Mastering Afocal Astrophotography with Your Phone

Afocal astrophotography, the technique of holding your phone camera up to a telescope eyepiece, is an accessible way to capture celestial wonders. However, many newcomers face common hurdles like vignetting (the black circle), image shake, and getting the right camera settings for planets. If you've been encountering these issues, you're not alone!

Tackling the Black Circle (Vignetting)

The circular field of view with a black border is a common sight when starting out. This often happens because the exit pupil of your eyepiece is larger than your phone's camera lens. Here are some solutions:

• Experiment with Eyepieces: Try using eyepieces with a smaller focal length (like your 9mm) as they might produce a smaller exit pupil that better matches your phone lens.
• Wide-Field Eyepieces: For a truly immersive image without the black border, an eyepiece with a very wide field of view is ideal. While these can be expensive, they offer a significant improvement.
• Phone Zoom: Some users find that utilizing their phone's built-in optical or even digital zoom can help fill the frame and reduce the black border. Be mindful that digital zoom can degrade image quality.

Achieving Sharper, Less Shaky Images

Stability is key to sharp astrophotography. Here's how to minimize blur:

• Remote Shutter/Delay: To avoid vibrations from pressing the shutter button, use a timer delay on your phone or a remote shutter (some smartwatches offer this functionality).
• DIY Phone Mounts: While dedicated adapters like the Tridaptor are recommended for stability, you can experiment with DIY solutions. Think about sturdy clamps or makeshift supports that firmly hold your phone in place against the eyepiece.
• Bahtinov Mask: For razor-sharp focus, especially on bright stars, a Bahtinov mask is invaluable. This tool helps you precisely determine when your image is perfectly focused.

Optimizing Phone Settings for Planets

Capturing planets like Jupiter and Saturn requires a different approach due to their brightness:

• Manual Control is Essential: You'll need a camera app that allows full manual control over exposure, ISO, and focus. Apps like NightCap (for iPhone) or similar manual camera apps on Android are crucial.
• Reduce Exposure: Planets are bright! You'll need to drastically reduce your exposure time, often to fractions of a second (e.g., 1/50s) and keep your ISO low. Experimentation is key to finding the sweet spot.
• Video is Your Friend (Lucky Imaging): Instead of single photos, record short videos. This technique, known as lucky imaging, captures many frames. Later, you can use specialized software to stack the best frames, effectively averaging out atmospheric turbulence and noise to reveal finer details.
• Raw Capture: If your phone supports it, shoot in RAW format. This provides more flexibility during post-processing.
• Motion Detection Apps: For capturing raw video data, apps like Motioncam can be useful, allowing you to extract individual frames for stacking.

Software Workflow for Planetary Imaging

Once you have your video footage, a typical workflow involves:

1. Video Capture: Use a manual app or specialized video app (like Motioncam for raw footage if supported).
2. Frame Extraction: Extract individual frames from your video.
3. Stacking: Use software like PIPP (Planetary Imaging Pre-processing) to align and stack the best frames.
4. Processing: Further refine the stacked image with software like AutoStakkert! or RawTherapee to enhance details.

Afocal astrophotography with a phone is a journey of experimentation. By understanding these principles and applying the tips above, you'll be well on your way to capturing stunning images of the night sky!