• Long-Exposure Deep-Sky Imaging
  • Planning the Imaging Session
  • Equipment Setup
  • Camera Settings
  • Polar Alignment
  • Focusing
  • Target Acquisition and Framing
  • Guiding vs Tracking
  • Image and Support Frames
  • ISO and Exposure
  • Data Acquisition
  • File Formats, Downloading and Archiving
  • Cheat Sheet

• Filtered Shots

• High-Resolution Planetary Imaging

For exposures of about 1 to 5 minutes and at focal lengths of 100mm and longer, an equatorial mount and more accurate polar alignment is required.

At these long exposures and longer focal lengths, it may also be necessary to guide the imaging scope on a star during the exposure. A high-power cross-hair eyepiece is used to keep the star exactly centered, or an auto-guider is used to do this automatically with a computer.

Guiding requires either a separate guidescope or an off-axis guider which uses a small mirror in the light path just before the camera to pick off some of the light that includes a star so the scope can be guided through the same optical system that is doing the imaging.

The Learning Curve

• Learn how to correctly focus your camera at prime focus of your scope.

• Start taking astrophotos at the prime focus of your scope and manually guide them with a piggy-back refractor guidescope on top of your main imaging scope.

• Master prime focus and manual guiding techniques.

• Get an autoguider or webcam and learn how to autoguide.

• Master the technique of prime-focus deep-sky astrophotography with an auto-guider.

• Relax and enjoy the beauty of the night sky while the auto-guider does all the work.

• Learn how to digitally process your astrophotos.

• Enjoy the satisfaction of your accomplishments and share the beauty of the universe with others.

Once you have mastered the intricacies of polar aligning, critical focusing, and tracking and guiding at long focal lengths, you will be able to vastly improve your images by shooting longer exposures, and more of them, to gather more photons to increase the signal-to-noise ratio in the final image. This will allow imaging of much fainter objects.