About QuInsight and Spectre

The QuInsight and Spectre were developed with the idea that 3D printing enables delivery of high performance optics for the amateur astronomer at a competitive price.

In 2017, at the Total Solar Eclipse Oregon Star Party of August 20, my son Quinn was having trouble using his reflex sight because it made him bend over too far to get his eye aligned with a tiny field of view in a tiny lens while trying to look up at the sky . He wanted to know if there was something that could be done to improve upon the technology, and he had a good idea of what he wanted:

  • Move the pupil up high on the tube: No more extreme bending over on his 8″ F/5 to get under the combiner to see the image.
  • Large field of view: This would enable capturing the image long before getting perfect alignment between eye and lens.
  • Large lens: Perfect alignment between eye and lens is a thing of the past.
  • Easy to use alignment knobs: Make them move the reticle left/right and up/down instead of along on of three axes oriented at 120 degrees from the others.
  • An on/off switch that doesn’t click out of the off position if you’re not careful putting the device back in storage. No more dead batteries after one use.

To his list I added a rotating reticle with crosshairs, enhancing the “pattern matching” method of finding objects by aligning the features in the reticle to easy-to-see stars (even more powerful with the large field of view!) After working out some optical design studies we realized all of these features in a relatively simple design that could be 3D printed and assembled from off-the-shelf optical and electronic components at a competitive price.

The 3D printed parts are made using PETG, which is a very strong and thermally stable material relative to the commonly used PLA. No, not as strong as injection-molded polycarbonate, but at this early phase of development and product launch, injection molding is prohibitively expensive. Furthermore, the strength of the QuInsight has proven itself with a few dozen users and growing (as of Dec 2021) and over 3 years of development and beta testing. Of course, with 3D printing the design has evolved dramatically with very little investment, and as a result I am able to offer a quality product at about the cost of a Plossl eyepiece.

Spectre Spectroscope

Spectrum of Rasalgethi

During the dramatic and surprising “fainting” of Betelgeuse in Winter 2019/2020 a friend of mine showed me a “before and during” sketch of the spectrum that he made using a grating in his eyepiece. It was stunning, and I knew I had to have my own eyepiece spectroscope. But I also knew I would not be satisfied with a low-resolution spectrum since I have the equipment and know-how to make my own holographic gratings (a consequence of a lifetime pursuit of optics in the field of head-up displays).

Gratings bend light very strongly relative to glass and with more power to separate the colors from each other (dispersion.) Even so, a very large bend angle is needed to get the colors to separate adequately, and this causes spectrometers to have some very unusual geometries such that it is rare to see the spectrum come out on the axis the light went in as it entered the spectroscope. This isn’t really a problem for an expensive observatory-grade instrument with a camera, but it sure makes things difficult if you actually want to observe the spectrum with your eyeball in its full natural and beautiful color while resolving detailed absorption lines.

As it turns out there is such a design that makes the spectrum come out the way the starlight went in, and the University of Iowa recently published a paper on it: (http://astro.physics.uiowa.edu/iro/research_projects/grism-ajp-jan03.pdf) This gave me the answer I needed to implement my own design. I was able to simplify their design a bit (uses only one prism, not two) and put in some nice tweaks of my own. The first iteration of Spectre was built before Betelgeuse had begun to brighten again, and again I was stunned!

But this time I was stunned not only by the general “weirdness” of its spectrum as compared to the Sun, but also by the awesome detail that was impossible for my friend to sketch months earlier! Suddenly the stars had become objects of intense interest and beauty. As I pointed my 12.5″ F/5 scope to as many bright stars as I could I found that each had its own personality…but of course! Astronomers study the stars not just through their images, but also (and mostly!) through their spectra! The spectrum of a star is the code onto which is imprinted the star’s composition and autobiography, and even its future fortune.

-Rob Brown
Portland, Oregon, USA
June 19, 2020