Chromatic aberration in lens Is there a way to prevent chromatic aberration without using an achromatic lens in refracting telescopes or in any other instruments...?
It's probably impossible to prevent chromatic aberration, since there is no such thing as a perfectly achromatic lens. but you can certainly minimize it. 

As you have mentioned, for a given spectral range, the best way is to choose a lens that is said to be "achromatic" even though the correction is never perfect. 

But if you want to use a lens that is not achromatic, then you can try the following to reduce the chromatic aberration:


Use a lens that has a very long focal length, for more on that see How does making a refracting telescope very long reduce the chromatic aberration of an uncorrected lens? I figured out the answer there and will try to post an answer soon!
Minimize your spectral range with a filter, or at least cut out the short wavelengths (e.g. blue). The dispersion of glass is stronger at the shorter wavelengths.
If you are doing color astrophotography with a color sensor, then there may be a way to shoot the three color images separately, bringing each color into focus separately. One problem is that for color sensors used to reproduce human color perception, the red channel often has a blue bandpass to replicate the way color receptors in our eye work. See answers to Filter for RGB separation and its effect on the image and the image below. So if you are trying this, then it might be helpful to add a blue filter, at least to cut below say 425 nm.