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VaST [Variability Search Toolkit]A software for variable star detection
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VaST is a software tool for finding variable objects on a series of astronomical images. The images (CCD frames or digitized photographic plates) must be taken with the same instrument using the same filter and saved in the FITS format. CCD images should be calibrated (dark-subtracted and flat-fielded). The input images may be shifted and rotated with respect to each other, but they have to have the same scale (arcsec/pix). The images in a series should overlap by at least ~40% to ensure successful cross-identification. VaST performs object detection and aperture photometry using SExtractor on each image, cross-matches lists of detected stars, performs magnitude calibration with respect to the first (reference) image and constructs a lightcurve for each object. The sigma-magnitude, Stetson's L variability index, Robust Median Statistic (RoMS) and other plots may be used to visually identify variable star candidates. If data permit, period-search techniques may be employed to identify periodic variable stars among the candidates. All lightcurves are constructed in arbitrary magnitudes with zero magnitude corresponding to the background level on the reference image. If there are reference stars with known magnitudes in the field of view, all magnitudes can be later converted to the standard system. Unlike software based on the image subtraction method, VaST can be used in case of unstable PSF (e.g., bad guiding or with digitized wide-field photographic images). VaST is not tied up to any external catalog and WCS (if operated in its main "variable star search" mode), so it can be used on images taken with a telephoto lens as well as with a 2.6-m class telescope. If needed, absolute astrometric calibration may be performed through an interface to the Astrometry.net code allowing one to perform automatic magnitude scale calibration and variable star identification (however, this will work only if the input images are large enough to perform blind plate solution). VaST is written in C (and partly in BASH scripting language) for GNU/Linux operating system. The latest versions are also tested on MacOS X and FreeBSD. The best practical way to run VaST under Windows is through Linux installed in a virtual machine (e.g. VirtualBox, see also a collection of pre-built VirtualBox images). The AAVSO forum thread mentions attempts to run VaST under Windows with Cygwin, but the results seem to be inconclusive. On all the supported systems VaST is able to utilize multiple processing cores to perform most of its computations in parallel. VaST is free software: you can redistribute and/or modify it under the terms of the GNU General Public License. The program is in a continual, albeit slow, state of development. You are welcome to contribute bug reports, patches and feature requests: please write me at kirx[at]scan.sai.msu.ru ScreenshotsVarious VaST subroutines (lightcurve plotter, image viewer) may be started automatically from the main program or manually by a user from a terminal. Names of the corresponding executable files are given under each screenshot. Click on images to see them in high resolution:
Video (screencast) voice comments are in Russian only, sorry... I hope to prepare an English version for quite a few years already...
Getting VaSTTo compile and use VaST you'll need:
You can find at this page the latest version of VaST (download via ftp or http, ~9.5M) along with the sample data set (ftp or http, 24M). Files described here as well as older versions of VaST are available via our anonymous FTP.You may download VaST with the command wget -c ftp://scan.sai.msu.ru/pub/software/vast/vast-latest.tar.bz2
unpack the archive containing the program
tar -xvjf vast-latest.tar.bz2
and compile it by running
cd vast-1.0rc75
make
(or 'gmake' if you are not on Linux).
At this point VaST should be ready for work.
If compilation fails, read the output carefully. Most probably it can't find some necessary libraries, header files or external programs. Please install the required programs and try to compile VaST again. If you are sure that the needed libraries and headers are installed in the system but the compiler cannot find them, try to open Makefile with a text editor and change the libraries locations to match your environment. Very old versions of VaST require PGPLOT, CFITSIO and GSL libraries to be installed in your system, but most likely you don't want to use such an old VaST version. Special note for Ubuntu users! The following installation procedure is recommended:
Special note for FreeBSD users: VaST scripts may fail to compile the internal copy of PGPLOT library. If that happens, please install PGPLOT system-wide with the command (as root): pkg install pgplot
then try to compile VaST again.
Please use gmake instead of make to compile VaST.
Using VaSTTo try VaST, download the sample data set, unpack it
wget -c ftp://scan.sai.msu.ru/pub/vast/sample_data.tar.bz2
change to the VaST installation directory and run the program
tar -xvjf sample_data.tar.bz2
cd vast-1.0rc75
After a brief computation the variability search window will be opened. Click
on any star on the sigma-magnitude plot to inspect its lightcurve. Click on
any point on the lightcurve plot to see an image from which this point
comes. The star on the image will be marked with a red cross, a red circle
around the star corresponds to the aperture used to measure this image.
You may switch from sigma to other variability indexes by pressing 'M' or 'N'
on the keyboard in the sigma-magnitude plot window.
./vast ../sample_data/*fit If you quit the program without deleting any data, you can restart it without doing all the computations again by running:
./find_candidates aa
To calibrate the magnitude scale using comparison stars with known magnitudes within the field of view use this script:
util/magnitude_calibration.sh
It will ask you to specify one or more comparison stars and their magnitudes.
For each comparison star, click on this star on the displayed image then
enter its catalog magnitude in the terminal window.
