Wanted: Simple Light Detector Circuit

The basic photo diode amplifier is shown on page 6 of this opamp reference:

If you connect a second opamp as a comparator you can drive a small piezo buzzer directly from the second opamp. Since opamps amplify the difference between their two inputs, you connect the output of the first amplifier to one of the second one's inputs and connect the other input to a trim pot connected as a supply voltage divider that can produce any voltage between the positive and negative supply rails. I think I would start with a pair of 9 volt batteries connected in series as the supply, (18 volts total) with the junction between them as the signal ground. An LM358 dual opamp might be good enough and is very common.

Here are the data sheets for some photo diodes sold through Digikey.

Here is an example of a piezo buzzer that an opamp can drive:

You may need an additional lens to form an image of the star on the detector like your eye's lens does for your retina.

I need a sensitive light detector that i can place in front of the eyepiece of a binocular. This detector should sound a "beep" whenever it detects light. I would also like it to be powered by 6 vdc or less.