Ca II InfraRed Triplet

This page shows examples of what the Ca II infrared triplet lines look like when observed with the MCCD. The actual data is from a Kitt Peak atlas, smoothed to our resolution, so the exact width of the spectral range may not match.

First, as a reference, here is H-alpha, 6563 Angstroms. A Single is on the left; the spectral plot on the right.

Now, the three lines of the triplet are shown: 8498, 8542, and 8662 Angstroms. They look similar to H-alpha, and to each other, but the nearby lines always form a unique pattern that allows them to be identified.

The best line is 8542; next best is 8662. The 8498 line is weaker, narrower, and has more blends close to line center.

Setup reminders

• Use a red filter. We work in the first order of the grating, but the second order at 4249, 4271, 4331 will leak in without the filter.
• The MCCD is less sensitive at this wavelength. The ND filter may have to be completely removed, and longer exposures used.

Barry LaBonte

Last modified: Thu May 22 02:47:48 HST 2003