In astrophotography, these qualities are most desirable when taking pictures of nearby large objects, such as nebulae.
However, since the telecompressor increases the field of view, there could be vignetting in the image, depending on the sizes of the secondary mirror and the telescope tube.
[4] For a catadioptric system that has a combination of mirror and lens, the determination of reduction is more complicated, due to the fact that the telescope has a variable focal length, where the imaging plane can move along the axis of the imaging system.
The technology of the time used relatively small sensor sizes, so lenses designed for 35 mm film could not be used with their native field of view without additional optics used.
One effect of a telecompressor is that it reduces the diameter of the image circle, which means that a lens meant for a larger format can be used on a smaller sensor with a higher crop factor.