The attached discrete 555 timer circuit does not result in the calculated times for hi and low periods.The time hi is slightly longer than calculated and the time low is off by quite a bit. (long)
I replaced the discharge transistor with a "virtual" device with no junction capacitance and the time low did decrease.However, it is still much longer than calculated.
I've noticed this type of problem too and to be honest, this is one of the situations where circuit simulation cannot make a substitute for bench and lab work.
One thing that you can do to get more accurate results is to reduce the time step. To do this, you should:
Hoped that helped. There is no hard rule to get accurate simulation results. The settings depend very much on the nature of your circuit as well.