EXTRAIT DU MANUEL DE REFERENCE...
ADD [NAME]
Adds the current image in memory and the image [name]. The result is in memory.
Image compositing is one of the applications of the ADD command. Compositing several images is, to a first approximation, like adding the exposure times of each of the images.
See also: ADD2, COMPOSIT, DRIZZLE
ADD2 [NAME] [NUMBER]
Adds [number] images in the sequence of images having the generic name [name].
Example :
ADD2 I 3
adds the images I1.PIC, I2.PIC & I3.PIC.
ADD3 [NAME] [FWHM] [NUMBER]
When using the command REGISTER with deep-sky images, a file FWHM.LST is created on your hard drive. In this file,
the first column contains an image index and the second one corresponds to the largest FWHM (along either X or
Y axis, whichever is greater) of stars within the image.
Images indexes appears according to increasing FWHMs. So, it is possible to determine the best images in the series
by a simple look at this file. The command ADD3 is essentially the same as ADD2, except that only the images with
FWHM better that [FWHM] will be added. ADD3 uses the file FWHM to do so. Then you may add only the best images
of the series.
Example:
ADD3 M51- 1.9 12
ADDNOISE [SIGMA] [e-/ADU]
Adds noise to an image. The noise is characteristic of a CCD image where:
[sigma] = the standard deviation of the detector noise in Analog Digital Units (ADU)
[e-/ADU] = the gain in the acquisition chain in electrons/ADU
In this formula, the detector readout noise is quadratically added to the signal noise (photon noise).
Example:
ADDNOISE 1.5 30
Adds noise to the image in memory. The detector has the following (typical) characteristics: readout noise: 1.5
ADU, gain: 30 e-/ADU.
This command is useful for synthesizing realistic artificial images (testing deconvolution functions, for example).
AF3 [COEF]
Adaptive filtering of the noise in an image. Adaptive filtering consists of adjusting the strength of the filter
as a function of local statistical criteria. The filter will be most active where the signal to noise ratio is
low. This type of filter reduces the noise while conserving a maximum of details in the image.
The parameter [coef] contains a value that fixes the global strength of the filter. The filter does not act if
[coef]=0, and the filter gets stronger as the value of [coef] increases. Typically, [coef] is between 0.1 and 5.
AF3 uses a zone of 3x3 pixels, centered on the pixel being processed, for the statistical calculation.
See also: AF5, MMSE
The AF3 command is a remarkably effective tool for reducing the noise in an image while preserving a maximum of
details. This command (or AF5) is often chosen for this type of application instead of the filters whose action
is isotropic (like those provided in the GAUSS command).
AF5 [COEF]
Same command as AF3 with a 5x5 array.
ALL
Displays the current image on the whole screen. Press the <ESC> key to return to normal mode.
ANG_FILTER [XC] [YC] [RADIUS] [SIZE]
Performs a low-pass filter on rings centered to ([xc],[yc]). The algorithm computes the average of pixels in the
ring in sectors of [size] degrees.
The command uses a rectangular to polar transformation, so [xc], [yc] and [radius] have the same as in the REC2POL
and POL2REC commands.
The ANG_FILTER command is generally use to enhance radially structured features in images, such comet or a solar
jets visible during a total solar eclipse. The following example uses an image obtained during an eclipse observed
in the Guadeloupe Island on March 26, 1998.
First, we get a non-filtered image by using the command with a 0 value for the [size] parameter:
LOAD ECLIPSE ANG_FILTER 330 259 250 0 SAVE I
Then we create a filtered image:
LOAD ECLIPSE ANG_FILTER 330 259 250 5 SAVE J
And then, we perform the unsharp masking:
LOAD I SUB J 1000 VISU 1300 800
ANIMATE [NAME] [DELAY] [NUMBER]
The ANIMATE command displays, in sequence and cyclically, a series of images. This creates the effect of watching
a movie. The parameter [name] contains the generic name of the sequence images. The first index must be 1. The
parameter [number] contains the number of images used for the animation. The maximum number of images is 36. The
[delay] parameter is the time between two images, in milliseconds.
Example:
ANIMATE MARS 50 20
Animates the sequence MARS1.PIC...MARS20.PIC with a 50ms delay between each couple of images.
In astronomy, there are many objects that have significant temporal changes. A dynamical and accelerated analysis
of these changes often provides original astrophysical results. We can, for example, mention the study of granulation
and sun spots (the powerful cartographic capabilities of QMiPS32 compensate for the perspective effect due to the
sun's rotation and improve the appearance of the animation), the study of the rotation of cometary nuclei, or of
planetary meteorology.
In its simplest form, animation can be performed with only two images. This allows you to easily detect any difference
between the two images: a particular detail that is present in only one of the images can be revealed by the blinking
effect. This is an alternative to the BLINK command. Contrary to that command, ANIMATE does not allow the relative
displacement of the two images at the same time that they are compared. It is first necessary to superimpose them
with commands like TRANS, REGISTER, etc.
APHOT [FWHM] [SIGMA] [SATURATION]
Performs the automatic photometry of the image in memory. The method consists in identifying the most typical stars
of the field, i.e. bright but not saturated, isolated, and with a uniform sky background.
A reference star is computed by adding all these stars that were carefully registered. Then the photometry consists
in fitting the reference star to all the stars within the field and to subtract them. An ASCII file called STAR.LST
is created by the command: it contains the coordinates of each star and their instrumental magnitude (relative
to the reference star).
The [fwhm] parameter has to be given the value of the star FWHM (see e.g. PSF or MOFFAT). Generally, [fwhm] ranges
between 1.5 & 3.
[sigma] is the level with respect to the noise in the sky background. A good choice is about [sigma]=5. [saturation]
is the estimated level of saturation in the image (in coding steps). Use the cursor to measure the maximum level
of the brightest stars.
The result of APHOT is an image where all detected stars are removed.
See also: APHOT2, APHOT3, PHOT, PHOTM, FILE_PHOT, FIND_STAR.
Example:
LOAD GRAGG1 APHOT 2.5 5 32600
The double circles identify reference stars. When a star is measured and removed, a small cross appears at its
position.
APHOT2 [FWHM] [SIGMA] [SATURATION] [MODE]
Same command as APHOT but here the stars are simulated by a mathematical function called Moffat function. Moreover
APHOT2 takes into account the residuals of the estimation with respect to the mathematical model. The first parameters
are the same as for APHOT.
The [mode] parameter may vary between 1 and 4. Its value determines a performance level for the algorithm, in order
to measure faint or close stars. if [mode]=4, several iterations are made so that the brightest stars are removed
in the beginning order to detect the faintest ones. Note that the running time of APHOT2 is longer than the one
of APHOT.
Example:
LOAD GRAGG1 APHOT2 9 5 32600 2 SAVE I LOAD GRAGG1 SUB I 300
The last image contains all the detected stars.