Star Focus Assistant
Star Focus Assistant is compatible with Lion, Mountain Lion (10.7) and higher.

Star Focus Assistant is compatible with Win 7 and higher.

If application does not respond to key strokes, you need to reboot Mac.

Brief Description:
"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. "Star Focus Assistant" does this by tracking a slowly moving bright spot (your focus star) and magnifying dynamically a portion of your display. "Star Focus Assistant" uses pixel information from this "Live View" image. Star Focus Assistant is $20 shareware. Users can try Star Focus Assistant in Demo Mode for up to ten launches before registration is required.

Mac Version 2.3.0 is compatible with Normal and Retina Displays. Windows Version 1.0.1 is a bug fix.


When you launch "Star Focus Assistant" you see a small "Control Panel" and a larger "Display Window".

"Star Focus Assistant" operates in two modes: "Normal" and "Auto Track".

In "Normal" mode, the "Display Window" background displays a magnified view of the desktop area around your cursor. As your cursor moves around the screen, you see the image inside the "Display Window" change as well. Located in the middle of the "Display Window" is a "Red Box" that surrounds the nine cells around your cursor. This "Red Box" identifies the cells used by the tracking algorithm.

In "Auto Track" mode, you identify a bright spot you want to track across the display, move the cursor over this spot and then press the "Command-Option" keys (for Mac; Alt-Right Cursor for Windows) to activate the automatic tracking function. You will see "AT Mode" displayed in red font above the "Magnification" up/down selector in the "Control Panel". A specially developed algorithm will keep your cursor close to the bright spot as it moves. To leave the "Auto Track" mode so that you can use your mouse and cursor for other computer operations, press the "Command-Control" keys (for Mac; Alt-Left Cursor for Windows) to revert to the "Normal" mode.

The "Control Panel":
There is a button (Mac version only) to "Show" or "Hide" the "Display Window".

There is an up/down selector to increase or decrease the "Magnification" level (10x to 30x) of the computer display area inside the "Display Window".

Using "Star Focus Assistant" In The Field: (Note: The instructions listed below use Canon's EOS Utility program and its "Live View" viewing capability to illustrate how to use "Star Focus Assistant" in the field. Other camera manufacturers may have similar utility programs for their cameras equipped with the "Live View" feature.)

Setup your camera and computer just as you would for any typical imaging session.

Select a bright star to use for your focus routine.

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.

With your focus star centered, click on the 10x magnification button in the lower right corner of the screen (Canon EOS Utility).

Launch "Star Focus Assistant" and position the "Control Panel" and "Display Window" off to the side.

Place your cursor near your target star. You will see the area around your cursor appear inside the "Display Window". Place your cursor inside the star's bright center and press the "Command-Option" keys (for Mac; Alt-Cursor Right for Windows) to activate the "Auto Track" feature. "Auto Track" will now keep the star's image inside the "Display Window" so that you can concentrate on focusing your camera lens.

As you rotate your camera lens's focus ring, notice that the image in the "Display Window" is surrounded by red or blue pixels. This indicates that the image is out of focus. When the image is as white and free from colored pixels around its periphery as possible, your image should be in focus. From this point forward, don't touch the focus ring on your lens.
Quit "Star Focus Assistant". Take some great pictures!


Above you see "Star Focus Assistant" keeping Sirius in the "Display Window". The Magnification setting is 15x. Starry Sky Enthusiast was used for this screenshot. The Starry Sky Enthusiast Zoom was zoomed to setting 5 degrees x 3 degrees. Grab was used to take the screenshot with its Preferences set to show the mouse.

Operational Notes:
Set the "Control Panel" controls to your preferred settings before you begin your night's imaging activities (previous settings are retained).

Drag the "Control Panel" and "Display Window" out of the way. You can resize the "Display Window" by dragging its bottom right corner.

As long as "Star Focus Assistant" is running and you can see the "Control Panel" window (not minimized), you can "Hide/Show" the "Display Window" by clicking the "Control Panel" button (Mac version only) or pressing the "Option-Shift" (for Mac) (to Hide) or the "Control-Shift" keys (for Mac) (to Show).

Quit "Star Focus Assistant" by closing the "Control Panel" window. "Control Panel" "Magnification" setting and locations of the "Control Panel" and "Display Window" are saved automatically between sessions.

A special thanks to Darryl Hedges who suggested this interesting and challenging application, provided the technical information, and served as Beta Tester.

Click here to download Version 2.3.0 (3.1 MB) for Macintosh, OS 10.7 or later (zip).

here to download Version 1.0.1 (1.3 MB) for Win 7, Win 8, and Win 10.