Question:
Is a design like this possible? Practical?
I have a very high fidelity paint image here. And on the left is what I believe reflector telescopes do with the light received.
On the right is what I’d see as possibly an alternative solution that will maybe eliminate the risk of donuts from the image? At the expense of reducing the speed of the telescope.
I’m assuming there’s a reason why the solution on the right is not done. It may simply be impossible to get the right mirror geometry to produce this “zig zag” light path folding pattern without distortion. Though I suspect that is not the case.
It may be that for astrophotography, with a fixed single, infinity focal length, the donut patterns are relatively easy to resolve and so it’s not worth the reduction in light capture or complexity of design.
It may be that calibrating and lining everything up would be too complicated.
Not sure but I’m curious what thoughts others have.
📷 image.png
Alternative reflector telescope design to eliminate diffraction patterns
Beats me. Why don’t you build one and find out?
Make something brand new. 😉
Ahkilleux · Mar 3, 2026, 11:54 PM
Question:
Is a design like this possible? Practical?
I have a very high fidelity paint image here. And on the left is what I believe reflector telescopes do with the light received.
On the right is what I’d see as possibly an alternative solution that will maybe eliminate the risk of donuts from the image? At the expense of reducing the speed of the telescope.
I’m assuming there’s a reason why the solution on the right is not done. It may simply be impossible to get the right mirror geometry to produce this “zig zag” light path folding pattern without distortion. Though I suspect that is not the case.
It may be that for astrophotography, with a fixed single, infinity focal length, the donut patterns are relatively easy to resolve and so it’s not worth the reduction in light capture or complexity of design.
It may be that calibrating and lining everything up would be too complicated.
Not sure but I’m curious what thoughts others have.
📷 image.png
You will only see donuts in the image from a reflector when it’s out of focus. You won’t see that when you are in focus. All the stars would be round with a gaussian distribution of intensity. You’re looking for a solution to a problem that doesn’t exist. Now if you’re asking about reducing diffraction spikes, that’s a different thing entirely.
Question:
Is a design like this possible? Practical?
I have a very high fidelity paint image here. And on the left is what I believe reflector telescopes do with the light received.
On the right is what I’d see as possibly an alternative solution that will maybe eliminate the risk of donuts from the image? At the expense of reducing the speed of the telescope.
I’m assuming there’s a reason why the solution on the right is not done. It may simply be impossible to get the right mirror geometry to produce this “zig zag” light path folding pattern without distortion. Though I suspect that is not the case.
It may be that for astrophotography, with a fixed single, infinity focal length, the donut patterns are relatively easy to resolve and so it’s not worth the reduction in light capture or complexity of design.
It may be that calibrating and lining everything up would be too complicated.
Not sure but I’m curious what thoughts others have.
📷 image.png
In a way it has been done, it is called a schiefsplieger or off-axis newtonian. It avoids having an obscuration of the exit pupil therefore avoiding the reduction in contrast at mid-frequencies in a typical newtonian design. Not easy to make at all and even less friendly in setting up and it is quite slow for all practical designs so good for visual but not so good for imaging.