MOTM

is there anyone who could give a a quick schematic for an LFO that would
vary a 50% pulse rate between 0.5 Hz and 8 Hz? I have some easy
schematics using an LM555 (which is fine) but i'm having a big problem
finding the right resistor and capacitor values to satisfy the small
frequency range. Sorry for the OT, it's kinda related (i need something
to trigger the slide advance on the slide projector we use during our
show) thanks in advance. -nate