Calibration of HST narrow band filters using the Orion Nebula.

Abstract

HST images in three emission line filters: Hα, [O III] and [N II] have been calibrated. The CCD sensitivity was determined by comparing regions within HST frames with the corresponding surface brightness determined from ground based Orion Nebula observations. Corrections for continuum within each filter were made. It was necessary to correct the [N II] image for an Hα contribution. The frame-to-frame dependence of CCD sensitivity was also determined.