Why are my astrophotos blurry or trailed?
Tracking and Rotation
The Earth rotates, so stars appear to move across the sky. Without tracking, long exposures cause star trails. Even with tracking, misalignment or periodic error can cause trailing. For deep-sky objects, you need a motorized equatorial mount that rotates at the same rate as Earth. Alt-azimuth mounts can also track but may cause field rotation over time.
- Polar align your equatorial mount for accurate tracking.
- Use a guidescope and autoguider for longer exposures.
- Keep exposures short if your mount is not accurate.
Focus and Stability
Poor focus makes everything soft. Use a Bahtinov mask or live view to focus precisely. A shaky tripod or wind can also blur images. Make sure your mount is stable and on solid ground. Avoid touching the telescope during exposure. Use a remote shutter or delay.
- Focus on a bright star before shooting your target.
- Lock mirror up if using a DSLR to reduce vibration.
- Shield your scope from wind if possible.
Atmospheric and Optical Issues
Atmospheric turbulence (seeing) can blur fine details, especially for planets. Let your telescope cool to ambient temperature to avoid tube currents. Dew on the lens can also cause blur; use a dew heater or shield. Ensure your optics are clean and collimated.
- Check the seeing forecast; good nights are rare.
- Allow 30 minutes for a reflector to cool down.
- Collimate your telescope regularly for sharp images.
Common mistakes
- Assuming all blur is from tracking; focus and stability are equally important.
- Using a flimsy tripod meant for terrestrial photography.
- Ignoring atmospheric conditions; even perfect gear can't overcome bad seeing.
