The edge of the primary mirror of a Newtonian telescope creates strong halos around bright stars. The mirror holder pads create additional shadows in these halos. A primary mirror mask ring prevents, or at least reduces this effect.

I purchased a Wega primary mirror mask ring. It’s made of PLA, stable up to 110°C.

Gradually it would be very nice to own a 3D printer 😉

Update April 18, 2022

Comparison without and with the mask ring:

The halo is much softer than before. The shadows/obstructions in the remaining halo are produced by the focuser, which should be shortened, as mentioned by Matthias a few days ago.

The ring installation is relatively easy as shown below in 4 steps:

1 – Removing Primary Mirror Base

The primary mirror base has to removed from the tube.

It is held by 4 screws on the 130PDS.

I placed some scotch tape on the tube and the primary mirror base, simply to be able to install the base the same orientation as I removed it.

The mirror should not be touched! I blowed away dust or small particles with my dust-free air blower.

The 3 rubber pads aren’t fixing the mirror! They just secure the mirror from falling out, if the scope lies horizontally or for whatever reason vertically (primary mirror on top).

2 – Removing Rubber Pad Screws

The rubber pads have play since they don’t press against the mirror. Now is a good moment to take note of how loose they are attached and attach them the same way at the end!

I loosened the 6 screws which holds the rubber pads.

At this step I was very careful not to slip the screwdriver on the mirror surface!

I removed at least the screws and plates. The rubber pads can stay in place.

3 – Primary Mirror Ring Installation

I carefully attached the ring with all 6 screws without screwing them in to much.

I tightened each screw a little and always checked the play of the rubber pads.

The pads must have some play as originally. They may not press against the mirror, otherwise they can deform the primary mirror.

Originally there was a gap between the rubber pads and the mirror base. I tried to keep the same distance.

4 – Attaching Primary Mirror Base

Ready to install back the primary mirror base to the tube.

Before install the base back, I cleaned the mirror one more time. Again, I only used my dust-free air blower.

The original 3 top plates aren’t needed anymore, since the ring now takes over the function of the plates.

Mission accomplished 🙂

Most likely, collimation is now required!

I’m curious to see the difference in imaging… luckily I now have an image for future comparisons: M 101 Pinwheel Galaxy.

Now all I need is clear skies…

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