After the comparison stars have been specified, close the image window with the right mouse click and inspect the relation between instrumental and catalog magnitudes. This relation may be fitted by a linear function with the slope fixed to 1, linear function with a free slope, second degree polynome (parabola) or the Bacher et al. (2005, MNRAS, 362, 542) magnitude calibration relation a.k.a "photocurve". This option is suitable for processing digitized photographic plates. Use (P) key on your keyboard to change the fitting function. For most CCD data sets, linear function with the fixed slope provides a good fit. The data points may be weighted according to their estimated errors or weighted equally. Use (W) key to change weighting. Close the dialog with the right mouse click to apply the calibration to all stars when you are satisfied with the fit. If the image field of view is large enough to be blindly solved with Astrometry.net code (as described below), one can automatically match stars detected on the image to the UCAC4/APASS catalog by running the magnitude calibration script with a command line argument specifying the observing band:
util/magnitude_calibration.sh V
The acceptable bands are:
"C" - UCAC4 unfiltered red band,
"B" - APASS B band,
"V" - APASS V band,
"R" - APASS R band,
"r" - APASS r band,
"i" - APASS i band. Magnitude calibration against APASS can be performed
only if the field of view overlaps with the APASS survey footprint.
Note that the automated magnitude calibration will not work with the
sample data set due to its small field of view.
In order to save the current work, use the script
util/save.sh my_favorite_field_name
If the field name was not provided, the script will ask for it. To restore previous
work, use
util/load.sh my_favorite_field_name
or just copy all saved files from directory [my_favorite_field_name] back to the VaST directory.To delete all files from the previous work, you can use:
util/clean_data
There is a tool to automatically identify variable stars detected with VaST. It requires a working Internet connection at runtime. The tool may or may not work for your field depending on luck. If the field of view is greater than, say, 30' and the image quality is fine - the odds that the automatic plate solution will work for your field are pretty good. Here is how to use it... To identify the star number 00190 in the current dataset use the following command:
util/identify.sh out00190.dat 25
where "out00190.dat" is the lightcurve file of the star and "25" is the
estimated field of view size in arcminutes. It is wise to set this value a little bit smaller
than your best-guess field of view. If no field of value is given, the
default value of 40' will be assumed. Note, that the field of view
identification may take really long time (up to ~30 minutes), especially for small
fields. Please, do not interrupt the process - just wait for a result. If
the field identification failed, try to restart it with smaller estimated
field of view size. On successful identification, the script will print the
equatorial coordinates (J2000) of the star and will attempt to query popular
databases to check if this star is already known as a variable. Note, that
the coordinates returned by the identification script may be up to 10" off.
We strongly advise to use the Aladin
interactive sky atlas to verify the identification and obtain more
precise star coordinates from some astrometric catalog (e.g., USNO-B1.0).
The automatic identification function relies on tools provided by Astrometry.net. For more details visit
http://astrometry.net/. Note, that
according to the
use conditions of the index files required to run the Astrometry.net
code, you need to be ready to share the images solved using this software
with any other interested party including the Astrometry.net team. According
to the same use
conditions: "If the indexes are used in any scholarly work,
research grant proposals or other scientific or academic
publications, the Astrometry.net project must be properly cited
and acknowledged. The paper to cite is the Lang et al paper on our
bibliography page http://astrometry.net/biblio.html.
The acknowledgment text is "This research made use of tools provided
by Astrometry.net." The VaST software developers assume, that this statement
concerns the work which uses "util/identify.sh" script from the VaST
package.
A note on the graphical user interfaceThe VaST GUI is based on the PGPLOT library. The main reasons are that this library is perfectly suited for displaying and editing data and image plots and is so easy to use from programmer's standpoint. The problem is that the resulting interface may look counterintuitive. The unusual thing about the VaST interface is that it has no buttons. (There is a way to program a GUI with buttons and graphical input fields in PGPLOT, but, trust me, you'll not be impressed by its look and usability.) So, whenever a user has a choice between multiple possible actions, instead of clicking a button to execute the desired action, a user will have to physically press a key on a keyboard. The list of possible keys is always displayed by VaST at the terminal. Please have a look there to know your options. Some actions are common to all VaST windows:
Using VaST with scanned photographic platesIf you have to deal with digitized photographic materials, you'll want first to convert TIFF images (which are typically produced by scanner software) to the FITS format. It can be easily done with the tiff2fits converter. Do not forget to change your images to positive (white stars on black sky). For example:
./tiff2fits -i input.tiff output.fits
Also, you'll have to enter the information about the date and time of the
observation in fits header. This can be done, among other ways, using the
modhead program from the CFITSIO
examples page, MissFITS or edhead from the WCSTools package. You may
enter the observation date and time information in the image header by generating
the usual "DATE-OBS" and "EXPTIME" header keys, or by simply putting the
middle-of-exposure Julian Date into the "JD" key.
You will most likely need to modify the default SExtractor settings stored
in the "default.sex" file located in the VaST directory. Please use
"default.sex.beta_Cas_photoplates" and "default.sex.PHOTO" as working examples
(these files are also found in the VaST directory).
Say, you have digitized photographic images in "photo_data" directory. To run VaST on them, change to the VaST directory and run the program
cd vast-1.0rc75
The "-o" parameter tells VaST to use formulas (1) and (3) from
Bacher et al. (2005, MNRAS, 362,
542) a.k.a. "photocurve" for magnitude calibration. This technique provide slightly better
results for the aperture photometry on photographic data compared to the
second-order polynome used in VaST by default for magnitude calibration.
