FK61 glass made by CDGM in China usually has an Abbe Number of 81.6 − very similar to FPL-51. It is not the equivalent to FPL-53, which has an Abbe number of at least 94.94.
There are 150mm FPL-53 Triplets available today, like the Esprit and the TS Photoline, but they may not be price competitive with the AT152EDT (at this time). The TS150 has a Starlight 3.5" focuser, so that explains some of the differential in price. I would be willing to bet that there will be a FPL-53 150mm Triplet at a similiar price point by the time ths AT152EDT is ready for market. Competition is good.
There is also a Lanthanum element in there too. The combination works really well. I doubt you'll see anything at the same price point with the same correction.
The focuser is very good. I normally change out focusers for FT's but this one doesn't need it. It's 3.5" and very well made. Its all about the prescription the glass is only one factor.
Have you ever tried an AT111EDT? That's FPL-51 and a design by Thomas Back and shows how a well designed implementation can work.
Take a look on Astrobin for AT111EDT images.
Edited by Phil Cowell, 06 November 2017 - 10:45 AM.