A binocular that offers great optics by day should be a great binocular for astronomy at night. Right? A binocular that kicks butt for astronomy should be a great choice for day work. Right? Not necessarily. The two applications certainly overlap, but I have seen many a great birding binocular come up short at night in terms of image brightness and optical correction, especially for flare and coma. Likewise, I have seen some high end astronomy binoculars that didn't have enough color correction to satisfy me for birding. You can tweak optics for a specific application, but doesn't mean it will be tweaked perfectly for all applications. There are, of course, some that work great both ways. I loved the way I could use a Nikon 10x42 Premier SE porro any time, day or night.