Problem designing a beacon light circuit
LDRs have have an increased resistance at dark than when there is light reaching them,so you could use a transistor to make it turn on only when there isn't light.Connect a transistor to the supply with the LDR(with the base terminal) and the collector directly to the base of the T3 IRFP042.The emitter pin would go to the negative terminal of the battery.How this would work:When there is light,the LDR will lower its resistance,thus the base current will increase,allowing just enough current to pass in the collector pin to turn the IRFP042 off permanently.When it will be dark,the LDR resistance will increase just enough to deactivate the transistor and allow the IRFP to be switched on by the multivibrator.Use a beta suitable for saturating the transistor