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To avoid vignetting of the dispersed beam by the LHIRES diagonal mirror I normally set the position of the spectrum approximately 1/3 from the bottom of the camera field. I see though that the manual says to move the mirror adjuster towards the slit door. This moves the spectrum towards the top of the field. Which is correct? (Directing the beam towards the slit door appears to be to the same side as the mirror which seems to me to be the wrong direction)

Robin