The double-blind rules on page 189 distinguish between "clear line of sight" (not blocked by hills, woods/smoke, etc as per standard Total Warfare rules) and "visual range" (within a certain distance based on unit type and current environmental conditions). I am asking if a unit with a clear line of sight to a target, but outside of its visual range of the target, can declare and execute attacks on said target as long as some other allied unit has visually spotted said target (as implied by the wording on page 192).
Example:
We are playing using the Double Blind rules. The environmental conditions are Heavy Rain, limiting visual range for mechs to 15 hexes. I have an Awesome that wishes to make a PPC attack on an Atlas 18 hexes away. The Awesome has a clear line of sight under standard rules, but is outside its visual range of the target. I also have a Spider with a clear line of sight to the Atlas, at a range of only 6 hexes (and therefore within visual range, hence why I can see the Atlas under double-blind rules). Can the Awesome make an attack on the Atlas?