Visual Observing With The 40-Inch Yerkes Refractor
September 2009 :
With it’s incredible 40-inch refractor, Yerkes Observatory in Williams Bay Wisconsin has long been on my list of “those places that I’d love to visit, but just haven’t been able to make it to yet.”
At the end of September 2009, I and Dan Lorraine, Jack Szelka, Joe Sarandrea, Jim Hendrickson, Glenn Jackson and John Briggs of The Skyscrapers Inc. amateur astronomy society of Rhode Island got the chance to not only visit Yerkes, but had the rare opportunity of a night of exclusive observing with the 40-inch.
If I’ve caught your interest, perhaps you’d like to know a bit about our trip and what the observing was like with such a unique and historic instrument.
Landing in the nearby city of Chicago, our intrepid group first visited the historic Adler Planetarium. If you’ve never been there, it’s a must see for anyone with an interest in astronomy.
Home to the Atwood Sphere, Chicago’s oldest Planetarium built in 1913, The Adler also houses many historic instruments and books and an historic Zeiss Planetarium Projector.
While we were at the Adler, we were fortunate to arrive during the time when there was a display of telescopes through the ages including an 1863 4 inch Alvan Clark refractor and the original wooden tube and mount from the 18 inch Dearborn Michigan refractor also made by Alvan Clark and Co. circa 1864. Since we were to shortly to visit the 40-inch also built by the Clark corporation, seeing some of it’s predecessors was a great way to whet our appetite for more.
While at the Adler, we were also treated to one of the more unusual, boy is this a small world type of coincidences that one could have in life.
In the bottom floor of the building, there was an exhibit devoted to cosmology. Contained within the exhibition, was an exact copy of a notebook that the Adler has in it’s possession that was once owned by Dr. Alan Guth. Dr. Guth is the cosmologist who proposed the theory of Cosmic Inflation now considered a part of the standard hot Big Bang theory of the creation of the universe. The notebook on exhibit contained his notes detailing his breakthrough calculations and notes on his insight into his theory.
Dr. Guth is on the faculty of M.I.T. not far from Rhode Island and we had him at one of our meetings in April of 2008 as a speaker so we were very familiar with him. The reason I mention this is that while we were perusing the cosmology exhibit, who should show up there, but none other than Dr. Guth himself! He was in town for the birthday party of a colleague. It felt like the Adler had a special button installed next to Dr. Guth’s notebook which if you pressed it would have Dr. Guth pop up out of the floor and talk about his theory for you. A truly amazing coincidence!
After this, we reluctantly left the Adler and made the 2 hour journey to Williams Bay in nearby Wisconsin. If you’ve never been to Yerkes, you should know that it is located in what is now a typical suburban type of area and not far from a local lake. The area is a mecca of tourist activity. Not where you’d expect to find your typical big time observatory!
No visit to Yerkes is complete without a tour of the outside because of the incredible ornate architecture. To do that, we had made prior arrangements with Richard Dreiser, director of public relations and tours, and an expert in the lore of the fabulous old building.
Yerkes is a terrific example of late 19th century construction. Every square inch seems to be taken up with a carving or ornamentation, many of which are astronomical in nature or faces of people involved with Yerkes or the University of Chicago which built it. No one knows for sure any longer what some of the carvings mean because, after the architect who designed the building died, all of his papers were burned and much of the history of the construction of the building was lost.
Inside the building there is lots of dark wood, ornate tile and more carvings as well as an incredible feeling that some of the famous astronomers of old who worked there are still roaming the halls longing for a telescope to look through again.
After a cloudy, overcast day, fortuitously the sky began to clear in the evening. The time had come to get down to business and spend some quality time with the 40-inch scope. The 40-inch isn’t used for public viewing. However, one of our society’s members who was along with us on the trip, John Briggs, had worked for 14 years at Yerkes and we were given unfettered access to that magnificent instrument. Nothing can really prepare you for the experience of seeing this immense telescope for the first time. To get to the dome housing the 40-inch, you first have to go from the main floor of Yerkes to a grand and imposing two story marble staircase truly fitting for such a historic instrument. You climb up all those marble stairs and finally pass through a large metal double door to a vast space beyond. The dome itself is 90 feet in diameter and the observing floor that can rise and fall with the motion of the telescope is covered with hardwood flooring and 75 feet across. The floor has a range of motion up and down of 23 feet and is controlled by a push button arrangement at the eyepiece end of the telescope. When you first enter the dome, it seems almost big enough that you expect to see occasional clouds up near the top of the dome. After getting over our first bout of shock and awe at seeing the enormous telescope tube, giant gears and setting circles all resting on a huge metal pedestal built like a battleship we got down to business.
