Check on JPL DE405 using modern optical observations

JPL DE405 is compared with optical positions of the outer planets Jupiter to Pluto. Systematic errors in some of the optical observations complicate the interpretation of the residuals between observation and DE405. A common offset in the right ascension of the outer planets suggests a frame-tie problem between DE405 and the ICRF. It is concluded that the overall accuracy of DE405 is better than 50 mas for these planets in the period 1984-1997.