Newtonian Mask

[oopfan]

Throughout time and space, I've only owned refractors. In my opinion, refractors are great for lunar and planetary imaging, but I have also seen outstanding images taken by fast refractors, although they are pricey. Lately, I have become smitten by reflectors, although I do not own one (yet). One thing I like is the diffraction pattern produced by the secondary mirror assembly. So, until one day in the future when I decide to buy, I wanted to see if I could simulate it using my refractor. I watched YouTube videos where people use dental floss stretched across the dew shield, but I wasn't too happy with the results. So, I decided to create my own using my 3D printer.

The first attachment shows a 3D model of the profile of a secondary mirror and vanes, plus some imitation screws that add spice to the diffraction pattern. I created it using AutoDesk's Fusion 360. The next attachment shows the mask inside my flat-field device, something I call "The Flatinator." I built it two years ago from a concept I had. In the image, you can see the mask. It is held in there firmly by the surrounding structure, but there is still enough margin that I can rotate it to achieve any desired rotation angle.

I tested it two nights ago on the star, Almach, in Andromeda. It looks pretty spicy! Now I need to try it on a real target. Please see my upcoming posts in the Gallery for M34 and NGC 1664.

Brian

Newtonian Mask 3D Model.jpg (58.65 KiB) Viewed 353 times

Newtonian Mask Flatinator.jpg (35.47 KiB) Viewed 353 times

Almach using Newtonian Mask.jpg (18.79 KiB) Viewed 353 times

[admin]

Hi Brian,

that looks like an interesting project - all the fun of Newt star spikes and none of the high maintenance normally required by anything with mirrors

Did you find/use the 'Maskulator' program to simulate the pattern that you get from the mask before making it?

cheers,

Robin

[oopfan]

Robin,

I discovered that StarTools has a tool name "Synth". I talked about it briefly here:
viewtopic.php?f=16&t=3291

There are two steps involved:
1. Designing the "mask" with close to a dozen properties.
2. Applying the mask with a different set of controls.

It opened my eyes. I'll look into the Maskulator. Thanks!

Brian