The big picture shows a normal photo through an f=1000mm F/9.8 telescope with a Canon 20D. The field of view should be around 1° 17‘ 20" according to this FOV calculator. The small frame is taken with an additional 2x Barlow lens between prime focus and the camera sensor. It ends up magnifying the image around 2.7- to 2.9-fold. I guess this could be tuned a little each way by inserting the Barlow differently in the focuser or with a T-ring standoff between the camera and the Barlow.
Something to try on the moon or bright planets once the skies are clear again...