A blog named for the muse of Astronomy containing musings by an astronomer

Announcing External SPECROAD… woot!

Posted on August 11, 2008 by Juan

A few folks have been aware that I am involved in an interesting project to determine the “Shape of our Galaxy”… specifically the nature of the asymmetries observed in the Thick Disk stars in the galaxy. Part of that project involved obtaining multi-fiber spectrograph observations of many stars in selected fields of the sky using the Hectospec multi-fiber spectrometer on the MMT on Mount Hopkins.

Unfortunately, there are very few “external” users of the Hectospec, so the software pipeline available for reducing Hectospec observations, called SPECROAD, was only geared to run on SAO computers. I spent a considerable amount of time last summer and this summer getting that software into a much more portable form, documenting how to use it, and removing bugs from the code.

All this work resulted in the creation of a new version of the Hectospec data pipeline I dubbed “External SPECROAD” or “E-SPECROAD” for short. There were several major problems with the original SPECROAD code that I addressed in E-SPECROAD:

  1. Nonportability: The SPECROAD scripts were only designed to run on a Solaris computer at the SAO, with files in specific hard-coded locations using a specific IRAF environment with all the IRAF parameters set before the scripts were run. This has been addressed by trying to assume almost nothing about a user’s IRAF environment from the start except that they have the proper packages installed.
  2. Lack of Documentation: The documentation for SPECROAD is frankly inadequate. It was an in-house tool for the SAO, so the publically-available documentation consists mostly of one webpage describing what the scripts do. I have now written up both an installation guide (because there are a lot of pre-requisite pieces of code to install) and a E-SPECROAD user’s guide.
  3. No Installation Instructions: There were several IRAF packages to install (available here). The shell scripts required not only the installation of several IRAF packages and the compilation of several C programs, they used korn shell (ksh) which I was unfamiliar with. And, as I would also soon discover, the ksh installed on the Mac had serious bugs in its list handling. There is now a fairly compete installation guide laying out all the pre-requisites and addressing installations on both Macs and Linux boxes.
  4. Undocumented Bugs: The available SPECROAD scripts had major bugs whose workarounds were undocumented and only available when I would email someone at the SAO to inquire about them. In one case, you had to know to actually break out of the script with Control-C, then run some of the reduction in IRAF, and then restart the script! E-SPECROAD has been fairly extensively debugged. It’s not bug free, but the exterminator has made some serious passes at the code.
  5. Assumed Availability of Spectral Templates: The SPECROAD scripts typically relied on pre-set spectral line databases for different grating/central wavelength configurations instead of having the user exploit the IRAF identify command to build a database. E-SPECROAD is geared toward the user who is going to wavelength calibrate their observations by building the spectral line database for themselves.
  6. Assumed Use of Low Resolution Spectra: The SPECROAD scripts were mostly pre-configured for working with 270gpm gratings and required some tweaking for 600gpm. E-SPECROAD can work with either configuration without editing the code.
  7. Inconvienent Backups As Data Reduction Progresses: If one of the scripts executed by SPECROAD crashed, you had to dig around subdirectories to “backtrack” the changes before restarting the script. With disk space not an issue, I prefer monolithic backups of the entire data directory at certain key points in the data reduction pipeline. Since you may not like this form of backup (as they consume a lot of disk space), they are optional.

Today, I am posting E-SPECROAD online as a beta release along with installation instructions and a user’s guide. All the other external users of Hectospec I am aware of, all two of you, can enjoy or complain to me about this code. The ones I am unaware of are free to use the code as well.

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