As the successor of the popular Nikon D800 this even more sophisticated camera was introduced late July 2014. It has the same sensor with 36.3 Mp. But according to the press release of Nikon Corporation the D810 is the "first digital SLR camera in Nikon's history to offer a minimum standard sensitivity of ISO 64 at which superior clarity and image quality with rich tones is achieved"
Features are an electronic front-curtain shutter that prevents blur
in images with minimization of vibration resulting from the operation
of mechanisms with shooting. Highlight-weighted metering, with which
exposure values that reduce loss of detail in highlights (blown highlights)
are determined, convenient for capturing theater scenes and the like.
display zoom" function that displays enlarged views of two separate
areas of the frame side-by-side for checking level if the building
is aligned with the horizon with live view photography.
More technical details can be found here.
Early February 2015 Nikon introduced a very special version of the D810. The Nikon D810A is 'designed exclusively for astrophotography (..) and not recommended for general photography', as Nikon's press release is stating.
has the same features as the 'regular' Nikon D810 but it has no low-pass
filter, but an optical filter adopted to enable reproduction (4 times
greater than the D810) of vivid red images of nebulae and galaxies
that emit H-alpha light. When used in general photogrpahy all images
will have a red cast. The camera offers smooth and enjoyable shooting
with new functions specialized for astrophotography, like a long-exposure
manual (M*) mode that supports shutter speeds as slow as 900 s!!
Information necessary during shooting is displayed in the viewfinder
so that images can be framed without taking your eye off the subject.
In addition to shutter speed and aperture settings, a virtual horizon,
which is always illuminated in red when enabled, can be displayed
to help keep the camera level. Features like this allow the user to
focus on shooting.
See for technical details here.