Table of Contents

  1. Introduction
  2. GUI - Main Window
  3. Create SSAP VOTables
  4. Analysis Tools
  5. Fitting Utilities
  6. SED Spectra
  7. Photometric services
  8. Simple Line Access
  9. Theoretical Access
  10. Interoperability
  11. VOSpec Guys
  12. References
  13. User Feedback

GUI - Main Window

ALL the image area is cliccable

Clear Cache View Plot Full Size Graphic Options
Click on the image area for explanations

New feature!!
Flexible JTable to show and order Spectra List according to METADATA tags.

Click on the JTable icon to switch from JTree to JTable and viceversa.

All the spectra can be ordered according to any metadata, just by clicking on the metadata name.
The table can be extracted and expanded in a convenient way.
Also all the columns can be ordered just by clicking on them.

Target Search
Input the name of the object to be searched. Whenever the “Go” button is pressed, the VOSpec will contact the SIMBAD Web Service to resolve the name (see for more details)

Right Ascension in decimal degrees

VOSpec admits the following string coordinates formats for RA:

DD.DDD (Degrees)

DD:MM:SS.SSS (Degrees, Minutes and Seconds)

DDh:MM:SS.SSS (Hours, Minutes and Seconds)

DDd:MM:SS.SSS (Degrees, Minutes and Seconds)

DDh:MMm:SS.SSSs (Hours, Minutes and Seconds)

See IVOA SSAP specification for details.

Declination in decimal degrees

VOSpec admits the following string coordinates formats for DEC:

DD.DDD (Degrees)

DD:MM:SS.SSS (Degrees, Minutes and Seconds)

DDd:MM:SS.SSS (Degrees, Minutes and Seconds)

See IVOA SSAP specification for details.

Size in decimal degrees

See IVOA SSAP specification for details.

This is what is called the Region of Interest. From the Simple Image Access Specification.


[…] Region of Interest.
The position of the region of interest, expressed as the right-ascension and declination of the field center, in decimal degrees using the ICRS coordinate system […]
The angular size of the region given in decimal degrees. The region may be specified using either one or two values. If only one value is given it applies to both coordinate axes. If two values are given the first value is the angular width in degrees of the right-ascension axis of the region, and the second value is the angular width in degrees of the declination axis. Note that the angular width along the right-ascension axis is not the width of the region in right-ascension, which is equal to the angular width divided by cos(DEC).
[…]The default image size is service-defined and may be a value considered appropriate for the service, for the given image or data collection being accessed, or for the object (if any) at the given position.
These parameters define a nonrotated, rectangular region on the sky, having the specified angular extent in right ascension and declination, using the Cartesian (CAR) projection with the region center (POS) as the reference point. The Cartesian projection is used here as it is simple and can scale to the whole sky, and works about as well as anything else for small regions. Note: the use of the CAR projection to define the ROI has nothing to do with what projection we choose for any actual generated images.



Log scale selector

Click box to select-unselect log scaling of both axes

Fitting algorithm window
See Fittings Utilities Section for more details on the fitting algorithms

Please click on tabs to be redirect to the relative section

Wavelength unit
Given here are some standard wavelength/frequency units used for multi-wavelength display and superimposition. The reference wavelength unit (chosen arbitrarily) against which all the units are converted using the dimensional analysis algorithm (see References) is the Angstrom.

Flux unit
Given here are some reference flux units used for multi-wavelength display and superimposition. The reference flux unit (chosen arbitrarily) against which all the units are converted using the dimensional analysis algorithm (see References) is the Jansky.

Rest-frame correction
Insert redshift to shift the spectrum to the source rest frame.

Wavelength to Velocity Analysis
Convert Wavelength to Velocity

Activation button for unit conversion tools

Spectrum color indicator
When clicking in this colored button, the spectrum plotted with that colour will be shown isolated from the rest, and in the spectrum information display, the row corresponding to the spectrum will be highlighted.

Plot symbol
Choose between different plot symbols: points, dots, lines.

Select the part of the spectra to be cut

Spectrum display selection
To display several spectra at the same time, click the checkbox corresponding to the spectra.

Change plot features: title, X-label, Y-label, colors...

Activation of Spectrum Display selection
Activates the display with the settings made in the “Graphic Mode” window. When no spectrum is selected in any of the check boxes, all of them will be displayed. The “View” action does not reconnect to the servers to get the information.

Clear cache
The VOSpec implements a caching mechanism to save download times whenever a spectrum is requested several times. Under certain circumstances, the cache has to be cleaned (sometimes caused by server unavailability after a certain spectrum was previously successfully retrieved, etc.). Activate this button to clear the cache directory.

Unzoom button
Will reload completely zoomed-out spectra.

Spectrum Selection Box
Click check boxes of spectra to be displayed.

Spectrum Information Display
Gives the available information (compulsory fields in the SSAP response) for the available spectra. Clicking twice anywhere along the row, a new small window will appear with all the available metadata (whether SSAP compulsory or optional) for the spectrum. It also allows to save the spectrum in its original format.

General Display Window
Plot window where the spectra will be displayed. Standard general utilities for plot windows are available, like display selection zoom-in and zoom-out.

Display activation button
Clicked after the selection is performed to display the selected spectra

Analysis Tools
Please visit the section Analysis Tools for more details

Connect to Plastic Hub
Please visit the section Interoperability for more details

Resets all selected spectra check boxes and cleans main display window (20).

Save image
The image (SED or single spectrum) appearing in the general display window can be saved using this button either as image or as VOTable. In a near future, FITS and SED format will also be available.

Open SSAP Wrappers and Spectra

File formats supported:

VOSpec supports specially well and encourages the use of the IVOA Spectral Data Model:

thanks to the NVO SED library (
For the moment, only serializations in VOTable are supported.

Furthermore, any spectra in the following formats is supported:


- Binary tables (2 columns, for wavelength and flux)
- ASCII tables (2 columns, for wavelength and flux)
- 1D FITS spectrum images. Definition here.


- 1.0 REC
- 1.1 REC

Please visit the section Create SSAP VOTables for more details

Open locally a SED (Spectral Energy Distribution) spectrum with the NVO SED library.


Connection to Registry
When clicking “Go”, VOSpec will connect to any of the available harvestable full registries (see IVOA specifications for registries at and will ask for services giving SSAP access to their data. The list of registries to which the VOSpec will connect is written in as configuration file.
After clicking on the “Go” button, a Server Selector window will appear:

Server Selector is an advanced tool to perform queries in the VO.
It gives a list of the Registered Services (alphabetically ordered) whose Service Type is “SSAP” and "TSAP".
The user will select those services he/she is interested in and can also make queries by parameters. As soon as you select one param, all the services supporting that param will change color to green. Remember to select one or more services to perform the query, if it turns green it doesn't mean it is selected.
When a param is selected you have the possibility to insert its value in the related field (bottom on the right).
If two or more params are selected, it will turn green just those services supporting all those params selected (intersection function).

New feature!!

In the case the user is interested in displaying his/her own Local Service this can be done by the option "Add SSA/TSA", which temporarly add your service to the list in order to be tested.

See Create SSAP VOTables for more on how to create an SSAP Wrapper around your files.

Refresh Button will help to check for new services registered in the ESAVO Registry (


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