Climbing up a set of stairs to the balcony near the skirt of the dome, John Briggs pushed some buttons on a control and we all watched as the 85 foot long double slit opening gracefully split apart to it’s widest extent providing an opening 13 feet across through which we would soon be pointing and actually viewing through the world’s largest refractor.
Here’s where things got really interesting. While the telescope is motorized, most of the work of moving it around to point it to different sky objects is actually done the old fashioned way. That is, pushing it around by hand, lining things up as close as possible with the giant setting circles and then using a 6 inch f/15 refractor finderscope to zero things in. It’s much the same way things were done a hundred years ago when the scope was young. There is no better way to get the feeling that you are in the dome with people like George Ellery Hale or E.E. Barnard who would have used and viewed through the scope.
A scope this big was surprisingly easy to move around, though there is a huge amount of momentum and inertia that you had to be aware of. If you push it fast enough and hold on, you can find yourself dangling 5 or 6 feet above the floor. Not that any of us did this of course. Well, all right John did this once just to show us. One of the unexpected things about observing with the 40-inch had to do with the elevated observing floor. To function well and not induce any vibrations, the floor has a bit of play and sways a bit after moving or when people are walking around on it. The best way that I can describe the sensation was being on a boat on the ocean with a small amount of wave action. Apparently one of the reasons that the public isn’t invited to observe with the 40-inch is that some people have actually become sick from this motion.
At the business end of the scope there is a rig used for taking photographic plates. To use it visually, John had to attach a special interface that allowed us to insert a 2 inch 55mm eyepiece that we had brought with us. Despite the fact that this was a 55mm, this turned out to be a perfect choice for an f/19, 40-inch scope and the things we viewed filled the field of view nicely.
So, what do astronomical objects look like through this famous old scope? Over the course of the 6 hours or so that we had access for viewing, we saw Jupiter, the Moon, M15, the Ring Nebula and the Saturn Nebula. I know that 5 things over a number of hours doesn’t seem like a lot, just keep in mind that changing from one object to another with a big scope like this takes time. Time to move the scope to the right places on the setting circles, time to center the objects, time to get the elevated floor to the right position and most important of all, time for everyone to get multiple views and tear themselves away from the eyepiece. Jupiter was amazing and appeared huge and detailed. Enough light is collected by such a large scope that when you put your hand just behind the eyepiece, you can see a bright image of Jupiter projected there. The Great Red Spot was easily visible near the meridian, many festoons and smaller ovals were seen and finally we were treated to a shadow of one of the moons on the planet followed by a transit across it’s face. Unfortunately, we didn’t have an ephemeris to let us know which moons were involved. The Galilean moons were large and had clear, distinct discs, though the seeing wasn’t good enough to see any detail on any of them.
In some ways, viewing the moon through such a scope was even more impressive. We were treated to awe inspiring views of the Appenine Mountain area, the Alpine valley and many craters and other details. The only disappointing part of seeing the moon through the 40-inch was the fact that by the time we got around to it, the moon was not too far from the horizon and the seeing wasn’t all that great. Following this, we turned the scope to the M15 globular cluster. Magnificent and resolved easily to the core with bright stars that appeared yellow in color to me.
Following this we turned to the Ring nebula. It almost filled the field of view! The most amazing thing about it was the color that we all saw. No longer just a round smoke ring, like in a smaller scope, it was much more oval shaped with a distinct light reddish coloration near the oval extensions and blue green throughout the rest. The central star was easily seen and the center area of the ring was not just lightly filled in, but bright and much more apparent than I had ever seen.
The most memorable view of the evening for me was the Saturn Nebula. This was a delight! Strongly glowing in a bright greenish blue, multiple shells were seen and the 2 so called antennae on either side were bright and distinct. Of all the objects seen, this is the one that looked most like the pictures that I’ve seen and responded very well to a large instrument like this.
Regretfully after this, we had to tear ourselves away from this magnificent place. A two hour drive back to Chicago was ahead of us and while it would have been nice to see even more wonders through this scope, none of us wanted to trade those views for the fatigue that would make the return trip unsafe. Not that any of us felt cheated in any way. A few hours spent with the ghosts of such famous astronomers as George Ellery Hale and Edward Emerson Barnard left us with wonderful memories that will last a life time.
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