However, the standard calibration technique should also provide reasonably
good results (see Figure 2 in this paper).
The "-j" parameter that forces VaST to use a linear position-dependent
magnitude correction (i.e. stars on one side of the image bing
systematically fainter than on the other side) might also be useful for
photographic plates photometry.
./vast -o ../photo_data/*fit An example photographic dataset is available here. Beware, it's about 1G in size! You may find some more details in the ArXiv:1403.5334 e-print "A search for new variable stars using digitized Moscow collection plates". Search for transients with VaSTApart from the standard "variable star search mode", where a long series of images is processed and lightcurves of detected stars are explored using the sigma-magnitude plot, VaST can be also used in the specialized "transient detection mode". In this mode VaST will process a series of four images: two first-epoch (reference) images and two second-epoch images. VaST will generate an HTML report containing a list of candidate transients. The transients are defined as either objects that were not visible on the reference images, or where at least 1 mag. fainter compared to the second-epoch images. Two first-epoch images are needed because image artifacts and star blending may cause VaST to miss a star on a single reference image, so it will appear as a false transient search mode is available. If there are two reference images - chances that the program will fail to detect a star at both of them is greatly reduced. Also note that two different reference images are needed: it would be impossible to "cheat" the program by feeding the same image to it twice. An example dataset that allows one to test the transient search mode is available here. The unpacked archive will contain two sub-directories with reference and second-epoch images. The search should be conducted in two steps:
# Process images with VaST
./vast -x99 -ukf ../transient_detection_test_Ceres/reference_images/* ../transient_detection_test_Ceres/second_epoch_images/*
# Run script that will generate an HTML report
util/transients/search_for_transients_single_field.sh
Be prepared - the script will ask you to download a few catalogs needed for its work, including Tycho-2, the catalogs are more about 200M in size. The transient search report will be placed in transient_report/index.html that should be opened with your
favorite web browser. The report will contain a few false candidates and some good ones including asteroids and variable stars.
Known limitations:
Some switches that you may use with VaST"-P" — perform PSF-fitting photometry with SExtractor and PSFEx."-9" — use DS9 instead of VaST's own viewer pgfv to view FITS files. "-u" — always assume UTC time system, don't perform conversion to TT. "-k" — force VaST to ignore the "JD" keyword in FITS headers. "-x2" — accept stars with non-zero SExtractor flag: 2 - blended stars, 4 - saturated stars, 99 - accept everything. "-e" — failsafe mode: only stars detected on the reference frame will be processed. "-p" — tell VaST that it deals with a linear detector. This flag is useful for well calibrated CCD images, but for some CCD images it is better not to use it. Test what works best for your particular dataset! "-o" — tell VaST that it deals with a digitized photographic plate. The magnitude calibration between frames will be done using the relation proposed by Bacher et al. (2005, MNRAS, 362, 542). "-l" — perform sigma-filtering of lightcurves. "-r" — assume that images are not rotated with respect to each other by more than 3 degrees. To get the full list of the available command line arguments run:
./vast -h
Description of output files produced by VaSTAfter processing an image series, VaST will create a number of files in its working directory that may be useful for a future work or problem debugging.
VaST mailing listIf you would like to receive updates about new versions of VaST, please enter your e-mail address in the form below or just drop a line to kirx[at]scan.sai.msu.ruRelease notes21 Feb 2016: version vast-1.0rc75: * Minor modifications to speed-up the star matching algorithm. * When manually opening a lightcurve file with './lc' it is now possible to refer to the star only by its number without specifying the full filename, i.e. './lc 12184' instead of './lc out12184.dat'. The old way with the full file name still works, of course. * VaST can now properly handle the situation when DATE-OBS keyword is present in the FITS image header, but does not specify the observing time and a separate TIME-OBS keyword is not present. In this case, VaST will try to get the observing date from JD keyword. * Rewritten the SysRem algorithm implementation (Tamuz, Mazeh, Zucker, 2005, MNRAS, 356, 1466). The new version should work faster and be less aggressive in rejecting uncorrectable stars. The new implementation may be run as util/sysrem2 I'm keeping the old util/sysrem too for now. * Changed the way maximum trial period is set for the period search in pokaz_laflerkinman.sh Now pmax=int(jd_range/3.0-0.5) * Fixed the experimental script that retrieves Catalina sky survey data for a specified (small) sky area: util/catalina_search_area_TEST.sh * Added the interquartile range (IQR) as another measure of lightcurve scatter. In practice it turns out to be very similar to the median absolute deviation (MAD) that was added earlier. * Added a small tool that splits multi-extension FITS files into single-extension FITS images that can be processed with VaST: util/split_multiextension_fits /path/to/my_multiextension.fits * Changed PSF extraction settings in default.psfex The new settings are more appropriate for a wide-field instrument. The old settings may be found in default.psfex.small_FoV It may be a good idea to apply a few iterations of SysRem ( util/sysrem2 ) to remove residual systematic effects arising from imperfect PSF reconstruction that may degrade photometric accuracy for bright stars. * Changes in