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

File

What it is

mak127_solar_filter_base.stl

The ring that stays on the telescope. Friction fit, holds the magnets

mak127_solar_filter_cell_rear.stl

Rear half of the filter cell — the film sits in its recess

mak127_solar_filter_cell_front.stl

Front half, the one facing the Sun

mak127_solar_filter_dust_cap.stl

Magnetic dust cap for the front

mak127_solar_filter_tube_plug.stl

Plug for the tube mouth, so everything packs together for transport

mak127_solar_filter_film_template.stl

Tool — a flat template for tracing the film outline before cutting

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.