expose

Command:	expose
Contexts:	Network socket, serial console, stage2 only
Function:	Take an exposure (integration)
Required Parameters:	None.
Optional Parameters:
nowait	Starts a non-blocking exposure. If specified, expose command exits before exposure is complete. Remaining exposure is handled in the background allowing the controller to process other commands during exposure. (>= r5641 stage2 ONLY)
abort	Aborts any non-blocking exposure currently in progress and closes the shutter. (>= r5641 stage2 ONLY)

Usage

This command is used after setting up parameters for an exposure. The last etype and etime commands used since the controller booted will apply. For example, a 45 second DARK exposure (no shutter activation) is performed as follows:

etype dark
etime 45000
expose

This command is typically preceded by clean and followed by readout.

By default, the expose command does not exit until the exposure is complete. This blocks the controller from handling any other commands for the duration of the exposure.

As of stage 2 r5641, an optional nowait parameter is available to allow the exposure to be handled in the background without blocking command handling during the exposure. For example, a 30 second OBJECT exposure run in the background would be performed as follows:

etype object
etime 30000
expose nowait

The status of the exposure can then be polled with the exposing command.

If an exposure launched in the background needs to be stopped prematurely before the entire etime has elapsed, the abort option can be specified to cut the exposure short and close the shutter:

expose abort

Aborting the exposure will result in an unpredictable exposure time. The actual shutter close time (and thus exposure duration) can be determined with the exposing command.