Photometry of Stretched Stellar Images from Observations of Space Debris

A photometric method is presented to derive the magnitudes of stretched images of background stars from observations of space debris.The basic principle of this method is described.An iterative approach is introduced to obtain segments of the observed image, with each iteration severing a segment of image from the previous iteration further into two segments, where the pixel values are above and below a threshold, respectively(-threshold segmentation).The set of segments usually contains a sufficient amount of connected areas corresponding to the stretched image regions of background stars, so that these areas can be selected out based on their pixel values to yield the detection of stars.Magnitudes of stars can be calculated from these connected areas.The error of this algorithm is approximately 0.02 mag, according to the comparison to the photometry with the IRAF(Image Reduction and Analysis Facility).