====== Preview Tool ======

{{:en:documentation:tool_preview.png}}

This tool is to take a preview exposure for focusing or centering purpose.

Set the **Exposure time** and the **Binning** to use for the preview. \\
You can also change the **Gain** and **Offset** or the "ISO" if supported and activated in the [[preferences#camera|options]]\\
The camera lens **F-Stop** when using a supported INDI DSLR.

This setting is totally independent of the [[Capture]] setting.

Click **Preview** for a single exposure or **Loop** to take exposure continuously until you stop it with the same button. The light change to green when the loop is active.


The Option on top let you select an action to do on every preview image.

  ***Astrometry** , every preview image is solved and the current center coordinates are shown at the bottom of the preview tool:\\ {{:en:documentation:tool_preview2.png}}

  ***Image inspection** , show the [[collimation#image_inspection|image inspection]] overlay.

  ***Stack** , visible only if you activate the "stacking option" in the [[preferences#camera|preferences]] \\ When it is checked, every preview loop frame is added to the previous ones. If available the images are processed with [[dark_frame|Dark]] and [[bad_pixel_map|BPM]]. If the option is activated the frames can be aligned. \\ \\ After you start the Loop, you see the object image to appear progressively in the screen as the number of frame increase. This function is often use in public demonstration.\\ \\ You can use the menu [[save_fits_file|File/ Save FITS file...]] to record the stacked image after you stop the Loop. \\ A new stack is started when you restart the Loop.

  ***Preprocessing** , preprocess every image with the loaded [[dark_frame|dark]] and [[flat_frame|flat]] frames.

When the FITS file contain multiple image extension it is possible to navigate from one image to the other using the arrow at the bottom.