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Displaying MAST Spectra

This tool displays selected spectra or light curves from missions archived within MAST. It uses the HTML5 Canvas API for drawing graphics. Canvas is supported by the latest versions of all popular browsers including IE 9, but it is NOT directly supported by IE 6,7 or 8.

With Canvas and javascript, most of the plotting options can be run locally on the users computer and therefore can be executed fairly quickly. Reloading the page or clicking the "Start again" button will retrieve the data from the MAST web server, which takes a little longer, but allows you to return to the original display.

Note: to reset parameters to their initial values, click the shift key which clicking the reload button. Clicking "Start again" will re-display the original spectra, but some javascript-based options may remain unchanged.


  • Clicking "Start again" will replot the data and reset all parameters to their default values except for Kepler light curves for which the data type remains unchanged. Write down scale factors if you want to save them.
  • For Kepler previews, clicking "Back to previous quarter" will display the previous page displayed in the same browser window.
  • For spectra dominated by a few bright emission lines, it may be hard to zoom in on the continuum if it lies close to the minimum flux value. To make it easier to zoom in, first decrease the "Min Flux" value.
  • When plotting multiple spectra, you can use the scale factor to help identify individual spectra. For example, changing a particular scale factor from the default 1.0 to 1.1 will cause that particular spectrum to stand out. Changing individual plot colors also works.
  • To quickly remove a spectrum from a multi-spectrum plot, set its scale factor to 0.0. Resetting it to 1.0 or clicking "start again" will restore it. For more permanent removal, delete the file name from the "Selected File(s)" window. This will remove it until a new plot is drawn from the search results page.
  • To save a plot, either click the "Create png image" button, or do a screen capture of the original page. Note the png image appears to have a black background but it will appear gray when you save it to disk. When printing, the background color will not appear.
  • When plotting multiple spectra/light curves, widening the browser window slightly may help organize the scale factor list.

Source of Data

The data available for plotting comes from various sources. The files used for the various MAST missions are as follows:
  • Kepler - Data is extracted from the online (public) FITS light curve files produced by the Kepler project. Bothe the PDCsap and the Sap Flux vectors are plotted by default.
  • K2SFF - Fluxes and times are extracted from the FITS files produced as a K2 High Level Science Product by Andrew Vanderburg at CFA. Both raw and corrected fluxes are displayed, with "bad" points removed.
  • K2VARCAT - Fluxes and times are extracted from the FITS files produced as a K2 High Level Science Product by D. J. Armstrong et al. at the University of Warwick, UK.
  • HST - FITS preview files created at CADC
  • IUE - ASCII preview files created by NSSDC
    Note that small aperture observations will only be displayed when there is no corresponding large aperture observation. If both double aperture exposures are submitted for plottng, the large aperture spectrum is displayed twice.
  • FUSE - ASCII preview files created by MAST(?)
  • TUES - merged ASCII preview files created by MAST
  • BEFS - merged ASCII preview files created by MAST
  • EUVE - FITS "spectral container" files created by MAST
  • WUPPE - FITS "spectral container" files created by MAST
  • HPOL - FITS "spectral container" files created by MAST
  • HUT - FITS "spectral container" files created by MAST
    Note: only the first HUT spectrum is plotted for those cases where two are stored in the same file.