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Camera & Lens

Sample Frame @ Bortle 8.5

M45 (Pleiades), invisible to the naked eye from a Bortle 8.5 sky in Chennai, India. The camera captures it clearly in a single short exposure. Naked-eye limiting magnitude here is around 2.3 mag; the camera reaches about 6.3 mag. Four magnitudes of improvement means roughly 40× more stars in the frame, plenty for a reliable plate-solve.

Sample Frame

  • Bortle 8.5 city sky (Chennai, India), under a hazy light-pollution dome.
  • Naked-eye visual limiting magnitude here: around 2.3 mag.
  • Sensor + F2.4 lens captures stars down to about 6.3 mag in this sky, with good plate-solve confidence.
  • More than 40 stars detected per frame, well above the threshold for a reliable solve.
  • Rule of thumb: each magnitude of fainter detection adds roughly 2.5× more stars in the frame, so 4 magnitudes ≈ 40× more visible stars.

Quick Specs

QUICK SPECS

Camera:       OV9281, 1MP mono, USB UVC
Lens:         M12, 25mm, F/2.4
FOV:          8.86° × 4.98°
Pixel scale:  24.9″/px
Plate-solve mag (Bortle 8.5):  ~6.3
Cost:         $41 USD (camera + lens)

Supported Hardware

Currently support is provided only for this specific combination of camera and lens:

These are reference suppliers. The OV9281 module itself is widely sold by Arducam, Innomaker, AliExpress and others, and any M12 25mm F/2.4 lens with the correct mount works. If a link above goes dead, search the sensor name (OV9281) and lens specs and pick any reputable seller — the parts themselves are commodity.

Why This Camera and Lens

  • Off the shelf, affordable, and widely available
  • For use in urban light polluted skies:
    • Mono sensor provides substantially better sensitivity and contrast for star detection compared to a color sensor
    • F2.4 aperture provides good light gathering power required to detect faint stars in light polluted urban skies
    • 25mm focal length in combination with the OV9281's 1/4" sensor size provides a ~8° field of view which is a good balance between having enough stars for reliable plate-solving and speed of solving
    • In my Bortle 8 city sky with a visual limiting magnitude of around 2.5, this camera/lens combo can reliably detect and plate-solve on stars down to about magnitude 6.5
  • Standard USB (UVC) interface allows for cross-platform compatibility without needing custom drivers
  • Calculated image scale and field of view (Astrometry results):
    • Size: 8.86° x 4.98°
    • Radius: 5.081°
    • Pixel scale: 24.9 arcsec/pixel

Currently only this specific camera and lens combination is supported. Support for additional cameras and lenses may be added in the future based on demand and usability. I decided to keep it this way for now to ensure a consistent and reliable user experience. Also this combination is very affordable and widely available, so it should be accessible for most users.

Adding Support for More Cameras

  • Adding the camera's VID/PID to the camera server's supported device list and implementing any necessary quirks for frame capture (if required)
  • Generating the tetra3 star database for the new camera/lens's field of view and plate scale.