[Leo.G (Leo)]

I'm always seeing APO refractors for sale in the classifieds, these are mostly shorter focal lengths. I understand faster units (f ratio) for photography and wider field of view compared to comparative sized longer focal lengths but do longer focal length tubes have any strengths?


I don't have the luxury of owning an APO, champagne tastes on tap water income but I always keep an eye out just in case, one day.....
Do they make longer focal length APO's?


My original model Megrez 80mm is a semi APO, I've never figured that "semi" bit out and it has more much CA than my old 152mm x 1200mm Skywatcher which is an Achromat. Actually, the Skywatcher is stunning visually for my old eyes.
CA does show up in images though but not significant, nothing that can't be removed (or significantly reduced) in PhotoShop with the eye dropper used on RAW images.