Askar 151PHQ 151mm f/7 Quadruplet Flat-Field Refractor

  151PHQ is a long-focal-ratio, flatfield astrograph newly launched after 130PHQ and also the biggest refractor of Sharpstar products till now. Instead of buying extra flatteners, calculating the backfocus of the flattener, or making a tedious connection to match the distance, astrophotographers can simply equip it with any possible imaging devices, make the target stay at the focus, and then the whole optical system is perfect for imaging.   151PHQ has a focal ratio of f/7 and a focal length of 1057mm. The aperture is 151mm, which is the largest of Askar refractors so far. The quadruplet lens with two ED glasses offers excellent control of chromatic and other aberrations. With its self-flattening design, 151PHQ offers strong advantages in the astronomical shooting. It supports a medium frame 60mm image circle, has a fine spot diagram with tiny distortion of the peripheral stars, and its central RMS radius is less than 2 microns.   151PHQ comes with a telescopic lens hood, a high-quali