Astro Focus Guide
Base Settings for Focus Setup
ISO: 3200–6400
Aperture: Wide open (f/2.8 or wider)
Shutter: 5–10 sec (for preview only)
Focus Mode: Manual (MF)
Stabilization: OFF (lens & body)
Display Brightness: Low (preserves night vision)
Manual Focus Workflow
Point at the brightest star or planet (or distant light on horizon).
Enable Live View — switch to full manual exposure for brightness.
Zoom in digitally (10x) on the target light source.
Turn focus ring slowly until the star becomes smallest and sharpest.
NOTE: Look for minimum star size, not brightness.
Take a test shot (5–10s). Zoom to 100% and inspect star shape.
Fine-tune focus with small adjustments & repeat test shot if needed.
Pro Tips & Tools
Use Focus Peaking? Only works after you’re close. Don’t rely solely.
External Monitor: Great for better resolution and visibility.
Star Too Dim? Try:
Brighter planet (e.g., Jupiter, Venus, Sirius)
Distant lit structure or mountain ridge silhouette
Verify Focus Is Perfect
Zoom to 100%: Star should be round, not soft or bloated
Check corners: Fast lenses show coma—still aim for sharp center
Compare test shots: Slight defocus looks almost right—check closely
Lock It In
Switch to MF mode if using AF lens
Use gaffer tape on the focus ring (weather-safe)
Disable lens communication (if it resets focus)
Avoid touching the lens/camera after focusing
Pitfalls to Avoid
Infinity mark is unreliable — never trust it
Cold temps shift focus — recheck after cooling
Camera shake during focus — use sturdy tripod & delay timer
Forget to lock focus — accidental bumps can ruin shots
Field Checklist
Run through before each series:
◻️ Bright star/target located
◻️ Live View on + 10x zoom
◻️ Focus ring set to smallest star point
◻️ Test shot at 100% zoom reviewed
◻️ Corners checked for coma/star shape
◻️ Focus locked/taped
◻️ MF mode confirmed
◻️ Lens comm. disabled (if needed)
One perfect focus = hours of clean stars.
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