obviously the frequency depends entirely on the value of the capacitor, and the duty cycle on the resistance.
with these values and the 12V relays I had I got about a 1HZ oscillator ... I didn't measure it with the stopwatch but I didn't have big claims!
The important thing was that it was as minimal as possible, personally I had also made a card with NE555 but after a few months, being out on the outside it went crazy, I had to change the integrated circuit because it no longer wobbled to stay out in the cold. hope this goes better for EXTREME conditions!