Subject: At what point does condensation occur

What is the most energy efficient way (least wasteful) of preventing 
condensation on machinery in my unheated workshop? Should I heat the 
workshop and by how much? Alternatively, should I buy a dehumidifier and 
reduce the relative humidity? If so, by how much to prevent condensation?  

I recently observed the following situation:

Ambient temperature(C)			13	
Machinery surface temperature(C)	3
Relative humidity			100% (it was raining all day)

The result was condensation on the machinery! However, what if the 
situation was as follows:

Ambient temperature(C)			13
Machinery surface temperature(C)	3
Relative humidity			50%

Would this situation cause condensation on the machinery?

On superficial inspection, I would say that since the temperatures are the 
same and the air is less saturated, condensation would not occur. However, 
what about the boundary conditions where the air meets the surfaces of the 
machines? Would the machine cool the air immediately in contact with it, 
thereby increasing the relative humidity and increasing the likelihood of 
condensation?

Finally, is there a relationship between the ambient temperature, the 
machines surface temperature and the relative humidity?

Re: At what point does condensation occur