util/solve_plate_with_UCAC4 to make it work faster. The results of its work are not exactly the same as in the previous version, but should be still acceptable. * Circumvent the mysterious gcc bug that refused to compile VaST with the parameter "-march=native" set on some combination of gcc version and CPU model. The new test is trying to compile the problematic C-source file and does not set "-march=native" if this test compilation fails. * Minor improvements in the Makefile to speed-up compilation. The changes also allowed to fix problem with compilation on some Ubuntu systems. Unfortunately, the changes rely on GNU make syntax, so if you are on non-Linux system, it is now necessary to compile VaST with 'gmake' instead of just 'make'. * Fixed the VaST testing script ( util/examples/test_vast.sh ) that reported a failed test after the variable "NSV 11188" got its GCVS name "V1451 Her" that was not previously recognized by the script. * Increased timeout for plate-solving (both remote and using a local copy of Astrometry.net software). 24 Oct 2015: version vast-1.0rc74 * VaST is now not trying to create a flag image in cases where there are many zero-value pixels scattered across the image rather than being grouped in specific areas (like along a frame edge). This makes it possible again to process background-subtracted images with VaST. * Fixed the bug with incorrect observing time being set from "EXPSTART" keyword. No problem appeared if other keywords ("DATE-OBS", "JD") were present in an image header. * By default, VaST now accepts stars having SExtractor flag set to 1: "The object has neighbors, bright and close enough to significantly bias the photometry, or bad pixels (more than 10% of the integrated area affected)." It appears that in practice many stars that can be measured well get this flag. As always, you may manually specify the maximum acceptable SExtractor flag with '-x' option on the command line: # Accept blended stars ./vast -x3 /path/to/my/images*.fit # Accept everything including saturated stars ./vast -x99 /path/to/my/images*.fit * VaST now compiles with link time optimization (LTO) enabled by default on Linux systems. If this doesn't work for you - remove `lib/set_lto.sh` from OPTFLAGS in Makefile and re--compile with 'make'. * Further improvements to the automatic testing script util/examples/test_vast.sh Beware, the script will download ~2Gb of test data and will need an hour to run! If you have fast internet connection, you are welcome to run this test script. Please write me if the test script reports any problems. * Added warning messages discouraging a user from running VaST on a small number of images (and then be disappointed by the result). Currently, the two 'proper' ways to run VaST are: 1) Run VaST on a long (50-100-1000) series of images and inspect lightcurves that show a large scatter. 2) Run VaST in the 'transient detection' mode on *four* (4) images: two reference and two second-epoch images. Then create an HTML search report by running util/transients/search_for_transients_single_field.sh VaST will run on a different number of images 2, 3, 5 (now printing the warning message), but the results are unpredictable. * Added Median Absolute Deviation (MAD) as one of the displayed variability indexes, see https://en.wikipedia.org/wiki/Median_absolute_deviation * Changed the "Modified sigma" index to the simple "Weighted sigma" * Stetson's J and L variability indexes computed using time-based weighting are now displayed. For a detailed discussion of these indexes see http://adsabs.harvard.edu/abs/1996PASP..108..851S and http://adsabs.harvard.edu/abs/2012AJ....143..140F * S_B variability detection statistic is now displayed, see http://adsabs.harvard.edu/abs/2013A&A...556A..20F for a detailed discussion. * The variability index plots are now displayed in the following order: 1) Standard deviation 2) Weighted standard deviation 3) Median Absolute deviation (MAD) 4) Robust median statistic (RoMS) 5) Stetson's J with time-based weighting of pairs 6) Stetson's L with time-based weighting of pairs 7) S_B variability detection statistic The first four indexes characterize the lightcurve scatter, Stetson's indexes (5 and 6) characterize the degree of correlation between consecutive measurements, S_B statistic (7) combines information about the correlation and the overall scatter. As before, you may switch between these plots by pressing 'M' or 'N' on the keyboard while in the variability search window (./find_candidates). * util/load.sh the script that loads work previously saved with util/save.sh now checks if SExtractor configuration files that are to be loaded are the same as the ones currently present in VaST directory. If the files are identical, the script doesn't bother user with the silly question "Do you want to rewrite a configuration file?". The program md5sum should be installed in your system for this functionality to work. * The VaST settings header file src/limits.h is renamed to src/vast_limits.h to avoid confusion with the standard C library header file also called limits.h * Edited src/gsl/Makefile.in so GSL can compile without makeinfo (texinfo) installed in the system. * Added timeout of 300 seconds to all network communications so the program doesn't hang indefinitely if the connection fails at a critical moment. * Changed the way all VaST subroutines read lightcurve files - now they use a dedicated function rather than simple 'scanf()'. This will eventually allow VaST to natively handle lightcurve files in formats other than the strict VaST format of "JD mag err X Y ap imagefilename". The downside of this change is that lightcurve reading is noticeably slower than it used to be. The support of multiple lightcurve formats is still in the experimental stage though. For now, in order to import ASCII lightcurve files in the format "JD mag err" into VaST use the script util/convert/three_column_ascii2vast.sh which will convert them into the strict VaST format. 