FAST LIGHT COLLECTION
The 210mm parabolic primary mirror at the heart of the PN210 Mk II works at f/3.8. This is considered a fast focal ratio, a photographic term that essentially describes how quickly a certain depth of image can be delivered. One major benefit of a fast system is that exposure times can be kept relatively short. This also goes hand-in-hand with the excellent portability of the telescope. Transport it to a dark-sky location and even with moderately accurate polar alignment, it should be possible to take relatively short but still quite deep exposures.
The 800mm focal length of the primary mirror delivers a fairly wide field of view at prime focus. Using a Canon EOS 6D, a full frame DSLR, our images covered a sky area 2.5x1.5°. Consequently, the fast, wide-field delivery of the PN210’s optics makes it best suited for the imaging of extended deep-sky objects.
Being a Newtonian reflector, the PN210’s field does suffer from coma, which becomes very noticeable towards the edge of frame, especially when using a camera with a large sensor. A matching field flattener is recommended to reduce this issue.