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Using Specview in the AVO demonstration tool

Status Jan 2004

For AVO purposes we use the beta version of Specview 2.7 which has been created by Ivo Busko at STScI (many thanks). It is included in AVO-Aladin and starts automatically when suitable spectra are selected.

Note that this is under development and more sophisticated functions may appear in future. The source code package is also available.

In addition to the standard functions, this version

• Displays ISO LWS data correctly and allows its manipulation
  • This works on most spectra with the lsan prefix
  • Select desired spectrum from AVO-Aladin (SSA discovery)
  • Select all or chosen segments from pop-up
  • Click on DQ button and then select ALL to get a clean plot
  • You can fit models etc. as usual - here is a test xml model file you can load with Model Manager to make a 2-component fit with a Planck + powerlaw function. Warning this may not be meaningful if the data are not fully calibrated.
  • Data taken a raster need different treatment
• Measure the flux at any wavelength and writes the output as ascii into a file. Warning this should be used with caution if the data are not fully calibrated.
  • Display spectrum in Specview as above (or as appropriate for other data)
  • Select "Cursor" menu and choose Open log file (suffix .log is automatically appended). At this point cursor logging is enabled.
  • Move the cursor to the required wavelength on the spectrum.
  • Every time you press the CTRL key on your keyboard, the cursor display windows at top center will flash in green, and their contents will be written to the log file.
  • When you have finished, Select "Cursor" menu and choose Close log file. Only at this point is the log file is written to disc (so you can't inspect it before closing).
  • Openning an existing log file inside Specview will erase its contents and start logging afresh.

The log file is an ASCII text file that stores a single cursor value at each row. For now, cursor values are comprised of the X and Y coordinates and their respective units. Here is an example:

It is necessary to carry units information into the log because the user may change the units at will during a logging session. The software at the receiving end should be aware of that, I think. At this point the cursor file carries no other information about where the readings are coming from: which file, which specific spectrogram within a given file, which data arrays, etc. These may be added later in the game.

The log file may then be loaded directly with the AVO-Aladin MyData load window, this will start VOPlot and the data can be manipulated e.g. to make colours as desired.

AnitaRichards - 30 Oct 2003