3 unique elements in the design of the Soleye 300

Now that our website is live, and our first telescope is up for sale, we can celebrate a bit and share some interesting details with you. 

There have been a lot of decision points while designing the telescope and some unique challenges to overcome. Take a look at this short video to see all the versions of the Soleye 300, from 2017 to 2024:


The possibilities are, of course, virtually limitless. This is why the 300 is only the first in the line of innovative solar photography telescopes. (We'll share some updates about the next designs later this year.)

So, what are some unique features of the Soleye 300, and why are they the way they are? Let me give you a quick tour!

1. The Main Frame is lightweight and easy to use thanks to its bold geometry

If you are new to solar photography and haven't seen many telescopes used in this field, let me tell you: our design is totally unique. None of the other scopes look this way.

How are they different, and why?

Astronomical telescopes have had their grid structure for almost a hundred years now. There is a very strong cube in the centre of them, locked in place by a ring with a rectangular shape. Towards both directions, a 4-armed triangle grid extends. 

This solution is called the 'Serruier truss', named after Mark U. Serruier, and it makes sure that the frame is as inflexible as possible, meaning that when we move it in any way, both ends bend in the same direction. This is how the two main optical elements can stay collimated, i.e. perfectly parallel.


A classic example of a Serrurier truss (solar) telescope: a huge cube in the center, four triangular extensions in both directions

The Soleye 300 has no cube in the middle, though. And instead of four, there are only three sides reaching towards the top and the bottom. And we've made this work with a single ring instead of two.


A simplified presentation of the Soleye 300 core geometry

The implications of this are huge!

The overall weight dropped to 13 kilograms (the one you see in the image is 20 kilograms, so we shredded 30% of 'fat' already).

This makes the telescope light enough for most mid-class portable EQ mounts.

One key solution enabling this design is the railing on the side. This holds it firm enough when attached to the platter of the support structure. This is only possible because the railing connects the two rings with an expansion joint, allowing for thermal movement but still keeping it firmly in place.


A close-up of the lower part of the Soleye 300: the central vertical plate is connected to the triangular frame and the lower ring with an expansion joint. 

2. The Focuser sits tightly within the rods and in line with the railing

Traditionally, the focuser is held by two rings from both sides. 

Now, how can we get rid of this? Do we really need both of them? Feels inelegant.

Looking at the development sequence, you might have noticed that, at one point, we've had the camera mounted on top, but after a while, it goes back to the side. This is because we've had an extreme theory: we wanted to get rid of the secondary mirror altogether, placing the camera right across the primary. That would have been radically elegant, but of course, there's a reason why the secondary exists. With that layout, the focuser had an adverse effect on the light path. Moreover, the wiring and the heat of the camera cause turbulence right where the light is coming into the telescope - and as you probably know, turbulent air is the great enemy in solar photography; we're trying to minimise it, so having a source for it attached on the frame will never sound like a great idea.

This meant that the focuser went back to the side, but we put it in the plane of the railing for optimal weight distribution. All the mass is balanced as it is lined up on the axis.

We pulled the rods apart a bit so the focuser fit in between them nicely. This is why we use the Primalucelab Esatto2, which is a robotic focuser with a remote control, allowing us to fit it in there.

SOLEYE – 10 – photo Bánhegyesy Antal

Primalucelab robotic focuser between the rods.

3. The 'Air Knife' - a highly specialised solution for holding the primary mirror

I'm lucky enough to say that I belong to a group of astrophotographers who take their craft very seriously. Iván Éder, a pioneering, world-leading deep sky photographer, had already developed an ingenious solution for the primary mirror a decade ago. We based our design on his, adapting it to the parameters of solar photography requirements.

The key challenge with the primary mirror is that we need to hold it tight, although the framing around it expands and shrinks as it heats up and cools down. Otherwise, the mirror surface will be distorted and degrades optical quality.

The hooks sit on engineered casters, enabling the mirror to move freely when the air temperature around it causes it to expand a bit. This is known as a self-adjusting primary mirror cell, which helps the mirror assume the optimal position independently without obstruction or assistance.


The light and rigid self-adjusting primary mirror cell

We based our design on this. For our telescope, a bit more delicate solution was needed to minimise light scatter. But the original idea is the same: this setup is supported by vertical forces exclusively. 

The 'air knife' is engineered so that once you stabilise the telescope, the mirror finds its place and sits completely motionless. Infinitely loose but infinitely stable. 

A solution like this needs some assembly work; you can't just etch it out from a plate because the heat gets stuck between the mirror and the cell.

You also want to avoid anything reaching over the mirror, which could cause turbulence with any air movement.

Sounds like an easy and straightforward solution, right? It sure is. It only took us three years of research, development and experimentation to finalise it…

At Soleye, we are not settling for the existing manufactured opportunities: we are looking for inefficiencies and room for improvement that custom-made solutions could provide - and then we deliver them. 

The many innovative solutions of the Soleye 300 are the first package of results from this ongoing research and experimentation, a new horizon in solar photography with previously unexplored opportunities and capabilities.

Exciting times!