EPOCH query parameter

[molinaro-m]

As expressed in this DAL (quite old) mail thread to query the sky at a given epoch.
(connected also to solar system use cases)

[mbtaylor]

This looks complicated to me. Only a minority of services will be able to do anything with an EPOCH parameter, namely, those with proper motion information. So a client submitting an EPOCH parameter to the query will in general not know whether the service has honoured it or ignored it. The use case mentioned in the quoted email of locating objects corresponding to 100-year-old positions is a fairly specialist one, and could be addressed by widening the cone to accomodate even fast moving objects over the relevant interval, and then performing corrections on the client side.

For a "simple" protocol like SCS my inclination would be to avoid this level of complexity.

[Bonnarel]

as in input PARAMETER it looks complicated as Mark states. (except maybe if this work as a selection of epochs available in the service without any recomputation)
For the response however the epoch of coordinates should be given in appropriate attribute of the COOSYS element

[msdemlei]

On Wed, Sep 02, 2020 at 02:07:41PM +0000, Mark Taylor wrote: For a "simple" protocol like SCS my inclination would be to avoid this level of complexity.

+1 (and: ADQL UDFs may help, too, if widening the cone doesn't cut it).