ASERA, A Spectrum Eye Recognition Assistant, is a semi-automated toolkit developed to improve the efficiency and effectiveness of spectral classification. While the template spectra are superimposed on the observed spectra, it will be easy to find the best match between the two spectra, via dragging and clicking the mouse to adjust the redshift and flux scale arbitrarily. Then we will get to know if the observed spectra is the spectra from a star, galaxy or QSO, and the redshift which is applied to the template spectra.

Spectral type recognition is the fundamental step for people to know the basic properties of a celestial body (Teff, Logg, [Fe/H], et al.). ASERA will be of great help when you are inspecting a large number of spectra, like from LAMOST (the Large Sky Area Multi-object Fiber Spectroscopic Telescope) and SDSS (Sloan Digital Sky Survey).

The toolkit is free of installation. All you need is to download the JAR file and start it with Java Virtual Machine (JVM).
If your operation system has built the link between .jar files and JVM program (like in MacOS), a double click if is enough. Otherwise you need to go the the directory where the ASERA JAR file is placed and type this word in command line: java -cp [jarfilepath] ImagePanel. Make sure the "java" command is available, which can be checked by type command "java -version". The JVM is available and free of charge for MacOS, Windows and Linux from

If you have any trouble with the installation, email:


If the ASERA toolkit was helpful for your research work, the following acknowledgment would be appreciated:
This research has made use of the ASERA toolkit, 2013A%26C.....3...65Y, "ASERA: A spectrum eye recognition assistant for quasar spectra", Yuan H.-L. et al.

Features and updates

Features: adjust redshift and flux, smooth, line fit, templates(Star of OBAFGKM/Carbon types, galaxies and QSOs).

Click ASERA to download software. Here are some fits file samples from LAMOST: spectra1, spectra2, spectra3, spectra4 and spectra5. (last update on 20141103)

Add frame resize and mouse wavelength zoom in ability; fixed some bug in reading LAMOST and SDSS fits file (use right click-->input file format to choose input file type). (last update on 20150109)

Add Lorentz profile absorption line fitting. (last update on 20150415)

At startup, one can drag a range to zoom in waverange and double click to resize; press "T" or click the checkbox at lower left corner to switch into the template drag mode. (last update on 20160101)

Now you can drag a file into the window of ASERA to open it. (last update on 20160414)

By providing a asera_config/grayzone.txt at the location of ASERA JAR file, use can show a gray problem region in the spectral window. (@20160421)

The version 3.0 is presented with over plotting ability. (@20160629)

Stellar parameter estimation is supported now via calling ULYSS. (@20160812). One can start parameter estimation by "Right Click -> ULYSS PARAM". Check UlySS manual for more detail.

Update mysql database read/write ability for both redshift match and ULYSS. (@20161008).

Add a common fits spectra reader. (Usage: right click--input format--FitsCommon). User can change configuration by add a file named "./asera_config/FitsReader_Common.ini". Here is an example. New version can be download from here. (@20180117).

Quasar template

The median composite quasar spectrum template from SDSS (Vanden Berket al., 2001).

Basic Theory

Assuming the unrecognized target spectra is hold in the left hand, the template spectra is overlapped on the target spectra with the right hand. By adjusting the redshift hourizontally and the flux ratio vertically via the mouse clicking, dragging and scrolling, one can easily figure out the best fit and provide the apt redshift value if the observed target is a quasar.

Redshift z is calculated as , where is the wavelenght of the reference line of the template spectra in the rest frame and is the current wavelength of the reference line of the template spectra after redshift adjustment.

Supported Input File Formats

Supported input files include: image files, like *.PNG, *.JPG, *.GIF and et al; LAMOST fits file; SDSS fits file.

To support more formats user can contact the author to update the specific implementation of the FITS file reading interface.

For fits file, user can click "H" button to view fits header.

Software Interface

Main interface of ASERA.

ASERA offers a single main window for displaying and manipulating the data, as shown in Fig. 2. The combined functional regions are discussed as follows:

  • Region 1: the input data resource path and the path specification buttons.
  • Region 2: the target and template spectrum in the centric viewport. The final redshift $z$ of the template spectrum is printed at the lower-left corner. A set of spectral lines are plotted together with the template spectrum at the same time.
  • Region 3: the most important information of the target including RA, DEC, target name, target type, SNR, magnitude, et al.
  • Region 4: a button group for scaling and shifting flux range of the viewport for the target spectrum. It helps the user to acquire a proper flux density range for inspection.
  • Region 5: a button group for scaling and shifting wavelength range of the viewport for both the target spectrum and the template spectrum. It helps the user to acquire a proper wavelength range for inspection.
  • Region 6: the mouse right click popup menu. It provides a set of functions including template spectrum selection, visible absorption/emission lines selection, redshift \textbf{reference line} selection, image saving, pixel-wavelength conversion starting and end point specification. The current pixel-wavelength conversion status is displayed in the bottom line of the main window.

The adjustment of the flux density of the template spectrum is handled by mouse. A left mouse button click event will replace the flux zero point and the reference line of the template to the clicked position. Then the redshift $z$ will be recalculated and the spectrum will be repainted. A left mouse button drag event will shift the flux zero point and the reference line according to the drag distance. The mouse scrolling event will change the flux scale.

Basic Features

Flux adjustment is supported by the buttons on the up-left side of the main window, see region 4 above.

Wavelength adjustment is supported by the buttons on the lower-right side of the main window, see region 5 above.

Use "right click --> SMOOTH" to set number smooth steps. Default value is 1, meaning no smooth is applied.

Use "right click --> Set spec start/end" to setup pixel-wavelength(unit:angstroms) transformation for image files. Current transformation parameters are printed at the bottom of the main window.

Use "right click --> Z alignment line" to select the reference line.

Use "right click --> Save Image" to save current interface as PNG file.

Supported templates

Not only quasar can be recoginized using ASERA. Supported templates include:

See: SDSS templates.

To invoke template selection: right click --> plot template.

Show Spectral lines

Several sets of spectral lines can be displayed together with template spectra in this window.

To invoke the window: right click --> plot lines.

Batch process

Several batch process features are added:

  • Open local directory and scan all files in the directory one by one.
  • Open CSV file, of which the first column of each line indicates the URL of spectra of one target.
  • Open local VOTable XML file containing spectral URLs.
  • Open VOTable response from Online IVOA-SSAP service.
  • Cowork with MySQL database & Http server.

Results can be saved to and loaded from local textual files.

Click the "+" button to invoke this window.


Short name: ASERA
Full name: A Spectrum Eye Recognition Assistant for Quasar Spectra
Author email:
Software copyright number: 2014RS036589
Reference article:

The software, ASERA, is allowed to be used, modified and republished only for academic research purpose.
It is appreciable that the reference article mentioned above is cited in user's work.
Any software bug feedback and update suggestions are welcome.

This software has made use of the following third part packages: the MySQL Java Connector, the Apache Commons Math library, the nom.tam.fits library and epsgraphics library.