Here is an example of an APO telescoope, made in the United States, with color crossings at different wavelengths, meaning 3 colors focus at exactly the same distance from the optics. No longitude CA.
A super APO has been described as having 4 color crossings, and there is not too many testing positive for this.
Jul 22, 2009 at 10:01 AM
Previous versions of JimBuchanan's message #7331451 « question about 'APO' lens »
