Yerkes Observatory | Operating the World’s Largest Refracting Telescope

Operating the 125-year-old Great Refractor telescope at Yerkes Observatory is no small feat. At 64 feet and 19 tons, the Great Refractor is so expertly balanced that it can be moved by hand. Find out how the Great Refractor works and learn more about the incredible history of Yerkes Observatory in Williams Bay, Wisconsin.
Photo Credit: Wikimedia Commons/Yerkes Observatory. Yerkes Messier 51 Canum Venaticorum 1902, G.W. Ritchey, Albert Einstein and Observatory staff in front of the 40-inch Refractor.
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Yerkes Observatory: yerkesobservat...

[@johnlary8792]

Correction - Einstein won the Nobel prize for his work on the photoelectric effect, more specifically "for his services to Theoretical Physics, and especially for his discovery of the law of the photoelectric effect".

[@tomc.7520]

Let me just say, thank you, to all the folks who are bringing this wonderful piece of astronomical history back to life and maintaining it. Your work really is appreciated by many of us astronomy lovers. Thank you Grainger for providing this video, have used your company many times.

[@davidskitt7994]

I toured and observed at Yerkes right before it closed. Very happy to see it is being restored for public use. My astronomy club has a 6.25 in, Hasting-Byrne refractor from 1879 that we still use for public outreach. It is very similar the the finder scope on the Great Refractor.

[@jameshorner242]

Awesome stuff !!! So glad and proud that this telescope is being brought back to life and being maintained.

[@CCRoselle]

As a long-time Grainger customer, it is extra nice that they helped with this project.

[@CaliforniaEBRDude]

Fascinating! I didn't know that the floor moved.

[@GereDJ2]

Hard to believe you moved that telescope by hand. Thank you, great tour. Lick Observatory near San Jose, California is the second largest refractor, completed in 1886-8. Einstein also went to see the solar observatory atop Mt. Wilson in Los Angeles.

[@rexoravec]

Fascinating video and story! I noticed that in the photograph 2:41 of Einstein at the Yerkes Observatory on May 6, 1921, the telescope looks very much different than it does today in this video. In the 1921 photograph, the exterior of the telescope appears to have a dark matte finish, and there are at least six long shafts with handwheels running the length of the telescope. The eyepiece end of the telescope also has an additional apparatus that is separated from the main telescope by about a three-foot space. I read that this telescope is in the process of being restored as close to its original glory as possible. I hope that after restoring it to a period-correct condition, it will look just like how it was when Einstein first saw it.

[@2gameplan]

What an incredible labor of love.

[@PC-Phobic-Jean-Rene]

Interesting, How far has astronomical instruments advanced? Go to the Extremely Large Telescope, once completed, and wonder at the engineering technological progress, Yerkes far-surpassed. Being in love with astronomy since I was a boy, seeing that old classical telescope, still does something positive to me. Great optical instruments for long night-sessions, alone with the stars, studying the glorious heavens! One of the greatest jobs or occupations in the World.

[@dankoppel6271]

Regrettably, Einstein never won a Nobel prize for General Relativity (as he should have). His Nobel was for the photo-electric effect.

[@robertsonsid]

Finder scope has a finder scope!

[@Rotceh-r4g]

Great video. Magnificent refractor!!! Good to see no GO TO with it. 😊

[@RedHuntsman]

Beautiful scope and building. However the downfall of that facility was its location. Too high of latitude to study the rich southern objects in the sky. Light pollution from Chicago again hurt viewing southern objects, the percentage of nights with cloud cover, and the lack of atmospheric stability. Even at the time of this observatory's construction, there were those built in high altitudes such as the Lowell Observatory in Flagstaff, AZ where Pluto was discovered.

[@samfromportadown]

If a whimsical billionaire with more money than they knew what to do with wanted to, they could buy the observatory, have the building and dome dismantled brick by brick, have the telescope and its mount dismantled, and have all of it transported to a Bortle 1 location somewhere in the high desert of the California/Arizona/Utah/Nevada region, then have the building rebuilt and the telescope and mount reinstalled there.

[@mogret7451]

Amazing 😮😮

[@samschmit7181]

I wish I could afford to visit.

[@BCSchmerker]

+wwgraingerinc *Thanks for the briefing video.* Running an observatory is irreducibly complex by nature; one must align telescope and roof aperture, raise an observation lift to appropriate height.

[@mdsaber7698]

wow❤❤

[@radioparisment628]

That's what I want, Apo fluo of course ! 😊

[@edfort5704]

Most big observatory refractors are achromats though.

[@joetuktyyuktuk8635]

Galileo would have been in awe to see this setup...

[@skisgy]

Awe inspiring! Einstein

[@ff_user]

NatGeo April 2024 issue brought me here. 😁

[@martinjcamp]

Very surprising on how much dirt can be seen in this video. I read elsewhere of a major ventilation upgrade to the station in the works. Hopefully that will help keep it much cleaner. 'Would love to go there sometime and see for myself!

[@TheLayinLo]

I want to apply for the job of cleaning. I’ll come sweep, mop, and dust if you’ll let me look through the telescope sometimes. I promise not to touch it unless I have permission.

[@Klaus-Schwab_Dictator]

Largest Refracting telescope in the world

[@oceanbreze1977]

What is the typical magnification power of this telescope?

[@brucea9871]

The magnification of a telescope is the focal length of the objective (the main lens or mirror in the telescope) divided by the focal length of the eyepiece. (The focal length is the distance from the main lens or mirror the light is brought to a focus.) So the magnification depends on the eyepiece used. I searched online and found the focal length of the objective lens on the Yerkes telescope is 19.4 metres. So if we use an eyepiece with a focal length of 2.5 cm (0.025 metres) the magnification would be 19.4 / 0.025 = 776. Nevertheless magnification is not the most important property of a telescope. The light gathering power (the ability to see faint objects) and the resolution (the ability to see fine detail) are more important. A small telescope may theoretically be able to magnify hundreds of times (if the telescope has a long focal length and you use a short focal length eyepiece) but small telescopes have low resolution so the image would be so blurry it would be useless. The larger the telescope the greater the light gathering power and the higher the resolution (assuming the telescope is of good optical quality). That is why astronomers want larger telescopes - not for higher magnification. In fact professional astronomers rarely look through telescope today. Instead they use sensitive cameras to record the images. Edit: I should add there is a practical upper limiting ito magnification due to Earth's atmosphere. Turbulence in the atmosphere often causes distortion in the image. Higher magnification amplifiers the distortion which places an upper limit on the useful magnification. Some telescopes today get around this problem by using adaptive optics. This system uses a deformable mirror whose shape can be altered up to 1000 times a second under computer control to correct for atmospheric turbulence.

[@fruitcup01]

​@@brucea9871Thanks, I think about 450 power is probably very good , and say 700 power is just slightly better , and if the objective is made larger.

[@gilles987654321]

Wonderful! Tks! Given this setup, how did astronomers track a DSO through the night? Manually (including rotating the open dome)? At least, I assume they were not bothered with Meridian flips...