... This page is intended to give the reader who is unfamiliar with the spectroscopy mode of GRIM enough basic information to be able to effectively plan observations, somewhere between a FAQ and the actual User Manual. ... A slit is placed in the optical path near the grism; otherwise, slitless spectroscopy can be done in the "objective prism" mode. ... Keep this in mind if you chose to dither the position of your object along the slit in order to make a master sky frame for calibration purposes. ...