What's Changed
* Fixed a bug where obs coordinates were being interpreted as being on cell centers instead of cell vertices. by byrdie in https://github.com/sun-data/interface-region-imaging-spectrograph/pull/19
* Added `iris.sg.SpectrographObservation.timedelta` field which stores the exposure time for each frame of the observation. by byrdie in https://github.com/sun-data/interface-region-imaging-spectrograph/pull/20
* Added `iris.sg.SpectrographObservation.radiance` property which converts from DN to radiometric units. by byrdie in https://github.com/sun-data/interface-region-imaging-spectrograph/pull/21
* Bump `named-arrays` to version 0.16.0 by byrdie in https://github.com/sun-data/interface-region-imaging-spectrograph/pull/22
**Full Changelog**: https://github.com/sun-data/interface-region-imaging-spectrograph/compare/v0.4.0...v0.5.0