There are presented examples of runs of Munipack by using of the command line interface. The tasks can be also done by more intuitive way with the graphical interface. The first example shows a long time photometry set and the second one is dedicated to a deep sky object.
A sample data for both runs are available as munitut-blazar.tar.gz and munitut-bubble.tar.gz. Use command tar zxf munitut-blazar.tar.gz and tar zxf munitut-blazar.tar.gz to unpack it to a current directory. We will assume that the sample data are unpacked to /tmp directory as /tmp/munitut-blazar and /tmp/munitut-bubble.
bash$ cd /tmp/ bash$ tar zxf munitut-blazar.tar.gz bash$ tar zxf munitut-bubble.tar.gz
We have a set of images, flat-fields and dark-frames for the images. Our goal is to get a light curve (a time dependence of magnitude) of the blazar. The same approach can be used for any object as a variable star, an exoplanet, etc.
| Description | Filemask | Exposure |
|---|---|---|
| scientific images | 0716_[1-9]R.fits | 120 sec |
| dark-frames of scientific images | d120_[1-7].fits | 120 sec |
| flat-fields | f10_[1-9]R.fits | 10 sec |
| dark-frames of flat-fields | d10_[1-9].fits | 10 sec |
As a first important step, we will create a working directory. For example, create /tmp/munitut by the command:
bash$ mkdir /tmp/munitut bash$ cd /tmp/munitut
The name of the directory is arbitrary. It is highly recommended to use any empty directory to prevent unwanted replacement of any data (especially of original images!).
We will create a mean-dark for scientific exposures. Run the command:
bash$ munipack mdark -r -o d120.fits /tmp/munitut-blazar/d120_*.fits
Munipack is invoking the module mdark intended to average (by mean) of specified images as the last argument. The asterisk marks all images begins with d120_ together with a suffix .fits. The -r sets to use of robust method of estimation of mean and the output mean itself is stored as d120.fits.
The parameter -r is optional, but highly recommended. It reduces of fluency of cosmic-rays and one-image defects. On the other side, it requires more computer resources.
In principle, this step can be omitted, but it is a good practice from a statistical point of view. The output image is frequently called as the master-dark.
A randomly selected dark image.
Mean of dark-frames (master-dark).
Original scientific images can be corrected for dark-frames by running:
bash$ munipack dark -x . d120.fits /tmp/munitut-blazar/0716_*R.fits
dark options subtracts, the previously created mean-dark d120.fits given as a first non-optional argument, from every scientific exposures of 0716+71 and produced new images will be stored in the current working directory with image names identical to original ones when the option -x . (note the dot) is used.
A randomly selected scientific exposure of blazar 0716+714.
A randomly selected scientific exposure of blazar 0716+714 with the d120 dark-frame subtracted.
There is a triple step procedure for creating of the running mean of flats
bash$ munipack mdark -r -o d10.fits /tmp/munitut-blazar/d10_*.fits bash$ munipack dark -x . d10.fits /tmp/munitut-blazar/f10_*R.fits bash$ munipack aflat -o autoflat.fits f10_*R.fits
The first two lines are a modification of our previously described examples (The original flat-field images are corrected about their mean-dark and stored in the current directory.) Let's look on last line. The corrected flat-fields are scaled by its mean intensity and its dispersion to a unified output level. A robust mean is made on the uniform scaled flats and an output flat is stored as autoflat.fits. The output image is frequently called as the master-flat.
The key feature of aflat is the scaling and a robust mean of single flats. The procedure is pretty effective for short series of the twilight sky's exposures when brightness rapidly decrease. Also, a long over-night series of non-identical fields (like many blazar fields) will produce excellent results.
A randomly selected flat-field image.
A scaled robust mean of flat-fields (master-flat).
By analogy of dark correction, scientific images (subtracted for dark) can be corrected for flats by
bash$ munipack flat -x '!' autoflat.fits 0716_*R.fits
We can see that the current directory images are used. With parameter -x '!' (note apostrophes) the input images will be replaced. It may be potentially dangerous!
A randomly selected, fully corrected (dark and flat), image of blazar 0716+714.
… Other routines will be added soon. Please, continue on Tutorial of Classics edition. …
Copyright © 1997-2011, F. Hroch (✉, Blog⤴), DTFA, Masaryk University.