Astro Focus Filter for Stars & Planetary Photography

Method 1

1. Mount the Star Focus Filter onto your camera.
2. Turn on the live view mode, adjust the ISO to the biggest (ISO 1600 or above), and set the shutter speed to 10s or more.
3. Adjust the frame and make sure the bright star or light source is in the middle of the frame. It is recommended that you look for a bright star of magnitude 1 to focus on.
4. Magnify the frame and adjust the focusing rings at the same time until three fine spike lines show out in the frame.
5. Rotate the focusing ring to make the three spikes intersect at one point. This the when the precise focus is achieved.

Method 2

If you can't find a brighter star or the lens aperture is too small, you can take several testing pictures to get the focus.

1. Mount the Star Focus Filter onto your camera.
2. Adjust the focus rings to get an infinity focus
3. Set the high ISO and short exposure (several seconds), and take one testing shot
4. Check the three spike lines in the frame, if the central spike is closing to the left, screw the focus ring to the right. If the central spike is closing to the right, screw the focus ring to the left.
5. Take a second testing shot, and repeat step 4 until three spikes intersect at one point. Then a precise focus is achieved.

 Note: Hand holding the filter, then it can work with the lens without the adapter 

① Shoot — Frame the Right Star

Position a bright star (magnitude ~1 or brighter) in the center of your frame.
This helps the filter properly isolate and enhance the target star for the best optical effect.

② Set — Dial in Your Camera Settings

For optimal performance, always prioritize light intake:

• Use the widest aperture your lens allows
  
• For wide-angle lenses, shoot at maximum aperture
  
• Avoid stopping down unless needed for specific sharpness control
  

Recommended Aperture by Focal Length
10–11mm → F 1.2–2.5
12mm → F 1.2–2.8
14mm → F 1.2–3.5
16mm → F 1.2–4.0
18mm → F 1.2–4.5
20mm → F 1.2–5.0
24mm → F 1.2–5.6
28–600mm+ → F 1.2–5.6 or slower
💡 Note: These aperture recommendations are only for focusing with a Bahtinov diffraction pattern.

They are not your final shooting settings — remove the filter after focusing and shoot as normal.

③ Care — Protect Your Filter

To maintain long-term optical quality:

• Store in a protective filter case after use
• Keep away from high-temperature environments
• Clean gently if needed:
  Start with an air blower
  Use neutral lens cleaning solution for oil or residue
• Handle with care — the filter surface is not scratch-resistant