Inc. Randy offers the Telekit as an antidote for aperture fever. The delivery time for the mirror will allow assembly of the hardware components of the scope. It accepts data on the optics, and calculates telescope performance parameters. Sometimes the secondary mirror size is subject to discretion, and he tends to advise planetary observers to install smaller secondaries, if they wish to minimize diffraction effects. Deep sky observers are steered toward larger secondaries to maximize field illumination at low power.
Secondary offset is a common topic of debate.
It is important for photography for symmetrical field illumination. The uneven field illumination which results from a centered secondary is not visually detectable, and collimation is easier with a centered secondary. Cost and difficulty in application rapidly rise with mirror size. Randy recommends enhanced coatings on the secondary and regular coatings on the primary as a most cost-effective solution. Some high-reflectivity coatings are prone to scatter, which can reduce visibility of low contrast detail.