23 Jun 2015: vast-1.0rc73 * Fixed the bug that caused VaST to fail if it tries to guess a saturation limit of an image that does not contain BUNIT key in its header (sadly, the majority of ground-based images do not have this keyword). * Saturated pixels with values = 65535 are not flagged-out in the flag image in order not to remove the saturated objects from the list of detections. The brightest objects, even saturated ones, are useful for image matching and performing a blind plate solution with the Astrometry.net code. * An additional aperture photometry run is performed for each image processed in the PSF-fitting mode. The goal is, again, to have the list of detections that includes the brightest stars. Under the normal circumstances, saturated stars are omitted by VaST from the list of detections when working in the PSF-photometry mode. The brightest stars are needed to perform blind plate solution with the Astrometry.net code. * VaST is not attempting to create a flag image for input images that contain many negative values as, in this case, zero-value pixels are likely not the bad ones and should not be flagged. * Restored the partly-broken transient detection mode. See the instructions at http://scan.sai.msu.ru/vast/#transientsearch if you want to try it. The links to external resources in the HTML transient search report located in transient_report/index.html (including MPChecker as well as CSS and NMW archives) are working again. * It is now possible to exit the catalog magnitude calibration plot by pressing 'x' on a keyboard. Before the program was expecting only the capital 'X' or right mouse click to exit. * Added timeout and retry attempts to util/solve_plate_with_UCAC4 subroutine in order to be able to recover from network connection failures during communication with VizieR. * Further improvements to the automatic testing script util/examples/test_vast.sh Beware, the script will download ~1.5Gb of test data! If you have fast internet connection, you are welcome to run this test script. Please write me if the test script reports any problems. * Updates and broken-link fixes on the VaST web page: http://scan.sai.msu.ru/vast/ * The outdated README file is replaces by an HTML page in doc/ directory. 10 Jun 2015: vast-1.0rc72 * Fixed the PSF photometry mode that was not working for images that do not require creation of an external flag image. * VaST is now trying to explicitly set GAIN value if it is found in the FITS header ("GAIN" keyword). You may also set the GAIN value manually in default.sex file - VaST will not try to override it if if it finds that the default gain value in default.sex is changed. VaST will also try to recognize "count" and "countrate" images where the image units are "electrons" and "electrons/s" instead of ADUs (electrons/gain) and set an appropriate gain value ("1" or equal to exposure time in seconds, respectively). The correct gain value is needed to estimate Poisson noise contribution to photometric measurement errors. See equation (61) in Section 10.4 of SExtractor documentation. Note that SExtractor itself will try to override both GAIN and SATUR_LEVEL values set in default.sex using FITS header keys specified in default.sex as GAIN_KEY and SATUR_KEY. Please set an appropriate gain value in default.sex if this information is not available from FITS image header. * The plotting programs ./find_candidates, ./lc, ./pgfv now ignore clicks outside the plotting area, so now one can easily switch between multiple windows by left-clicking green area outside the plot in each window. * The lightcurve viewer ./lc now marks the latest lightcurve point that was inspected by user. * The internal copy of CFITSIO library is updated to v3.370. * Introduced VaST testing script util/examples/test_vast.sh Beware, the script will download ~1.5Gb of test data! If you have fast internet connection, you are welcome to run this test script. Please write me if the test script reports any problems. 27 May 2015: vast-1.0rc71 * Restored the PSF photometry mode. It requires PSFEx and a recent SExtractor version 2.8 or later to work. Unfortunately, PSF fitting cannot be performed with the old Sextractor-2.5 supplied with VaST, so you'll need to manually install a newer SExtractor and PSFEx in your system. Please consult PSFEx manual to learn about PSF extraction parameters set in default.psfex These parameters will most likely require fine tuning for your images. To start VaST in the PSF photometry mode: ./vast -P ../sample_data/f_72-0* * Instead of just displaying the familiar mag-sigma plot, ./find_candidates can now also plot the following variability indexes as a function of magnitude: + Weighted sigma divided by the number of points in the lightcurve. The idea is to artificially hide the lightcurves having large sigma but only a small number of measurements. The weighting scheme follows Stetson (1996) attempting to downweight outlier points in a lightcurve. + Stetson's L variability index as defined in the 1996 paper + Robust Median Statistic (RoMS) as defined by Enoch, Brown & Burgasser (2003) + The simple "peak-to-peak" variability index suggested by Aller, Aller & Hughes (1992) The peak-to-peak index is defined as v = ( ( M_max - error(M_max) ) - ( M_min + error(M_min) ) ) / ( ( M_max - error(M_max) ) + ( M_min + error(M_min) ) ) so it can be negative if the observed lightcurve scatter is lower than estimated errors. Use 'M' and 'N' keys to switch between the plots. For all the plots, a higher value generally indicates that an object is more likely to be variable. * The default SExtractor parameter files are changed to use "XWIN_IMAGE, YWIN_IMAGE" star positions instead of "X_IMAGE, Y_IMAGE". It should result in an improved astrometric accuracy at the cost of slightly longer computing time. See Section 10.2 of the "official" SExtractor documentation for details. * The internal FITS viewer ./pgfv now supports 32-bit images that lack BZERO keyword in the header. * The internal FITS viewer ./pgfv can now handle images with a narrow range of pixel values like from 