Migrating nodes to entities

Ok thanks seem to have got it working using the following, not sure if my method is the best but it works. Sure there's probably a cleaner way of doing it.

class TicketCountMigrate extends Migration {
  public function __construct() {
    parent::__construct(MigrateGroup::getInstance('TicketCount'));

    // Select fields from the Drupal 6 node ticket count table. 
    $query = Database::getConnection('default', 'legacy')
                        ->select('node', 'n');
     $query->innerJoin('node_revisions', 'nr', 'n.vid=nr.vid');
     $query->leftJoin('content_type_ticket_count', 'f', 'n.vid=f.vid');                    
     $query->fields('n', array('nid','vid','changed'));
     $query->fields('f', array('field_count_plug_value'));
     $query->condition('n.type', 'ticket_count');
     $query->orderBy('changed');


    // Set source and destination.
    $this->source = new MigrateSourceSQL($query);
    $this->destination = new MigrateDestinationEntityAPI(
      'ticket_count',  // Entity type
      'ticket_count'   // bundle
    );
    // Set up database maping.
    $this->map = new MigrateSQLMap($this->machineName,
      array(
        'nid' => array(
          'type' => 'int',
          'unsigned' => TRUE,
          'not null' => TRUE,
          'description' => 'D6 Unique Node ID',
          'alias' => 'n',
        )
      ),
      MigrateDestinationNode::getKeySchema()
    );
    
    $this->addFieldMapping('field_count_plug_book', 'field_count_plug_value');
    
  }
}