555 - HIGH then long delay
General approach is to separate the discharge resistor into two using diodes. 







simulate this circuit &ndash; Schematic created using CircuitLab

The capacitor C2 charges through R1 + R3 and discharges through R2, ignoring diode drops and discharge transistor collector voltage when on. 

Approximately, on time is proportional to R1 + R3 and off time is proportional to R2, so you can make the ratio suit your application.