The phrase "ascertain how far" is correct and usable in written English.
You can use it when you want to determine the extent or distance of something, whether literal or figurative.
Example: "We need to ascertain how far the project has progressed before making any decisions."
Alternatives: "determine the extent" or "find out the distance".
Experts are trying to ascertain how far the underground cavity reaches and whether more homes are at risk.
The aim of this study was to ascertain how far the production-induced reduction of the encapsulation rate relates to the size of inner water droplets and to evaluate the relevance of multiple emulsions as drug carrier for diclofenac sodium.
Although the scientific method will eventually converge to something as a limit, nevertheless at any temporal point in the process of scientific inquiry we are only at a provisional stage of it and cannot ascertain how far off we may be from the limit to which we are somehow converging.
(10) Further sediment studies are necessary, similar to those carried out in the open Baltic Sea, 10) to ascertain how far back in time hypoxia was observed in the coastal zone.
Examine your city's building code to ascertain how far away from your home you must place your hot tub.
First he ascertains how far off the compass is; next he tracks down sources of distortion, most of which can be taken care of by a built-in compensator.
However, one can ascertain how close or far a neuron sits from its tipping point based on whether controlled manipulations succeed in forcing the neuron across that point.
See how far we have come?
It will be interesting to ascertain how these effects are compounded in aneuploid cancer cells that frequently contain far more than just the one numerical aberration as in our model system.
How might I be perceived?" And use supervision to ascertain how others perceive you.
