Ages for Globular Clusters in the Outer Galactic Halo: The Second-Parameter Clusters Palomar 3, Palomar 4, and Eridanus**Based on observations made with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555.

We have used the Wide Field Planetary Camera 2 on the Hubble Space Telescope to obtain photometry of the outer halo globular clusters Palomar 3, Palomar 4, and Eridanus. These three are classic examples of the "second-parameter" anomaly because of their red horizontal-branch morphologies in combination with their low-to-intermediate metallicities. Our color-magnitude diagrams (CMDs) inV,V - I reach Vlim ≃ 27.0, clearly delineating the subgiant …