I am trying to build a lens... a simple lens... i would like to have a 750 to 1000mm i would prefer to have a simple construction, but a positive meniscus have a lot of difusion... would a steinhel periskop be any better? built out of 2 positive meniscus around a diafragm? or an achromat doublet? or an achromat doublet on either side of a diafragm...
also where can i buy lenses to make a photo lens of this type (cheap)