How to update to Asynx Planetarium v2.50 ?

You can keep your old installation and just install a new version as long as they have different release numbers.
If you just like to use the new version then:

Deinstall your old program version and install the new:

1. Go to START->Settings->Control Panel->Add/Remove Programs.

2. Search for the old version and click the "Change/Remove" button.

3. Download and install Asynx Planetarium v2.20.

4. Your stored city/locations are not the same anymore in v2.20