Umax do not list the Astra 5650 on their support website so no drivers are available.
You may want to try VueScan software instead, which installs it's own generic driver for USB scanners: http://www.hamrick.com
Test your scanner with the free trial of VueScan. if it works, you can then decide either to buy a serial number ($40) to register the trial version, or buy a new scanner instead.
As most new scanners now are only available as a multi-function device combined with a printer, it will cost you more than $40 to buy a good one of those.