Actually the FOA60, without the Q, is superior also. I find this fascinating. It is optically superior to a FC100 and to a TSA120.
Tom, no disputing that the FOA represents a phenomenal achievement by Takahashi for fluorite doublet optics, but it still will not "best" the equally well figured and executed triplet designs in the TOA and TSA lines. Its simple physics. I will let Takahashi's own literature on the TOA and TSA lenses speak for itself:
"The TSA design reduces color aberration to 1/3 that of fluorite apochromats."
"The Strehl ratio of a telescope is a numerical value that represents the percentage of the light of a star's image that actually falls into the Airy disk, compared to the theoretical maximum possible. A Strehl ratio of 0.95 is within 95% of perfection and is generally considered excellent. It equates to a 1/8th wave system accuracy. A Strehl ratio of 0.978 equates to a 1/12th wave accuracy. The Strehl ratio of the Takahashi triplet design is 0.992. This means that the Takahashi TOA and TSA objectives are within 99.2% of perfection. This compares with a Strehl ratio of 0.946 for a best-selling fluorite doublet system that has long been considered one of the very best telescopes available." [This quote predates the FOA which has a similar Strehl ratio to the TOA/TSA]
"The Takahashi triplets reduce the residual deviation from a flat line response over the blue to green portion of the visible spectrum of previous apo designs (even fluorite systems) by a third. The maximum deviation from all colors coming to a focus in precisely the same plane is no more than +/- 0.01mm from the blue end of the spectrum (436nm) to the H-alpha line at 656nm. The violet halo of chromatic aberration vanishes, and the tiny residual blue halation around bright stars at high powers essentially disappears. Stellar images are tight, with stars in the 12~20µm range, even at the very edges of the fully-illuminated image circle. CCD images are crisp and realistic, and visual observing is unparalleled in its clarity. Quite simply put, the Takahashi TOA and TSA optics have no equal."
Edited by NC Startrekker, 23 February 2021 - 01:15 PM.