I am not sure what a FIT file is, but in ArcScene you can control the quality of the raster as described in this blog. Remember that ArcScene loads everything into memory, so that larger rasters can cause other display and performance issues if the quality is raised. I recommend testing out different sizes and qualities to see what works best for you.
The process is still the same, follow the blog and adjust the look of the rasters in ArcScene. The procedure described in the blog are raster format independent.