Kevin_A those cheap 3D printed and standard masks are totally useless!
Is this your 135mm Rokinon or some shorter focal length one?
I have some half dozen of the etched 82mm and 100mm x 100mm Bahtinov masks, and found all of them to be much better than the free junk plexiglass on the WO tube caps, and the Astrodymium 3D printed ones.
All of them show good central star to different degrees. The 3D printed stuff are too rough to produce a small, clean central star that you can actually use to judge if the central spike of the Bahtinov diffraction pattern actually passes through it. The stuff that comes in the WO caps are completely hopeless, and comes with chromatic artifacts to boot (what do you expect from the dispersion of plexiglass?!).
If you have a lens that is shorter than perhaps 85mm, then nothing but the wide-angled one from Hungary works across the entire wide FOV.
With a standard single-pattern mask (whether glass, plastic or metal), stars near the corners will show fewer than the 6 symmetrical spikes. The Hungarian ones, both wide and tele versions, are patterns on a photographic negative (he probably used 4x5 negatives) that is sandwiched between plexiglass. The wide-angled one is made up of a mosaic of smaller Bahtinov masks, so that even skewed rays from corner stars of a wide angle lens will see all three patterns of a Bahtinov mask. The wide-angled one does not work with longer lenses, by the way.
So far, I have found both the Hungarian ones (since it is really precise, fine high resolution photographic negatives that produces very bright and humongus sized spikes) to be palpably superior to the others. Only disadvantage is the format (100x100mm) and paying for DHL shipping across the pond.
But, if you have your backfocus already adjusted so all stars achieve focus at the same place of the drawtube, all you need is to focus a star near the optical axis, in which case, all the 82mm round glass filters will work fine.
The 100mm x 100mm ones all really have only 77mm to 82mm worth of Bahtinov patterns.
If you have a really large lens filter thread, I have only found ones from Maven. But they also produce all 6 spikes only in the center of the field for a wide-angle lens. I have adapted their 95mm one for my Baby-Q, using a Thousand Oaks solar filter that sacrificed itself to have some step-up and step down rings glued to it to take the 95mm thread.
https://mavenfilters.com/product/starry-focus-filter/
Maven takes forever to ship, though.
Chen
