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Description
Planetary Nebula distance scales often suffer for model dependent solutions. Model independent trigonometric parallaxes have been rare. Space based trigonometric parallaxes are now available for a larger sample using the second data release of Gaia. We aim to derive a high quality approach for selection criteria of trigonometric parallaxes for planetary nebulae and discuss possible caveats and restrictions in the use of this data release. A few hundred sources from previous distance scale surveys were manually cross identified with data from the second Gaia data release (DR2) as coordinate based matching does not work reliable. The data are compared with the results of previous distance scales and to the results of a recent similar study, which was using the first data release Gaia DR1. While the few available previous ground based and HST trigonometric parallaxes match perfectly to the new data sets, older statistical distance scales, reaching larger distances, do show small systematic differences. Restricting to those central stars, were photometric colors of Gaia show a negligible contamination by the surrounding nebula, the difference is negligible for radio flux based statistical distances, while those derived from H-alpha surface brightness still show minor differences. The DR2 study significantly improves the previous recalibration of the statistical distance scales using DR1/TGAS.
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