Exposure time¶

exptime [ <time> [ s | ms ] ]

Sets the exposure time, or reports it when given no argument.

A bare argument is interpreted in whatever unit LONGEXPOSURE selects, and the reported value uses that same unit. An explicit s or ms suffix overrides it for that one command, so exptime 500 ms means the same thing whichever way the instrument is configured.

Key	Default	Meaning
`LONGEXPOSURE`	`true`	`true`: bare `exptime` arguments are seconds. `false`: milliseconds.
`EXPTIME_MSEC_PARAM`	none	Archon parameter holding the milliseconds part. Required.
`EXPTIME_SEC_PARAM`	none	Archon parameter holding the whole-seconds part. Optional.

Internally the exposure time is always held in seconds, which is also the unit of the EXPTIME FITS keyword, so the configured unit never changes what ends up archived.

Warning

Archon parameters are 20 bits. Without EXPTIME_SEC_PARAM the whole exposure time has to fit in the milliseconds parameter, capping it at 2^20 msec, about 1048 seconds. Beyond that exptime returns an error rather than silently leaving the controller and the FITS header disagreeing.