program reads only that number of
brightest stars. This limit speeds up the computation. Default: 10
- Identification stars - a number of stars that are identified
in each iteration. More information is given in the theory of operation.
Default: 5
- Clipping factor - tolerance used during the iterative evaluation
of the transformation coefficients. Default: 2.5
Parameters of sparse-fields algorithm
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
- Max. offset - maximum offset between a source frame and a reference
frame in pixels. It is intended to eliminate false matches. This parameter
should as high as the highest offset of an object of frames, but no higher.
Default: 2.0
Light curve
-----------
Parameters for making a light curve.
- Allow using an artificial comparison star - this extension allows
an analyst to select more than one comparison star. By averaging their
brightness, the program computes brightness of a artificial star and
use it intead of a normal comparison star. This reduces a noise of a
measurement. Default: unchecked
Master bias
-----------
Parameters for making a master bias frame.
- Output data format - pixel data format in which the master bias frame is
stored. If the "Autodetection" is selected, the program keeps the format of
working files. Otherwise, the data are transformed into specified format.
Default: Autodetection
Master dark
-----------
Parameters for making a master dark frame.
- Make scalable dark frame - make a master dark frame that can be
scaled to match the exposure duration of a source frame and a dark
correction frame (see the advanced calibration scheme for further
information). When you check this option, you have to subtract
a bias frame from your dark frames before you make a master dark frame.
- Output data format - pixel data format in which the master dark frame is
stored. If the "Autodetection" is selected, the program keeps the format of
working files. Otherwise, the data are transformed into specified format.
Default: Autodetection
Master flat
-----------
Parameters for making a master flat frame.
- Output data format - pixel data format in which the master dark frame is
stored. If the "Autodetection" is selected, the program keeps the format of
working files. Otherwise, the data are transformed into specified format.
Default: Autodetection
- Output mean level - the program normalizes the master flat frame so
its mean level is equal to a given value. If it is set too high, the output
frame has many overexposed pixels. On the other hand, too low value raises
the noise when a integer pixel format is used, because pixel values in a frame
are rounded to the nearest integer values. Default: 10000
Merge frames
------------
Parameters for frame merging.
- Output data format - pixel data format in which the merged frame is
stored. If the "Autodetection" is selected, the program keeps the format of
working files. Otherwise, the data are transformed into specified format.
Default: Autodetection
Find variables
--------------
Parameters for finding new variables.
- Clipping threshold - minimum share of valid brightness measurements
that a star must have to be included in the mag-dev graph. This test
is intended to eliminate stars that have few valid measurements only
and their position in the mag-dev graph more or less random. Default: 60
Observer
--------
Observer's geographic coordinates.
- Name - any text identifying the observing location, i.e. name of the town
- Longitude - observer's longitude in degrees. Use the hexagesimal format, separate
the fields by a space character. Enter 'E' character at the first position in a string to indicate
that the location is on the eastern hemisphere or 'W' character for locations on a western hemisphere.
- Latitude - observer's latitude in degrees. Use the hexagesimal format, separate
the fields by a space character. Enter 'N' character at the first position in s string to indicate
that the location is on the north hemisphere or 'S' character for locations on a southern hemisphere.
.. seealso:: :ref:`projects`, :ref:`profiles`, :ref:`environment-options-dialog`
