| 摘要 |
The invention provides a spectrographic device 10 for astronomical spectroscopy, comprising an entrance slit 12 arranged to transmit a portion of a light beam received on the slit 12; a collimator 14 operable to collimate the portion of the beam transmitted through the slit 12; a dispersive element 16 configured to receive the collimated beam from the collimator 14 and to disperse the light; and a focuser 18 arranged to produce a focused image of the dispersed light. The focuser 18 is associated with a focus aid adapted to be insertable into the path of the dispersed light, preferably between the dispersive element 16 and the focuser 18, to thereby facilitate focusing of the device. The present device is particularly well suited for amateur-sized astronomical telescopes. The focus aid may comprise an image sharpener such as a slit mask. Alternatively the focus aid may comprise a Hartmann mask. The entrance slit 12 may be angled to the optical axis 20 of the device 10 to permit viewing of the slit 12 by way of light reflected by the slit 12.
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