SBIG Spectrograph Review

Contribution: Dale Mais

In 1999, Santa Barbara Instrument Group (SBIG) released a novel product, a spectrometer, into the amateur market place.

Click on picture for a larger version.

The spectrometer is designed to operate with the ST-7/8. The object that is to be analyzed is viewed on the tracking CCD, simultaneously with the slit. The slit is backlit by an LED during setup to render it clearly visible on the tracking CCD.
The object is manually maneuvered onto the slit using the telescope controls, and is held there using SELF GUIDING during a long exposure. The spectra is recorded by the imaging CCD, oriented long-ways so the spectra falls across 765 pixels, with a height of about 16 pixels for stellar sources.
Two gratings and two slits are available for maximum versatility.

The standard grating, 150 rulings per mm, gives a dispersion of 4.28 angstroms per pixel (476 Angstroms per mm), and allows the user to capture the entire interesting range from the calcium H and K lines to H-Alpha (3000 Angstroms) with a single exposure. Depending on the slit size, the resolution will be 10 or 38 angstroms per pixel.
An interchangeable high resolution grating can also be used that gives 1.06 angstrom per pixel (118 Angstroms per mm) dispersion, with a resolution of about 2.4 angstroms when used with the narrow slit.The spectral range is smaller, being only about 750 angstroms. This resolution is adequate to detect the Doppler shift due to the earth's motion around the sun when carefully calibrated, and detect spectroscopic binaries.

Features of the SBIG Self-Guiding Spectrometer:

Object analysed is viewed on tracking CCD simultaneously with slit (back illuminated)
Object is held on slit by self-guiding feature, slit = 18 microns
Spectra recorded on imaging CCD
Two gratings:	150 lines/mm <=> 4.3 A/pixel
	600 lines/mm <=> 1.07 A/pixel
Wavelength range:	~3800-7500 A (range in my experience 3600-10000A)
	~3200 A coverage in lo-resolution mode
	~750 A coverage in hi-resolution mode
Input window on bottom of unit for introducing calibration standards

Spectrometer attached to rear of C-14 via flip mirror

Several modifications to the spectrometer have been made which makes operation more convenient:

A motor has been added to the micrometer which is controlled from a console at my computer table. This idea came from Maurice Gavin, an amateur leader in the area of spectroscopy who lives in the UK.
The illumination slit likewise is controlled from the console.
A fiber optic lead feeds from two gas discharge tubes (Hg and H2) into the spectrometer which allows for the imprinting of wavelength standards onto the spectrum for calibration. These emission tubes are also controlled from the console.

Gas discharge tubes with fiber optic leads to spectrometer

See also the SBIG spectrograph review & test by Olivier Garde!

If you are interested in spectroscopy join the SBIG spectrometer user group.