HDR (High Dynamic Range Imaging) is according to Wikipedia:
In image processing, computer graphics, and photography, high dynamic range imaging (HDRI or just HDR) is a set of techniques that allows a greater dynamic range of exposures (the range of values between light and dark areas) than normal digital imaging techniques. The intention of HDRI is to accurately represent the wide range of intensity levels found in real scenes ranging from direct sunlight to shadows.This is a technique that I have not tried properly, and when I now had four exposures of the full moon taken the other day, I found that I might at least try. Photoshop CS3 is supposed to do it by itself, but result was not great - it lost all background information, although the moon was good.
I next tried the Program Photomatrix 3.1, purpose-built just for making HDR that can be further processed in other programs. After a few stumbling blocks, it worked fairly well as a first try. I lost some details in the moon, but the evening sky survived very well. It was post processed in PS CS3.
A little more try and fail and I might get it.