I have the Canon 6D, which is great for astro-landscape. It has flawless performance at ISO 1600, and a reasonable amount of noise at ISO 6400, easily fixable. The Samyang series of manual focus lenses are particularly well suited for astro-landscape due to their relatively low level of coma when compared with brand name lenses at the same wide apertures. Lots of APS-C shooters use the Samyang 8mm f/3.5 fisheye and lots of FF shooters use the Samyang 14mm f/2.8, both filling their respective frames. The 14mm is more-or-less rectilinear; I usually shoot at f/3.5 to f/4 for best sharpness and no coma. If you want a good astro-landscape lens that also has AF, you could use the Sigma 35mm f/1.4, with mild FF corner coma at f/2.0, zip coma at f/2.8. It is a fine lens, and note that its coma is less obvious than the Canon L 1.4. If you already have my dream landscape lens the Zeiss Distagon 21mm f/2.8, that works very well at f/2.8. All the legacy MF film era lenses I have around 50-60mm have significant coma at f/1.4 to f/2.8, and the best of the lot I have is the Nikkor 50mm f/1.2 AIS at f/4, still a little extreme corner coma (not objectionable, unlike the huge wings at f/1.2), but really sharp. (I like fooling around with the lens at f/1.2 for usual photography).You will have to ask around for info on modern 50-60mm lenses, which are more likely to be better corrected for coma. Jerry Lodriguess recommends the Plastic Fantastic/ Nifty Fifty Canon 50mm f/1.8 II ($125.00), and has a list of useful lenses on his web site. A good lens resource for coma information is the Lenstip review site.
If you want a dual-use astro-landscape and through-telescope camera, there are some compromises to be made. 95% of astronomers using DSLRs purchased to use with telescopes will have Canons, largely due to a hugely popular free computer program, Backyard EOS, that automates taking of subs, darks, biases, flats, etc., and also due to the large number of used Rebels out there which can be had very cheaply and adapted to full-spectrum/ hydrogen III sensitive by replacing the IR cut filter over the sensor (costs about $300.00 from most services). The noise issue for astronomers is best dealt with by taking large numbers of subs (the scene) and darks (lens cap on, camera at same ambient temp and same time as was used for the subs) and using computational means to eliminate random noise and bad pixels.
