That’s exactly why they are using commercial lenses! Canon’s modern AR coatings are so good that the performance for low-surface brightness imaging beats larger-aperture telescopes which can gather more light but scatter it around the image. See the third page of https://arxiv.org/abs/1401.5473

From the various links in the comments, the telescope uses special filters in front of the lenses to capture the faint glow in specific wavelengths emitted by the circumgalactic medium (a new word for me!) aka "gas" around galaxies.