As a builder of an iStar refractor, I still look in at their website now and then. They are one of the few objective builders left for potential scope builders to go to for quality optics. They offer APO, R30 Antiastigmatic, and Achromat products in large diametre, adjustable cells. Some of these Achro objectives, at the longer focal lengths, like f15, have no CA to be concerned about. The 220mm diametre f15 objective, for $3400 USD, seems like a bargain, provided you have the swing room to host a 3300mm focal length scope. Weight won't be a concern at 6.14kg for the cell. Link is here:
https://www.istar-optical.com/achromatic.html
For those who remember my iStar build thread, it's still here in the archives if your interested, and good with Advanced Search.
Have fun.
