SBIG Deep Space Spectrograph
Optimized for the ST-7XME or the low cost ST-402, it will also work well with ST-8/9/10/2000 cameras and ST-237s. It will not work with the STL series due to their deeper backfocus required by the built in filter wheel.
This item has been discontinued.
SBIG’s new Deep Space Spectrograph (DSS-7) is aspectrograph optimized for the types of spectral observations that an amateurhas always been interested in, from stellar classification to nebular analysisto galactic red shifts. It is amore general purpose instrument than our Self Guided Spectrograph (SGS), whichis optimized for stellar work, and is much less expensive. It is optimized for the ST-7XME or the low cost ST-402, and will workwell with ST-8/9/10/2000 cameras and ST-237s. It will not work with the STL series due to their deeper backfocusrequired by the built in filter wheel. Thismemo describes the DSS-7 in detail, and present examples of observations thatcan be made by the amateur.
DSS-7 attached to ST-7XME camera
Spectroscopy Fundamentals: a spectrograph is a device that can produce agraph of the intensity of light as a function of color, or wavelength. A spectrometer is a device that measures only one selectable color, and amonochromator is a device that transmits only one color. The DSS-7 spectrograph is designed to separate and focus wavelengths from4000 to 8000 angstroms across the width of an ST-7 CCD. The human eye is sensitive from about 4500 (deep blue) to 7000 (deep red)angstroms, with its peak sensitivity at 5550 angstroms. The silicon CCDs used in SBIGs cameras have a larger range of sensitivitythan the eye. Most stars put out acontinuum of wavelengths with a number of absorption lines superimposed on it. Most emission nebula like the Orion Nebula produce a spectrum this iscomposed of a few bright emission lines, such as H-alpha (a hydrogen line at6563 angstroms), H-beta (a hydrogen line at 4861 angstroms), and O-III (a triplyionized oxygen line at 5007 angstroms). Anangstrom is one ten billionth of a meter. Youwill also quite often see wavelengths written in nanometers, which is onebillionth of a meter. 6563angstroms (A) is 656.3 nanometers (nm). Galaxieshave a spectrum that is an aggregate of many stars, and have a similar spectrum. Most galaxies only have a few obvious features – the cores tend to showa sodium absorption line due to the older stars there. Seyfert galaxies and other active galaxies show an excess of H-alpha,which is great since it makes a red shift much easier to determine. Quasars, nova and supernova in general exhibit strong 6563 emission. In the case of quasars it can be red shifted quite a bit, hundreds ofangstroms, so it may actually appear at a different wavelength. For a nova, the line will only be shifted slightly since the star is inour own galaxy, but it may be greatly broadened. The individual hydrogen atoms are moving very fast due to the tremendoustemperatures involved, producing Doppler broadening that smears out the line.