3D print of a Bahtinov filter

Optical focus

When you take photos, you need to focus. So when I go out at night to do astrophotography, I also need to focus.

No need to say, my collected data is shit when I don’t do it properly. Shooting stars do not give room for mistakes, even tiny ones.

And I struggle so hard to focus with manual lenses for astro (the autofocus does not work in such dark situations! Thus, I shoot with 1960s-1990s lenses from the USSR with a 2015 camera; So no autofocus anyway).

One would say

“Leave the old stuff, buy a real tube, equatorial mount & motorized focuser stuff”. — Michmich

Yet, I’m not considering switching my 5kg backpack for a 25kg rolling case.

And this night, I discovered the Bahtinov mask!

Bahtinov

The Bahtinov mask creates a diffraction pattern when put in front of a lens.

Source: Wikipedia

The super awesome thing about it is that the visual artifact tells you which direction you need to roll the focus ring to sharpen the picture.

I want one.

Making one

Pain in the ass; The filter is tricky. It mainly depends on the camera focal length. And it would be cool to have the correct diameter for lenses.

Won’t buy one, time to 3D print mine!

I love the open-source world. My 3D printer is fully open source. The Bahtinov might be. My first exploration led me straight to the marvelous Thingiverse. And especially here: Bahtinov Mask For Samyang 135mm Lens.

And just like that, I downloaded OpenSCAD, forked the project & tweaked it.

3D printing

Like always, I struggle so hard to scale my prints when size matters (what are you thinking?). So I first print the object upside down to print the ring first, kill the print, check the diameter with my lens & adjust.

Took me six shots to get the expected inner diameter. Does my printer suck?

Closing

I made my DIY Bahtinov mask in 4 hours, almost including this blog writing (nope at all). OpenSCAD kinda blew my mind: code, variable, versioning; that’s promising! Blender will stick to arts.

I owe a coffee to dakloifarwa for the OpenSCAD source code!

You are still here? Bonus!

Let’s code my first real OpenSCAD code — I need a lens cap!

I printed it with wood, so fancy. Find this print on Thingiverse.