don't care about the shape of input object
actually for speed, try more typical case first
added to_units method and test
uhm?
remove old observe test
added a test to see that frame conversion working
added gaia spitzer errors function to observation
remove placeholder observe function
reworked up to observing particles
added new method for observing particles
no need for error model
remove error model import
forgot key to dict
adding test to plot observing
fix test input
add one other check to observe test
observe particles and satellite
change micro to milli
added repr to particle
fix nparticles for one particle