diff --git a/tap/src/main/java/ca/nrc/cadc/sample/RubinFormatFactory.java b/tap/src/main/java/ca/nrc/cadc/sample/RubinFormatFactory.java
new file mode 100644
index 0000000..b5d80d6
--- /dev/null
+++ b/tap/src/main/java/ca/nrc/cadc/sample/RubinFormatFactory.java
@@ -0,0 +1,33 @@
+package ca.nrc.cadc.sample;
+
+import ca.nrc.cadc.dali.util.Format;
+import ca.nrc.cadc.tap.TapSelectItem;
+import ca.nrc.cadc.tap.writer.format.PostgreSQLFormatFactory;
+import org.apache.log4j.Logger;
+
+import ca.nrc.cadc.sample.RubinURLFormat;
+
+
+public class RubinFormatFactory extends PostgreSQLFormatFactory {
+
+    private static Logger log = Logger.getLogger(RubinFormatFactory.class);
+
+    public RubinFormatFactory() {
+    	super();
+    }
+
+    @Override
+    public Format<Object> getClobFormat(TapSelectItem columnDesc) {
+        // function with CLOB argument
+        if (columnDesc != null) {
+            // oga.ObsCore
+            if ("oga.ObsCore".equalsIgnoreCase(columnDesc.tableName)) {
+                if ("access_url".equalsIgnoreCase(columnDesc.getColumnName())) {
+                    return new RubinURLFormat();
+                }
+            }
+        }
+
+        return super.getClobFormat(columnDesc);
+    }
+}
diff --git a/tap/src/main/java/ca/nrc/cadc/sample/RubinURLFormat.java b/tap/src/main/java/ca/nrc/cadc/sample/RubinURLFormat.java
new file mode 100644
index 0000000..85c985b
--- /dev/null
+++ b/tap/src/main/java/ca/nrc/cadc/sample/RubinURLFormat.java
@@ -0,0 +1,43 @@
+package ca.nrc.cadc.sample;
+
+import java.net.MalformedURLException;
+import java.net.URL;
+
+import ca.nrc.cadc.dali.util.Format;
+import org.apache.log4j.Logger;
+
+
+public class RubinURLFormat implements Format<Object> {
+
+    private static Logger log = Logger.getLogger(RubinURLFormat.class);
+
+    private static final String BASE_URL = System.getProperty("base_url");
+
+    public RubinURLFormat() {
+        super();
+    }
+
+    @Override
+    public Object parse(String s) {
+        throw new UnsupportedOperationException("TAP Formats cannot parse strings.");
+    }
+
+    @Override
+    public String format(Object o) {
+        if (o == null) {
+            return "";
+        }
+
+	String s = (String) o;
+
+	try {
+            URL orig = new URL((String) o);
+	    URL base_url = new URL(BASE_URL);
+	    URL rewritten = new URL(orig.getProtocol(), base_url.getHost(), orig.getFile());
+
+	    return rewritten.toExternalForm();
+	} catch (MalformedURLException ex) {
+            throw new RuntimeException("BUG: Failed to rewrite URL: " + s, ex);
+        }
+    }
+}
diff --git a/tap/src/main/resources/PluginFactory.properties b/tap/src/main/resources/PluginFactory.properties
index 56e18f5..9251e69 100644
--- a/tap/src/main/resources/PluginFactory.properties
+++ b/tap/src/main/resources/PluginFactory.properties
@@ -12,10 +12,10 @@ ca.nrc.cadc.tap.MaxRecValidator.impl = ca.nrc.cadc.sample.MaxRecValidatorImpl
 
 ca.nrc.cadc.tap.db.DatabaseDataType=ca.nrc.cadc.tap.pg.PostgresDataTypeMapper
 
+ca.nrc.cadc.tap.writer.format.FormatFactory = ca.nrc.cadc.sample.RubinFormatFactory
+
 ca.nrc.cadc.tap.UploadManager = ca.nrc.cadc.sample.RubinUploadManagerImpl
 
 #ca.nrc.cadc.tap.TableWriter = ca.nrc.cadc.tap.DefaultTableWriter
 
-ca.nrc.cadc.tap.writer.format.FormatFactory = ca.nrc.cadc.tap.writer.format.PostgreSQLFormatFactory
-
 ca.nrc.cadc.tap.ResultStore = ca.nrc.cadc.sample.ResultStoreImpl