Skywatcher Mak 127 solar filter — magnetic quick release (Baader AstroSolar)

A 3D-printable solar filter for the Skywatcher Mak 127, built around Baader AstroSolar Safety Film OD 5.0, with a magnetic quick release so it can be pulled off and put back without touching the telescope.

It was designed for the total solar eclipse of 12 August 2026: totality lasts around ninety seconds, and the filter has to come off the moment it starts and go back on before the first sliver of photosphere returns. Unscrewing something is not an option, and any force on the tube shifts the framing.

Full build write-up, with the mistakes included: https://www.elcacharrista.com/en/articles/solar-filter-for-mak127/

⚠ READ THIS BEFORE PRINTING

Looking at the Sun through an unfiltered or badly filtered telescope causes permanent blindness, and it does not hurt while it happens. This is a printed holder, not a certified filter — the safety comes entirely from the film you put in it and from how carefully you check it.

• Use only genuine solar film rated OD 5.0 / ND 5 (Baader AstroSolar Safety Film or equivalent). Never welding glass of the wrong grade, exposed negatives, smoked glass, sunglasses or CD/DVDs.

• Never use a screw-in "solar filter" that goes on the eyepiece. The filter always goes at the front, covering the full aperture.

• Inspect the film against a bright lamp before every single session. Any pinhole, scratch or tear means it goes in the bin. Not "it's just a small one".

• Cover or remove the finder scope. It is an unfiltered telescope of its own and it will burn whatever is behind it.

• This is a magnetic quick release — it is designed to come off. Check the hold with your own magnets and your own printed tolerances before pointing at the Sun, and never leave the telescope unattended, especially around children or animals.

• Print it in PETG or better. PLA softens in the sun.

You are responsible for verifying your own build. If you are not sure, buy a commercial filter — they are not expensive.

Parts

You will also need

• Baader AstroSolar Safety Film OD 5.0 — an A4 sheet is enough for several filters

• Neodymium magnets, 6 mm diameter × 4 mm tall — [QTY]

• M3 screws and heat-set inserts — [QTY]

• Self-adhesive foam pad / weather stripping, for the friction fit

• Cyanoacrylate (superglue)

• A standard 6 mm office hole punch

• A permanent marker

Print settings

PETG, 0.2 mm layer height, 0.4 mm nozzle. No supports on any part.

Everything fits a 180 × 180 bed (Prusa Mini), but two parts need help:

• filter_base — rotate 45° on the bed. With the tab it is ~195 mm across and will not fit straight. It also needs a print pause to drop the magnets into their pockets. Glue each magnet with superglue before resuming: some of them will otherwise jump up and stick to the nozzle mid-print. Ask me how I know.

• filter_cell_front — print it flipped, Sun-facing side down, so the film recess opens upward and only the small screw countersinks have to bridge.

• dust_cap — also rotated 45°. Its magnets are glued in after printing, not buried, so the pull stays strong across the extra gap.

• tube_plug — brim flat on the bed, stem upward.

Assembly

1. Set the heat-set inserts into the rear cell half with a soldering iron.

2. Stick the foam pad inside the base ring and test the fit on the tube before anything else.

3. Print the template, trace the outline onto the film with a permanent marker, cut it out and punch the holes with the 6 mm punch.

4. Sandwich the film between the two cell halves and close them with the M3 screws. The screws pass through the punched holes and locate the film.

Do not tension the film. It should sit loose, wrinkles and all. The film expands and contracts with temperature, and Baader's own instructions call for it to be mounted free from strain — wrinkles do not degrade the image, tension does.

The whole thing is parametric OpenSCAD, so the diameter can be adapted to other tubes. Ask if you want a size that is not here.