Do you have to be an expert in a specialized field to be a good technical translator?

Well, this question seems like it is asked to many technical writers and technical translators but it is actually a misconception about technical authors. According to Jody Byrne in her book on Usability Strategies for Technical Documentation, being a technical writer simply requires having a basic knowledge on principles and technologies related to the products they are writing documentation for. There are certain skill sets however, that are important for a translator to possess in order to have a successful translating career. They are as follows:

• subject knowledge
• writing skills
• research skills

Subject knowledge means having a basic understanding about the technology and further information from an SME (Subject Matter Expert). 

Writing skills are something that every technical translator should try to master in order to effectively change sentences and words from one language to another effectively.

Good research skills are imperative for a translator as well as for any technical writer because they allow the writer to find the information that they may be lacking more easily and in a time efficient manner.

Byrne, Jodi. 2006. Technical Translation Usability Strategies for Translating Technical Documentation. Retrieved from 
http://books.google.com/books?hl=en&lr=&id=GJlyr3jqjvQC&oi=fnd&pg=PR9&dq=translating+technical+documents&ots=m_gODxIKCo&sig=GhBkexYARH27kc8YRGdN9G8IpRk#v=onepage&q=translating%20technical%20documents&f=false