 We're all well-familiar with mirrors. We use them in our everyday lives to make sure that we look good and perfect our style. And much like fashion can influence a generation, reflecting telescopes with their light-gathering mirrors have completely changed the way that we look at the cosmos. This is your space pod for May 15, 2015. The reflector is hands down the champion of modern astronomical research. We've even flown a few into space in multiple missions to look at completely different targets. Now the interesting thing about reflectors is that they have beginnings that they don't really need to be too humble about. Abu Ali Al-Hasin Ibn Al-Hasin Ibn Al-Haytham is considered the progenitor of the reflecting telescope. He was an 11th century polymath and one of the central figures in the Arab world scientific productivity occurring at that time. His writings in the book of optics propose the concept of mirrors as optical systems, especially the use of curved mirrors. We've got to leap ahead by about 600 years before any major progress is made. Scottish mathematician and astronomer James Gregory developed a proposal for the design of reflector telescopes in 1663. The guy you may have heard of by the name of Isaac Newton beat Gregory to actually building one, and the world's first Newtonian reflector saw first light in 1668. Gregory's design would see first light in 1672, but even with their development, reflectors didn't catch on initially. One of the issues affecting this in the practical world was the inability at that time of manufacturing techniques to develop mirrors of a high enough quality to actually allow the optics to work as designed. It wasn't until new techniques were developed in the 19th century that the reflector overcame its problems and exceeded the refractors ability. As has been mentioned before, a refractor is limited in just how big it can actually be, simply because the glass in the lenses can weigh too much. But reflectors, because they use mirrors, those can be built to thin specifications, meaning you can have a gigantic mirror that remains lightweight. Reflectors are slightly more complicated than refracting designs. Unlike the simplicity of a single lens, a reflector requires at least two mirrors placed at accurate distances apart from each other. In the majority of modern designs, the largest mirror is set at the bottom of the telescope's tube. We call this the primary mirror, because this mirror performs the light-gathering grunt work. The second mirror takes the light being reflected into it by the primary and bounces that light to your eyepiece. We call this the secondary mirror, and most are placed above the primary mirror. Reflectors are light buckets. They can soak up a huge amount of light as compared with a refractor of the same size, but one of the issues with them is that the secondary mirror is sitting above the primary mirror. This creates a problem in trying to produce ultra-precise imagery, but because of that ability to soak up light like a sponge, reflectors are considered to be the ideal choice for views of deep-sky objects such as nebulae and galaxies. Thanks for watching This Space Pod, I'm Jared Head. Don't forget to comment, subscribe, and donate to our Patreon campaign. Next week we'll be talking about catadioptric telescopes and how you can work with those weird ones. So, for This Space Pod, thanks for watching, and keep exploring.