555 trigger point

Hi

I am wiring a 555 timer as monostable and I know when the trigger is grounded this strarts the monostable timing. I want to know at what point for the 555 the trigger is counted as being LOW and also what point is it HIGH, if my supply voltage is 9v will this point be half which is 4.5v which is what I would like it to be. The trigger will be coming from ldr/variable resistor potiential divider as seen in diagram.
If not can somone suggest a device trggered by about half supply voltage.

Thank you for any replies

When the voltage on pin 2 drops to or near 1/3Vcc(9V/3)=3V When the capacitor on pins 6&7 charges to 2/3Vcc or 6V the output on pin 3 will go back to near ground. When the 555 is triggered by the voltage on pin 2 the output(pin3) goes high, near Vcc.

hi e44
Extract from datasheet.

thanks for the replies, so trigger piont is about a third of power supply, thants ok because I can just get the values right for my ldr and vvvariable resistor so the midpoint is about 3v. Thanks for information

e44-72 said:

thanks for the replies, so trigger piont is about a third of power supply, thants ok because I can just get the values right for my ldr and vvvariable resistor so the midpoint is about 3v. Thanks for information

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Just remember that the voltage on pin 2 has to go back above Vcc/3 before the monostable times out, or the output will stay high until it does.