0.0 to 1.0. * The internal FITS viewer ./pgfv can work with files having a white space in the name. * The internal image viewer ./pgfv, if started from the lightcurve inspection tool ./lc, will automatically zoom-in on the star of interest. You may see the full image by pressing 'D' or 'Z'+'Z' to zoom-out. * Renamed ds9 region file from vast_list_of_all_stars.ds9 to vast_list_of_all_stars.ds9.reg in order to prevent ds9 from trying to open it automatically each time it starts. The proper way to use this file would be ds9 /path/to/reference/image.fits -region vast_list_of_all_stars.ds9.reg * VaST now supports FreeBSD operating system. Tested on FreeBSD 10.1 with gcc. Changes are introduced in an attempt to allow VaST to handle HST Level 1 (exposure) images from the Hubble Legacy Archive: * Image date can now be set from EXPSTART key containing MJD(UTC) of the exposure start. * VaST is trying to guess the saturation limit for each image as guessed_saturation_limit=maxval-SATURATION_LIMIT_INDENT*maxval where maxval is the brightest image pixel and SATURATION_LIMIT_INDENT is set in src/limits.h. By default SATURATION_LIMIT_INDENT=0.1. This behaviour may be turned on by running ./vast with -g option or off by using -G option. If none of the two options is specified explicitly, VaST will make a wild guess if it should use SATUR_LEVEL specified in default.sex or if it should try to guess it for each image individually. * VaST will check how many pixels having the value of exactly zero are in the input image and if there are more than FRACTION_OF_ZERO_PIXEL_TO_USE_FLAG_IMG*total_number_of_pixels the program will automatically produce a flag image for SExtractor to filter-out stars overlapping with these bad pixels. The value of FRACTION_OF_ZERO_PIXEL_TO_USE_FLAG_IMG can be changed in src/limits.h. Make sure to run 'make' after updating src/limits.h for the changes to take effect. 11 Mar 2015: vast-1.0rc70 * Automatic choice of a VizieR mirror. * VaST can now handle filenames with white spaces if they are specified in the command line (but not in the vast_list_of_input_images_with_time_corrections.txt file, sorry). * VaST is trying to guess the field of view of an image (for plate solving) if it was not specified explicitly. The guess is based on a previously-solved image of this same field or on the FOCALLEN key in the FITS header (assuming it contains focal length of the telescope expressed in mm). * If a blind plate solution failed with a specified (or guessed) field of view, the program retries to solve the image assuming a larger or smaller field of view. 7 Mar 2015: vast-1.0rc69 * The program can now again work with VizieR. * Astrometric calibration of images can now be performed using one of a few plate-solving servers (the best one is be chosen automatically) or using a local copy of Astrometry.net software (if it is installed in the system). * Improvements in the plate solving algorithm. * VaST FITS image viewer (./pgfv) now remembers image orientation (set by pressing 'V' and 'B' on a keyboard) after changing zoom (keyboard 'Z'). * The magnitude-scatter plotter if started in the non-recompute mode (./find_candidates aa) will now remember stars viewed by user earlier (indicated as green points on the plot). * While performing a manual magnitude scale calibration with util/magnitude_calibration.sh it is now possible to cancel the input by typing 99 instead of an actual star magnitude. This is useful in case one selected a wrong comparison star. * The magnitude calibration routine is now trying to guess if parabola or the "photocurve" provide a better approximation of the "measured mag."->alog mag." plot.elation. One can always override the automatic choice by pressing 'P' while looking at the "measured mag."->"catalog mag." plot. * Fixed the bug that prevented lib/vizquery from working properly if cdsclient is not installed system-wide (wwwget was missing from $PATH). Now VaST includes a fully self-contained copy of cdsclient. * VaST now supports images obtained with the SBG camera of Kourovka Astronomical observatory (Ural Federal University) that have a non-standard FITS-like header. * Updated tai-utc.dat file includes the leap second to be inserted at the end of June 30, 2015 at 23:59:60 UTC. (This is needed for accurate UTC->TT conversion after that date.) 17 Jun 2014: vast-1.0rc68 * The program can now again access VizieR. This feature was broken because of the change in order of output columns printed by vizquery script. Star identification scripts now work again. :) * The Kwee - van Woerden (1956BAN....12..327K) minimum finding method built into the VaST lightcurve viewer (./lc) now returns the full JD, not the one relative to the lightcurve start. To activate the Kwee - van Woerden algorithm, press 'K' in the lightcurve inspection window. * The input images may now be specified not only as command line arguments, but also listed in the file vast_list_of_input_images_with_time_corrections.txt located in the VaST directory. The file should have two columns: absolute or relative path to the image file and time correction in seconds that should be applied to the file (in most cases should be 0.0). Full JD of the image may also be specified instead of the time correction. That will override JD determined from the image FITS header. VaST will guess what it is based on the specified value. See examples in vast_list_of_input_images_with_time_corrections.txt_example * Instead of specifying each image on the command line or in the vast_list_of_input_images_with_time_corrections.txt file, it is now possible to give a directory name as a command line argument. VaST will process all FITS images found in the specified directory, but it will not look recursively into sub-directories. Note that if only the directory name is specified, user has no control over which image in this directory is processed first and, therefore, used as the reference image. It is possible to mix all three input methods (individual images specified in a command line, vast_list_of_input_images_with_time_corrections.txt file and directories specified in a command line) in a single VaST run, so one can specify the first (reference) image explicitly on the command line. * Fixed the bug causing segmentation fault when input images have different size. Note that the input images may have different size in pixels, but still have to have the same scale ("/pix) in order to be processed in a single VaST run. * Minor improvements in the image matching algorithm resulting in a ~10% speed-up on a typical dataset. 