Dumb question- Chromatic abberation correction.

Using a refractor with a doublet objective...is there any color correcting lenses that can be added BETWEEN the EP and the objective to bring the red or blue into actual alignment, or would better align those colors?.

'can't afford a 6" triplet...or ANY triplet for that matter.

As the Royal "Simba" would say....what is swallowed going in must come out.

I'm assuming you're talking about a standard crown/flint achromat? if so and it's the proper scope, then a chromacor would do fine. There are other types of doublets that will show no false color over the visual range (My AP Star 130 ED is an example--in the visual light range of the human eye, it's perfect. In the UV and IR areas, it ain't so hot, but those I always filter out during imaging sessions anyway. The third lens would bring those outer ranges to focus better. Takahashi FS series scopes for example are doublets, only made from fluorite and ED glass. even with a triplet apo, you will still experience some focus shift due to atmospheric refraction; I always refocus my individual colors when rgb imaging. Refocusing on a simple achromatic design will not help, as the blue and extreme red will never quite focus correctly.