Macalester College Physics and Astronomy Department:

Spectroscopic Binary Project

Our original project endeavored to determine the radial velocity of the binary star Algol using spectrum obtained using the Macalester telescope and spectrometer. We soon found that we were unable to obtain any stellar spectra with our equipment. This instantly reverted our project into calibrating the spectrometer so that it could be used for future projects.

The spectrometer consists of a set of mirrors, lenses, a diffraction reflector and a slit connected to a camera with two CCDs. Light spectrum is obtained in the following manner. Light enters through the slit in the front of the CCD rendering it into the image of a vertical line. The light reflects off a series of mirrors onto a diffraction reflector. The diffraction reflector breaks the light into a smooth continuum of wavelengths. This image is then reflected off another series of mirrors and onto the Imaging CCD. In order to align the star onto the slit, the Tracking CCD is used. The Tracking CCD gives an image of both the star and the slit allowing the observer to make slight movements in the telescope so that the star may fall onto the slit.

In a properly functioning spectrometer, once the Tracking CCD produces an image of the star on the slit, one should be able to obtain the spectrum of the star. We found that even after aligning the star onto the slit using the Tracking CCD we were unable to produce any spectrum. We concluded that there must be a misalignment in the spectrometer such that the Tracking CCD does not correctly reveal when the star is on the slit. Our objective now became to realign the spectrometer.

In order to calibrate the spectrometer we simulated a star using an incandescent light focused onto a pinhole covering the aperture of the spectrometer. We found that this method produces a star-like image on the Tracking CCD.

Spectrometer	Calibration	Results