13 May 2014: vast-1.0rc67 * Fixed the bug that caused "buffer overflow" crash on long image series (of a few thousand images). * New routine provides a locally-corrected astrometric position for each object on an image. The astrometry is based on UCAC-4. The routine may be called directly as util/solve_plate_with_UCAC4 myfitsimage.fits 40 (here myfitsimage.fits is the FITS image file name, "40" is the approximate field of view in arcminutes) to produce a list of sources on the given image. A better way to benefit from it is by using the automated identification script (util/identify.sh or 'U' key in the lightcurve inspection window) and (hopefully) enjoying the much-improved astrometric accuracy. This new astrometric routine needs Internet connection to work, but the identification script needs it anyhow... * It is now possible to use APASS magnitudes listed in UCAC-4 to calibrate the instrumental magnitude scale. Use the script util/magnitude_calibration.sh R 40 (where "R" is the observing band/filter and "40" is the approximate field of view in arcminutes passed to the plate solution routine). The choice of observing bands is the following: + "C" for "clear" are the unfiltered UCAC-4 magnitudes + "B" are the APASS B magnitudes + "V" are the APASS V magnitudes + "r" are the APASS r magnitudes + "i" are the APASS i magnitudes + "R" are Rc magnitudes computed from APASS V, r and i following Jester et al. (2005), see http://www.sdss.org/dr4/algorithms/sdssUBVRITransform.html Choose the scale that best matches your observing band. "R" is the usual choice for unfiltered CCD chips, "V" may be appropriate for unfiltered blue-sensitive CCD chips and green-channel of DSLRs, "B" may be good for blue-sensitive photographic plates. The old version of the magnitude calibration script is renamed to util/magnitude_calibration_USNO-B1.0.sh * Internal copies of libraries are updated to CFITSIO v3.360 and gsl-1.16. * Plate solution details (such as field of view size and its center) are now printed out in a terminal. * Improved Aladin script that generated and launched if you have Aladin installed locally. The script now displays both DSS and the original input images. This may be useful to visually confirm identification of an interesting object. The star suggested as a correct identification by the automated procedure is clearly marked in the Aladin plot. * Server-side plate solution software is upgraded to astrometry.net-0.46 which (in a combination with new index files produced from Tycho-2 and 2MASS catalogs) provides considerably better solutions of some badly distorted images (think telephoto lenses and wide-field photographic plates). Silly enough, it turned out that previous versions of the VaST plate solution routine cannot handle the long FITS header produced by astrometry.net-0.46. Please upgrade to vast-1.0rc67 if you conduct plate solutions from within VaST. 27 Mar 2014: vast-1.0rc66 * Fixed the script performing absolute magnitude calibration (util/magnitude_calibration.sh). It was broken by a change in the output format of vizquery. To calibrate the magnitude scale using USNO-B1.0 B magnitudes as a reference you may execute: util/magnitude_calibration.sh B to do the same using R magnitudes from USNO-B1.0: util/magnitude_calibration.sh R * Fixed a problem preventing VaST from compiling on some virtual machines when "gcc -march=native" cannot correctly recognize the processor architecture. * Fixed a problem preventing VaST from starting on a system that is low on RAM. Now, if there is enough memory to process the data - VaST should be able to use it efficiently. * New log files vast_list_of_all_stars.log and vast_list_of_all_stars.ds9 contain pixel coordinates of all detected stars in thee list formated as a region file that can be loaded into the ds9 FITS image view list wile vast_list_of_all_stars.ds9 is the same list formated as a region file that can be loaded into the ds9 FITS image view list wile vast_list_of_all_stars.ds9 is the same list formated as a region file that can be loaded into the ds9 FITS image viewer. 29 May 2013: vast-1.0rc65 * Added linear magnitude correction as a function of star position on a frame. This is useful to correct extinction on very wide field (a few degrees) images such as those obtained in the NMW survey ( http://scan.sai.msu.ru/nmw/ ). By default, the program will turn on this correction if the reference image has more than 10000 stars on it. You may manually turn this correction on (off) by starting VaST with "-j" ("-J") flag. If you have wide field images, try to experiment with this option and see what works best for your data. * The star matching algorithm is now allowed to use saturated and blended stars for image identification. This slightly degrades the quality of the initial plate solution, but that is corrected for at a later stage. The good thing is that this change makes the algorithm much more stable and it typically requires less reference stars to match images. The image matching process becomes faster. * Fixed broken links to WISE-Atlas in the transient detection mode. * Fixed the lightcurve viewer (./lc) crash when one tries to delete the first point from a non-VaST-formatted lightcurve. 