Radeburg is almost part of Dresden but, the Cranzahl line is quite a distance.
I'm not sure you could do it in a day without a car. Rail service connections are slow and infrequent for part of the distance and not oriented to easy trips from Dresden. There is another Narrow gauge at Zittau, connected to Dresden by direct trains every couple of hours, taking less than two hours.
That line splits at Bertsdorf and, the used to have multiple train action there.
Google "Zittauer Schmalspurbahn" pick the first listing and, click on the (oddly) New Zealand? flag. that gives you a full site in english with all the special events, schedule etc. If you search Oberelbische Dampfschiffe,
you will find the river steamers with schedule (Fahrplan) which says which
trips are by paddlesteamer (almost all).
LS
