[AlexN]

Originally Posted by peter_4059

I thought the MPCC was intended to correct coma in Newtonians rather than be used as a field flattener in a refractor?

"The only Newtonian Coma Corrector that does not change (increase) the focal length of the telescope in any way. f4 Newton optics will remain f/4!"

http://www.baader-planetarium.com/pdf/mpcc_e.pdf

I'm using a Baader MPCC to flatten the field of my TMB F/6 refractor. I looked at many other options (and spent quite a lot of money testing them...)

I finally decided I did not want any focal reduction (most flatteners are a 0.8x or 0.85x reducer as well) I was told by the previous owner of my refractor that an MPCC would flatten the field provided the distance from the chip to the MPCC was exactly the right distance.... I thought, it can't hurt to try it out... Gave it a go and have been using the MPCC since.. Perfectly flat field without any focal length reduction..