2 Introduction to HDR Imaging High dynamic range (HDR) imaging is becoming a popular tool among professional photographers.  It is primarily used in outdoor scenes where the radiances cover a range that exceeds what can be captured in a single film or digital exposure.   The basic technique is to take a set of exposures, bracketing the range so that everything in the scene is properly exposed on at least one frame.  The frames are then computationally blended to obtain a high dynamic range image.  A tone mapping is performed to bring out the desired details for a given display or print.  Sophisticated tone mappings take into account the spatial variations of intensity across the image, mimicking the adaptation of the human eye to a high dynamic range scene. Astrophotography would seem to be a natural fit for this technique, since the objects we photograph cover an enormous range of brightnesses, ranging from the sun (magnitude -26) to faint nebulas and galaxies (magnitude 10 and beyond).  There are a number of difficulties however, many of which have been encountered and solved already by the CCD imaging community.  The concepts of stacking to reduce noise is the beginning of the process. This notebook illustrates some examples of HDR imaging for astronomical scenery.