You can breadboard some Schmitt trigger oscillators using CMOS gates or 555 timers. But the best effects are pre-programmed sequences in an embedded uC sold with outside xmas lights.
**broken link removed**
98:02 This ratio at 30 - 50 Hz is very difficult to perceive. I think there is something missing or wage. Twinkling like stars may need different combination !!!
You need 30 - 50 Hz with 98% ON time and 2%OFF time.
Can this type of effect be perceived by normal human is the question.
This means that can one see this as twinkling?? It would look continuously glowing.
If you are familiar with micro controller use some small/basic uC like PIC10 series or PIC12 series. You can create random pulse at different freq which will give very good twinkle effect. This will give good look and attractive. u can re-prog it whenever u want to change the pattern.