Nikon has launched a modified version of its D810 DSLR, the D810A. The D810A is the first full frame camera in the world optimized for astrophotography.
Most cameras have an IR cut filter that is designed to allow only those wavelengths of light that the human eye can see, so that the resulting image looks similar to what it looks to the human eye. However, the light emitted by far away stars and galaxies are often well beyond our visual range, and in order to capture them properly, you need a camera designed specifically for such application.
The D810A IR cut filter has been optimized to allow transmission of the hydrogen alpha spectral line, resulting in four times greater sensitivity of the 656nm wavelength. This lets you capture the red hues of diffuse nebulae and constellations in greater clarity. Due to the alterations to the filter, the D810A is unsuitable for regular photography, as anything other than pictures of the night sky will come out with a reddish hue. Due to this, the D810A is a very specific tool, for those who are very serious about astrophotography.
Nikon D810A (left) vs Nikon D810 (right)
Other than the IR filter, the D810A also lets you set shutter speed from 4 seconds, all the way to 900 seconds (15 minutes), along with the usual Bulb and Time settings. The ISO sensitivity has also been expanded from ISO 200 to 12,800 (expandable up to 51,200). There is also an electronic front curtain shutter mode, which uses the electronic front curtain on the sensor as the shutter instead of the mechanical shutter, as it helps reduce the minor camera shake that can occur with the mechanical shutter.
Other than that, the D810A is identical to the D810, including having the support for NIKKOR lens. You can also attach it to a telescope using lens adapters.
The Nikon D810A will be available in May 2015, with the pricing being announced later.