refractors have a problem because they lens splits up the different wavelengths of light so that they do not focus at the same point.
To correct this telescope designers use glass called ED glass which is also used in the best quality camera lenses.
Even better is a mineral flourite, the material is made in a lab and is very expensive.

You might want to also consider Maksutov designs which are reasonably priced. They have long focal lengths and good for observing planets and double stars.
Meade has a Schmidt Newtonian design which is a reflector with a corrector plate. It is a short focal length and would be good for observing galaxies, nebulae and clusters.