According to Nikon, they make a D810A which is dedicated to astrophotography. Curious to hear if anyone has one and whether or not it takes star images better than a D810.
https://www.nikonusa.com/en/nikon-products/product/dslr-cameras/d810a.html
https://www.nikonusa.com/en/nikon-products/product/dslr-cameras/d810a.html