In response to the above question, Aki writes: I recommend as an easy default option real nu; nu ~ gamma(2,0.1); This was proposed and anlysed by Juárez and Steel (2010) (Model-based clustering of non-Gaussian panel data based on skew-t distributions. Journal of Business & Economic Statistics 28, 52–66.). Juárez and Steel compere this to Jeffreys […] The post “Do we have any recommendations for priors for student_t’s degrees of freedom…