H..4.8 Can I use GBTIDL with data from telescopes other than the GBT?

If the data are in UniPOPS format you can use the uni2sdfits procedure (see details at the end of this answer). Otherwise, GBTIDL provides no tools for converting data from other telescopes. However, with a little work on your part, it should be possible to get spectral line data from any other telescope into GBTIDL. There is even some chance that if your data follow the SDFITS convention that GBTIDL will be able to read it directly.

The easiest way to import generic data into GBTIDL is to use standard IDL tools to get the data into a data container, as described below. You can then use GBTIDL to operate on data in data containers, and you can save the data containers to SDFITS format as well.

A data container is just an IDL data structure with a predefined format. See the 'About Data Containers' section for a discussion about data containers in GBTIDL. You can get data into a data container as follows:

• Read your data values into an IDL array (e.g. use READU to read unformatted binary values or mrdfits to read FITS tables, or import the data from an ASCII file using readf)
• Create a new data container to hold those values: dc = data_new(myvalues)
• Set the associated header fields in dc, for example:

  dc.source = 'mysource'  
  dc.scan = 24  
  dc.coordinate_mode = 'J2000'  
  ...
  

• Copy dc to the primary data container:

  set_data_container, dc
  

• Save it to an output file:

  						
  fileout,'myfile.fits' 
  keep
  

• Free the memory used by the data container:

  data_free, dc
  

• When you return to look at this data in a later session, you can load it into GBTIDL directly from the SDFITS file as follows:

  start a new GBTIDL session first

  						
  filein,'myfile.fits' 
  getrec, 0
  

Pointers:

• When setting the header fields in dc, pay particular attention to those related to the frequency axis and its conversion to velocity.
• If you are going to be using set_data_container repeatedly, use freeze to speed up the operation.

Please contact us with any questions about the contents of the data container or other aspects of GBTIDL necessary to do this translation. (However, please be advised that we have limited resources, and will not be able to provide extensive development for reducing data from non-NRAO telescopes.)

As an example, the contributed procedure uni2sdfits uses an IDL class sdd to read in the UniPOPS binary file and then the above steps are used to copy it to the primary data container and keep it to the output file. The source code can be seen by clicking on the "source" links at the top of the page in each of the above two links.