ZWO FF90 f/6.8 APO REFRACTOR Dew heater longer focal lengths will magnify

longer focal lengths will magnify the image but

The adapter centres Baader's Fluorite Flatfield Converter

the backlash varies along different points of the worm drive and generally also increases overtime

CaF2 has got an impressive refractivity which enables construction of the ultimate lens system that can deliver an incredible amount of sharpness across a very broad spectral range

but as an OIII parallel filter to better remove stars from images

ZWO FF90 f/6.8 APO REFRACTOR Dew heater longer focal lengths will magnifyThe ZWO FF90 is an apochromatic quadruplet flat field astrograph that offers high performance for an exceptionally low price. The quadruplet design makes it perfect for both visual observation and astrophotography. The objective lens features an element of extra low dispersion glass (ED) that minimizes chromatic aberration. The ZWO FF90 is a versatile instrument and excels not just at imaging, but as a grab & go visual telescope. The OTA itself weighs