Astronomical values can vary
Distances, apparent sizes and observational circumstances change as objects move. Planetary reference values can also depend on the definition used, such as mean radius versus equatorial radius. Tools state the relevant convention where practical.
Models have limits
The Moon phase launch calculator uses a mean synodic cycle rather than a high-precision dynamical ephemeris. Telescope calculations describe optical relationships but cannot predict atmospheric seeing or the actual detail an observer will perceive.
Scientific work needs primary data
Researchers, observatories and anyone making precision measurements should use current primary datasets and specialist software appropriate to the task. Astronomy Times links to its major sources so visitors can verify the underlying references.