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If you are shooting astro and the coma is good, it could be a good lens. If you are shooting landscapes, 2.8 is more than enough. Hell, I have never shot a landscape wider than f4.
I am thinking slot canyons where tripods are a nuisance and f2.8 ISO 800 gets you 1/15th hand held. 1.4 would be nice
My major reservation is the likely tiny rotation from minimum focus to infinity