I'm running it over https on Ubuntu...

<IfModule mod_ssl.c>
<VirtualHost _default_:443>
  DocumentRoot /opt/observium/html/
  ServerName  observium.example.org
  CustomLog /opt/observium/logs/access_log combined
  ErrorLog /opt/observium/logs/error_log
  <Directory "/opt/observium/html/">
    AllowOverride All
    Options FollowSymLinks MultiViews
  </Directory>

        SSLEngine on

        SSLCertificateFile    /etc/ssl/certs/observium.example.org.crt
        SSLCertificateKeyFile /etc/ssl/private/observium.example.org.key

        <FilesMatch "\.(cgi|shtml|phtml|php)$">
                SSLOptions +StdEnvVars
        </FilesMatch>
        <Directory /usr/lib/cgi-bin>
                SSLOptions +StdEnvVars
        </Directory>

        BrowserMatch "MSIE [2-6]" \
                nokeepalive ssl-unclean-shutdown \
                downgrade-1.0 force-response-1.0
        BrowserMatch "MSIE [17-9]" ssl-unclean-shutdown

</VirtualHost>
</IfModule>