Nikon Binocular for Astronomy and Nature Watch?

For bird watching, i use 8x21 binoculars. For astronomy, i use 8x21 Nikon binocular, despite the availability of 8x42 and 10x50.

For me, 8x21 Nikon binocular have these features: They fit in my pocket. Especially in winter, when i've got one of those huge winter coats, 8x21 nikon binocular can be parked in a coat pocket, so i always have them. They're light weight, so i can hold them longer. I find that 8x is not so powerful that i can't hold them steady. I find 10x to be very difficult to hand hold, and need a tripod (which i have). YMMV. For day time use, 8x and 21 mm is plenty of power and light. And, i have a 22x60 spotting scope on a very sturdy tripod if i need more. At night, i use my 8x21 binoculars to find objects that just aren't visible naked eye. I have enough field of view to navigate, and i get two magnitudes of dimmer objects than naked eye, allowing me to see many more field stars. And, when i want more light and power, i have a 240x254 monocular (10" telescope).

If you're going to have a tripod, and i mean a really good sturdy tripod, then go with larger binoculars.

But i went with really cheap binoculars this last time around. $25 at a sporting goods store. They're more fragile than expensive binoculars. But if you treat them like glass artwork, they'll last decades. Cheap binoculars may not have very good close focus. That matters if you want to do butterfly watching. I've never seen it as a problem for bird watching. And for astronomy, close focus is, by definition, irrelevant.

While i have binoculars and a spotting scope on a tripod, i find them quite awkward for astronomy. In astronomy the best views are straight up, so you're looking through the least amount of atmosphere. But straight through binoculars require that you get your head directly beneath the eyepiece for that. So binoculars with a 45 degree or 90 degree bend are better. If you can lie down on your back and hold them steady, straight through binoculars are fine. And i use them that way when otherwise doing a meteor watch.