I have always wondered about refractors for imaging.
It looks like results are worse if you take luminance.
It seems that you can only take RGB for the sharpest shots?
It seems also that Takahashi has a solution as discussed on another thread here.
http://www.iceinspace.com.au/forum/s....php?p=1138642
- a 5 element design:
http://www.astromart.com/classifieds...fied_id=870387
http://www.kyoei-tokyo.jp/shopdetail/000000006021/
cheers
Allan