Istar Optical is now making visual APO objective : no OTA for the moment.
It follows series of recent designs.
The second series of designs are smaller and follows the lanthanum glass used to match ED/SD/fluorite use.
The one that is well known was a 125mm Stellarvue/TS Optics/... and a new is a Takahashi Caf2 + lanthanum 100mm FC-100DZ
So Istar Optical is launching a new serie with the 160/1200 as the leading design
Spots of the lenses are now visible on the site so no break of my confidentiality agreement with Mr Krivanek to show it to you.
As it is a doublet, the best focii for Deep Sky use and Planetary use can be different : that works !
a) Deep Sky : from Hbeta, OIII going to Halpha you have a balanced spot size for photography and visual use. (predicted better that the previous APM due to high end glass combination)
b) Planetary : I retro-engineered with Mr Krivanek information. I am glad to say that shifting the focus this is textbook sharp for yellow and orange (573-589nm), good extending to green and red. (546 - 614nm)
The best I can say is that I exchanged with him recently and the explainations he gave are clear : compatible with the modern refractor design that G.Düring and M.Riccardi hold for the APM refractors.
So using Fluorite and a lanthanum glass that has properties similar to the "Kurz flint" at a higher level, this one is "one step further".
I hope we could test it, a friend is negociating about this. Maybe we could call it, as a joke, to be named baby APQ.
As you can see : not a recent idea from Mr Krivanek
Disclaimer as usual : no common interest with Istar Optical.