Spectrographe DPSM

Double Passage Soustractif Multicanal

Multichannel Subtractive Double Pass

MSDP image in H alpha (Meudon, 7 monochromatic channels after computation) - cliquer sur l'image (187 K octets)

The MSDP system is a 2D imaging spectrograph, which allows to observe a 2D field of view in several simultaneous channels (typically 9 to 30 simultaneous wavelengths in the line profile). Inside each channel, the wavelength varies linearly along the direction of dispersion. Between two contiguous channels, there exists a translation of the wavelength of about 0.25 A (in H alpha).

MSDP spectrographs operate at:

• The Meudon Solar Tower (a 60 cm vertical telescope with a coelostat and a 14 m focal length spectrograph). The dectector is a 70 mm movie camera; the seeing is rather good due to the forest of Meudon (about 1"). The number of channels is 9 and the field about 1' x 8'. Time resolution is a few seconds. H alpha line and CaII infrared lines are currently used.
• The Turret Dome at Pic du Midi Observatory (2870 m). This is a 50 cm refractor (polarization free) with a 8 m focal length spectrograph. The detector is a 70 mm movie camera; the seeing is currently 0.5" and reaches sometimes 0.25" (the diffraction limit). The resolution of MSDP frames is nevertheless 0.5", because exposures times are long (100 ms); it would be better with a CCD. The number of channels is 11 and the field about 30" x 4'. Time resolution is a few seconds. H alpha and Na D lines are currently observed.
• The Vacuum Tower Telescope operated by the Kippenheuer Institut at the Teide Observatory (Tenerife, 2400 m). This is a 60 cm vertical telescope with a coelostat and a 15 m focal length spectrograph. The dectector is a 1000 x 1000 CCD camera (12 bits) and two lines can be observed simultaneously, as H alpha and CaII infrared line; the seeing is currently better than 0.5"; the time exposure is short (10 ms). 10 channels are available, and the field is 15" x 2'. Time resolution is 11 seconds.
• The Coronograph of the Wroclaw Astronomical Institute (a 50 cm objective with a 8 m focal length spectrograph). The dectector is a 600 x 600 CCD video recordr (S-VHS). A 8 bit frame grabber allows numerical analysis. The seeing is about 0.5". The number of channels is 9 and the field about 40" x 5.5'.
• A new MSDP system will operate on the polarization free telescope THEMIS at the Teide Observatory (2370 m). THEMIS is a 90 cm telescope allowing circular and linear analysis of the polarization of light. A tilting mirror (active optics) will be available. The MSDP spectrograph will provide 30 simultaneous channels in various lines. THEMIS will offer 20 CCD cameras (300 x 400) for simultaneous observations of several lines in different states of polarization (Stokes parameters).

Some examples of results

MSDP intensity in H alpha centre of an arch filament system (VTT, Tenerife) - cliquer sur l'image

MSDP radial velocity in H alpha centre of an arch filament system (VTT, Tenerife) - cliquer sur l'image

MSDP intensity in H alpha wings of an arch filament system (VTT, Tenerife) - cliquer sur l'image

MSDP radial velocity in H alpha wings of an arch filament system (VTT, Tenerife) - cliquer sur l'image

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