Star Focus Assistant is a utility developed to help astrophotographers using a DSLR camera focus their camera while viewing an object in real time. This requires that your camera have the ability to send a real time or "Live View" image to your computer so that you can see your "target" image change focus as you turn the focus ring on your camera lens.This program does this by tracking a slowly moving bright spot (your focus star) and magnifying dynamically a portion of your display. It uses pixel information from this "Live View" image.

Use whatever program works for you (e.g., Canon EOS Utility, Nikon Camera Control Pro, etc.) to set your camera to BULB, the lowest F-stop for your lens, and an ISO of 1600 or so.

Activate the "Live View" feature on your camera. In the EOS Utility program, select "Camera settings / Remote shooting", then the "Tool" menu selection at the top of the screen, then the "Remote Live View shooting" option from the drop-down menu and center your focus star in the display.

Limitations:
* 10 runs trial

The license of this software is Free Trial Software, the price is $20.00, you can free download and get a free trial.