Wavelength calibration

The procedure, which is critically dependent on the availability of certain arc lamps, depends on the bandpass of the order blocking filter. The narrowband filters are only rarely used; most observers use the intermediate band filters for high resolution work. The broadband filters are only used for the lowest resolution imaging or in regions not covered by the TTF filter set.

      Narrow band (~30A) filters  (rarely used)
      Intermediate band (~200A) filters  (high resolution work)
      Broad band (~1200A) filters (low resolution work)

Here is a really useful tip which will make a lot more sense to you once you get some experience with TTF calibration.  The only calibration method that you really need to master is the intermediate band case. The lambda-z relation you derive from the calibration cares nothing about the blocking filter. The choice of blocker is purely for convenience. Thus, if you need to use the R filter to isolate your line, simply calibrate with the TTF blocker closest to your wavelength region (i.e. B6, R0 or R1), and then switch the TTF blocker with the R filter before observing.

Here is a summary of the available TTF filters. You can download this figure from here.

Newsflash: Note there is presently no blocker between 420nm and 480nm. We can mimic something close to a suitable (but rather broad) blocker using a B filter in conjunction with the MITLL3. This was used successfully in Feb 00. See here for example profiles. Note that the peak transmission is about 80% or so. The lower value reflects the CCD q.e. It is advisable to use this option at the lowest resolutions, i.e. Zc=-3.