Editing Stellar parallax (section)

===Error===
Precise parallax measurements of distance have an associated error. This error in the measured parallax angle does not translate directly into an error for the distance, except for relatively small errors. The reason for this is that an error toward a smaller angle results in a greater error in distance than an error toward a larger angle.

However, an approximation of the distance error can be computed by
:<math>\delta d = \delta \left( {1 \over p} \right) =\left| {\partial \over \partial p} \left( {1 \over p} \right) \right| \delta p ={\delta p \over p^2}</math>
where ''d'' is the distance and ''p'' is the parallax. The approximation is far more accurate for parallax errors that are small relative to the parallax than for relatively large errors. For meaningful results in [[stellar astronomy]], Dutch astronomer Floor van Leeuwen recommends that the parallax error be no more than 10% of the total parallax when computing this error estimate.<ref name=van_leeuwen2007>{{cite book | first1=Floor | last1=van Leeuwen | title=Hipparcos, the new reduction of the raw data | volume=350 | series=Astrophysics and space science library | publisher=Springer | date=2007 | isbn=978-1-4020-6341-1 | page=86 | url=https://books.google.com/books?id=oU72XEf_5lEC&pg=PA86 | url-status=live | archive-url=https://web.archive.org/web/20150318002121/http://books.google.com/books?id=oU72XEf_5lEC&pg=PA86 | archive-date=2015-03-18 }}</ref>