Everything we know about getting stars sharp, written down so you don't have to learn it the hard way. Start with whichever question is keeping you up at night (besides the stars).
Choosing your gear
Bahtinov Mask vs. Tri-Bahtinov vs. Kase Filter: Which Do You Need?
A side-by-side comparison of clip-on masks, the Tri-Bahtinov collimation mask, and the Kase magnetic filter, with a quick answer for every setup.
How to Choose the Right Bahtinov Mask Size
How to measure your lens or telescope in thirty seconds, plus a size chart for every mask and filter we sell.
Getting started
How to Use a Bahtinov Mask
The basics, step by step: attach the mask, read the diffraction spikes, and lock in perfect focus.
How to Focus on the Stars at Night for Astrophotography
Getting a camera to focus on a pinpoint of light in the dark, from first setup to final shot.
Why Your Lens's Infinity Mark Isn't Really Infinity
Why turning your lens to the ∞ symbol gives blurry stars, and how to find true infinity in under a minute.
Sharper results
How Often Should You Refocus During an Imaging Session?
Temperature drops, filter changes, meridian flips, and the other reasons focus drifts over a night, plus a one-minute fix.
How to Focus for Star Trail Photography
Sharp, thin trails or soft, bold ones: where to focus, and how to hold it steady for hours.
Troubleshooting: My Bahtinov Pattern Looks Wrong
Missing spikes, faint patterns, extra spikes, and a center spike that refuses to center, solved.
Telescopes
How to Collimate a Telescope with a Tri-Bahtinov Mask
Check focus and mirror alignment on a single star. For SCTs, Newtonians, and Ritchey-Chrétiens.
Safety
Solar Safety: How to Observe and Photograph the Sun Safely
The rules for solar filters, eclipse glasses, and finder scopes. Read this before pointing anything at the Sun.
Want more?
Our blog, The Johannes Space Guide, covers astrophotography beyond focusing: the Milky Way, planets, deep-sky objects, the Moon, meteor showers, and more.
Have a question we haven't answered? Email us at Support@bahtinovmask.com. If enough people ask, it becomes the next guide.