Having built an iStar Anastigmatic scope ( a 127mm f12 R30 TCR in photo below) I know how wonderful these long focal length objectives in R30 glass can be. iStar are now back in the business of producing these objectives, after having stopped for some time as founder Ales Krivanek had been ill. It's good to see a return of these objectives:
http://www.istar-optical.com/objective-lenses-ii.html
The 250 mm (9.8") F/20 R30 looks magnificent, and you'll never have to think about CA with a focal length of 5000mm! Wish I could afford it, and had the room in the observatory.