Which brands produce "true" Apochromatic Refractors?
Disclaimer: I used to be a 99.9% astroimaging dude for the past decade and consequently have limited experience as an astrovisual dude.
My eyes (I switch between eyes when observing) couldn't see evidence of CA on Jupiter nor Saturn (and some doubles+DSOs) over the past few weeks of careful and regular observations. Both planets are currently ideally positioned near zenith after sunset, allowing me to push magnification as hard as my eyes allow for with my 105mm f/6 oil spaced triplet, if only for the fun of doing so. Still no colour, and even at 500x (2.5mm Toe with 2x TV barlow) near zenith, the 5 brightest moons of Saturn were still obvious at this magnification, as was the Cassini division. Please note that currently my favourite magnification with this small refractor is 126x (with 5mm Delite).
Drawing from my imaging experience with this f/6 triplet there is a very slight focus shift between green/blue and red filters, but it is an order of magnitude smaller than with my previously owned and cherished 102mm ED f/7 doublet from a popular and affordable manufacturer.
Given my observations with this telescope from the past 4 years, and putting textbook definitions aside, to my eyes and to my camera, at this stage in my journey, I consider my 4" f/6 CFF to be a true APO.
Edited by Suavi, 16 October 2020 - 05:26 PM.