Detecting solar reflections
You have a few problems to overcome. A telescope will improve sensitivity, but will also be susceptible to vibration, so that your light source will appear to be moving around at a rather fast rate.
Your light source will appear to be a point source (like a star). This means that all its light will fall onto one or more (adjacent) pixels of a sensor array. Vibration and sagging of the optical mount, along with the on/off nature of the source means that tracking is almost impossible.
You must discriminate between a very bright pixel(s) against a background average that can vary (as clouds pass by, or shadows appear/disappear).
One possible sensor that I've used before is an optical mouse element. It is a small array, but incorporates some registers that calculate for you some basic image statistics:adns-2620 data sheet
You can read registers via standard serial-port protocols.
One register gives the average pixel value
Another register gives the maximum pixel value
These are calculated for each frame collected. From these two values alone, you might be able to discriminate between "no signal" from "signal" without having to search for the exact pixel that's brightest.
Some slightly higher resolution, higher frame-rate versions are available (for gamers) that might give better results. An example low-resolution ADNS-2010 image, with mouse lens replaced with a longer focal-length lens:

It will be very difficult to improve upon the human eye, and the performance of this system will be markedly inferior.