I only know of the 3 inch Paracorr.
Any 3 inch Barlow lenses made?
Posted 06 October 2018 - 06:57 AM
No market for such IMO as most 3" eyepieces are long F/L used for low magnification in observatory class OTA's.
Posted 06 October 2018 - 08:09 AM
If you actually want one, you'll probably want/need to contact Harry Siebert: http://www.siebertop...80mm 4 eyepiece the relevant part is near the bottom of that page. I'm betting they are a low-volume product and he makes them as they are ordered so I'd expect a bit of a wait.
He'll even make 4" if you need it. He also makes some really long focal length eyepieces and such.
Posted 06 October 2018 - 08:10 AM
That does indeed go against the philosophy of 3-inch provision for visual use... which is the intent to avail VERY long EFL eyepieces.
But... one could easily Make giant Barlow be fitting good negative achromat to a tube... Tom