First let me apologize to Alun and others for any confusion my post of the
formula to calculate the freqency. As it turns out the formula is incorrect.
When I did the calculation I got a negative number. I knew that could not be
right so I ignored the - sign.
I did some checking and find...
Audioguru is correct, I was having a brain cramp. Increasing the value of the
base resistor(39k) will decrease the flash rate.
The 2ln term actually means 2 times the natural log of the result of the RC calculation.
The circuit and formula is from my notes.
I calculate the flash rate to be 2.012 Hz.
The attached image and formula was used to calculate the flash rate.
Reducing the value of the 10uF capacitor and increasing the value of the 39k
resistor will increase the flash rate.