13 Apr 2013: vast-1.0rc64 * "Official" support of the transient detection mode. The code was there for quite some time, but was lacking documentation and had to be tested extensively. The code is still FAR from perfect, but I believe it may already be useful. See the VaST home page for details. * A major bug that prevented stars with very large sigma from appearing on the sigma-magnitude plot is now fixed. Thanks to Fidrich Robert for discovering it! * "JD" keyword is read form a FITS header only if "DATE-OBS" keyword was not found. Useful for FITS files that have both keywords in their headers. * Fixed an issue that prevented VaST to compile on Mac OS after the latest development environment update. Thanks to Alexei Alakoz for his valuable help in testing! * A new script util/catalina_search_area_TEST.sh is introduced that allows to search Catalina Sky Survey data in a small area around a particular sky position. The data may be processed using standard VaST tools. The current implementation of the script is very slow and is meant only for testing and feasibility studies, it is not ready for mass-processing of CSS data. * An automatic-testing script lib/test_vast_release.sh is introduced. It currently works only with a system-wide installation of SExtractor 2.8.6 and consumes tens of megabytes of Internet traffic. But, if this is not a problem - you are welcome to try it! * Minor bug fixes. 16 Jan 2013: vast-1.0rc63 * Fixed the major bug that caused the new star matching algorithm (introduced in vast-1.0rc62) to fail to match some stars in close pairs. The problem was evident on large datasets when the program got swamped by unidentified stars, while the older versions of VaST could handle these datasets. I am deeply grateful to E. G. Lapukhin for spotting the problem. Thank you! :) * The program now uses internal versions of PGPLOT and GSL libraries, so users do not have to worry about installing these libraries system-wide. * VaST now comes with a built-in SExtractor v2.5. It is still recommended to use a system-wide installation of a newer SExtractor version, but now, if VaST fails to find "sex" executable in the $PATH, it will use the internal one. This might be helpful for those who have problems compiling new SExtractor or, more likely, ATLAS libraries on which the new SExtractor depends. * Individually processed images may now be viewed with DS9 instead of the internal VaST image viewer: ./sextract_single_image -9 image.fits * Fixed the bug that caused VaST not to create vast_stars_with_large_sigma.log file when used with gsl-1.15. * VaST was successfully tested on MacOS X 10.8.2 'Mountain Lion' + XQuartz, Xcode, MacPorts -> gcc (including gfortran and g++), wget (resolution is fine with a retina display). * Internal CFITSIO library upgraded to Version 3.31. Overall, if one has a Linux or Mac system with a working development environment based on gcc, the new version of VaST is supposed to just compile and work, with no need to manually install additional libraries and programs. How well does it work in real life? Well... Bug reports and success stories are welcome, as always! ;) 28 Oct 2012: vast-1.0rc62 * Improved star matching algorithm resulting in ~2x overall performance increase on large datasets. * The online period search interface ("L" in the lightcurve inspection window) tries to set reasonable maximum and minimum trial periods automatically. * All lightcurves inspected with the online period search service are saved locally in the "saved_period_search_lightcurves/" directory, so it's easier to find them later. 28 May 2012: vast-1.0rc61 * The new experimental feature in vast-1.0rc61 is its integration with the online period search service. You may try it by pressing 'L' key at the lightcurve inspection window (./lc). The lightcurve will be sent to a remote server for analysis and a browser window will open displaying the results. Naturally, this feature requires an active Internet connection to work. You are also welcome to try the period search service as a stand-alone web-application by pointing your browser to http://scan.sai.msu.ru/lk/ * The bug is fixed which caused VaST to crash on images that have no comment field for the DATE-OBS key in the FITS header. * Improved stability of the magnitude calibration solution in "difficult cases". * The new version contains a local copy of the vizquery script from cdsclient-3.7 package. No need to install cdsclient, for the automatic star identification (e.g., "util/identify.sh out01234.dat") and magnitude calibration (e.g., "util/magnitude_calibration.sh R") scripts to work. * VaST correctly handles the situation when it cannot create child processes (for example, because the system runs out of memory) during the execution of the main program. * vast-1.0rc61 compiles on the latest version of Ubuntu. Please check also the updated instructions for Ubuntu users at the VaST homepage: http://scan.sai.msu.ru/vast/#down Frequently Asked QuestionsHow to perform differential photometry with VaST? How to obtain a lightcurve of an individual object with VaST? VaST doesn't detect my target source. What's wrong? VaST doesn't run complaining that no images are found. Which Linux distribution is suitable for VaST? Is there a Windows version of VaST? VaST cannot match images in the input series. How to minimize the detection of stars near the edge of the field? What exact metadata from the FITS image VaST needs, other than the image itself? Exposure time? VaST calibrates the magnitude scale as a part of data processing... How exactly is this done? Is aperture photometry that VaST does enough in most cases, or should I do PSF-fitting photometry? How to acknowledge VaST in a publication? List of publications which make use of VaSTIf you are aware of a publication not listed here, please drop me a line at kirx[at]scan.sai.msu.ru so it can be include it in this list.
Variable star search software not related to VaSTIf VaST doesn't suit your needs, you may be interested in trying other software:
Other tools that might be useful
If you have any questions fell free to contact VaST authors via e-mail kirx[at]scan.sai.msu.ru
Good luck in using VaST! VaST developers team. | ||||||||||
VaST developers team, 2005-2015
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