As an SGL telescope approaches the SGL focal region, it will need to locate the projected image of the target solar system, starting with its host star.
At first, the host star is just one of the many stars in the sky, as seen from the SGL probe.
As the SGL probe approaches the imaginary line that connects the host star with our Sun and extends beyond, the host star will appear closer and closer to the Sun. Eventually, a secondary image will also emerge from behind the Sun, as it is shown in this simulation video:
The two images also get hundreds of times brighter at this time, as a result of the light amplification of the SGL.
When both images are visible, the probe is still thousands of kilometers from that imaginary line, the "optical axis", and needs to get closer. It can be guided in this process by the host star light. As the probe gets closer and closer to its target, the images of the host star not only brighten but also stretch into arcs; these arcs eventually form a full circle, the Einstein ring, as shown in this second animation (done with much reduced brightness levels compared to the first):
When the Einstein ring is full and uniform, we know that the SGL probe is within a hundred kilometers or so of the center of the host star image. Its search for the much fainter projected image of the exoplanet can now begin.