The Focus tab provides a duplicate set of exposure controls, condensed into a compact format. While the Expose tab is used for taking images that will be saved, the Focus tab is primarily used for taking images for focusing and for centering objects in the field. The separate controls make it is easy to switch back and forth between two different exposure settings. The Focus tab can be used for the Main camera or the Guider, by clicking the appropriate radio button.
The Start Focus button starts an exposure or exposure sequence. When an exposure is in progress, the Start Focus button is disabled, and the Stop button is enabled.
The exposure duration is set using Seconds. The minimum exposure setting is 0.001 seconds. Note that some cameras cannot achieve this shutter speed and will use their lowest possible setting instead.
The Binning control allows you to combine multiple pixels together to produce “super-pixels” covering more area. The Delay(s) control specifies a delay time, in seconds, before each exposure is taken. For cameras that lock the computer during readout, it is a good idea to set the Delay to 1 to make sure there is enough time to stop a continuous exposure sequence. If Fast is checked, the camera plug-in is requested to favor speed of response over image quality. For DSLR cameras, turning on Fast Mode switches the image download from RAW format to JPEG format. If the camera plug-in in use does not provide a fast mode, this control is disabled.
The Subframe controls allow you to specify a limited area on the camera chip to be read out. This is useful for speeding up the readout when focusing. As with the Settings tab, you can drag the mouse on an image while holding the left button to draw the desired subframe area. This function is only available when the Focus tab is displayed. The Reset button restores the subframe settings to include the entire camera sensor. The Auto button locates the brightest pixel in the image and specifies a small subframe region around it.
The Dark check box enables automatic dark frame subtraction. A dark frame exposure will automatically be taken when required, and applied against all later images with the same settings. If the camera does not have a shutter, you will be prompted to cover and uncover the aperture as required.
The Continuous check box enables continuous imaging. When the Start Focus button is pressed, images will be acquired continuously until the Stop button is pressed.
A progress bar is included just below the Stop button. It illustrates graphically the progress of the exposure. Just below the progress bar is a status field which indicates the current camera activity.
The Focus tab is usually used in conjunction with the Inspect tab, which provides helpful information on the image focus. The Start Focus, Stop, and camera selection controls (i.e. Main/Guider radio buttons) are replicated on the Inspect tab.