27 replies to this topic

[dddhgg]

Has anyone ever looked through the old 40 inch refractor at Yerkes Observatory? What was it like?

Thank you!

[woodsman]

That would certainly be a thrill, now wouldn't it??

[L. Regira]

The only historical scope I viewed through was the 24 inch Lowell Observatory scope in Flagstaff, Arizona in 1987. My wife and I waited in line 90 minutes for a 30 second peek. It was aimed at Saturn when the rings were very open and the image was burned into my brain for many years thereafter. Saturn was beautifully placed on a black background with a few tiny moons visible.
Lawrence

[deSitter]

Has anyone ever looked through the old 40 inch refractor at Yerkes Observatory? What was it like?

Thank you!

Chances are - not very impressive. The bigger the size of an achromat, the longer the focal length has to be to get the chromatic aberration down to a reasonable level. Even for a 3" scope you need f/15 or so to more or less eliminate the color. A 5" at f/10 is just tolerable. For a 40" you'd need in excess of f/200 to get a decent view! The advantage these large scopes carried was in resolution and position measurements, which are independent more or less of how good the image looks.

-drl

[EJN]

Yes, I have on 3 occasions. One was an all-nighter
I was invited to in thanks for bringing my scope
for a summer program for high school students they
had there.

Chances are - not very impressive.

Chances are - very impressive. While one does not think of
a large long focus achromat as a deep-sky scope, nothing
could be further from the truth. M13 was resolved completely
to the core. It looked like you were INSIDE the cluster.
The lowest power eyepiece they had was a 55mm, which gave a
bit over 300 power. M81 was great, you could just make out
the spiral arms. On M104, the dust lane was so obvious
it was unreal, and the nucleus was a diffuse point sitting
on top of the dust lane.

But the real stunner was M51. Look at a Palomer Sky Survey
image of it, that is how it looked, but bigger. There were
knots and nebulae visible in the spiral arms. The view
had an almost unreal quality to it that no image can convey,
and is difficult to describe.

Jupiter had a big purple halo as you might expect, and
seeing was not good. Yet the contrast of the cloud
belts was tremendous, and the colors were obvious.

(I have seen Saturn and the moon in the 18.5" Clark
refractor at Dearborn observatory which is 12 miles
from me, and again, while there was considerable
false color, the contrast was excellent).

I might add that the finder on the 40 inch is a 5" or 6"
(I can't remember which now) f/15 Clark refractor, and that
had a nice fairly wide field of view with absolutely
pinpoint images. I spent a lot of time looking through that
while others were at the eyepiece of the 40".

I live 90 minutes from Yerkes, and it is now for sale
by the University of Chicago. If I had $15 million I'd buy
it and preserve it as is.

[deSitter]

Yes, I have on 3 occasions. One was an all-nighter
I was invited to in thanks for bringing my scope
for a summer program for high school students they
had there.

Chances are - not very impressive.

Chances are - very impressive. While one does not think of
a large long focus achromat as a deep-sky scope, nothing
could be further from the truth. M13 was resolved completely
to the core. It looked like you were INSIDE the cluster.
The lowest power eyepiece they had was a 55mm, which gave a
bit over 300 power. M81 was great, you could just make out
the spiral arms. On M104, the dust lane was so obvious
it was unreal, and the nucleus was a diffuse point sitting
on top of the dust lane.

But the real stunner was M51. Look at a Palomer Sky Survey
image of it, that is how it looked, but bigger. There were
knots and nebulae visible in the spiral arms. The view
had an almost unreal quality to it that no image can convey,
and is difficult to describe.

Jupiter had a big purple halo as you might expect, and
seeing was not good. Yet the contrast of the cloud
belts was tremendous, and the colors were obvious.

(I have seen Saturn and the moon in the 18.5" Clark
refractor at Dearborn observatory which is 12 miles
from me, and again, while there was considerable
false color, the contrast was excellent).

I might add that the finder on the 40 inch is a 5" or 6"
(I can't remember which now) f/15 Clark refractor, and that
had a nice fairly wide field of view with absolutely
pinpoint images. I spent a lot of time looking through that
while others were at the eyepiece of the 40".

I live 90 minutes from Yerkes, and it is now for sale
by the University of Chicago. If I had $15 million I'd buy
it and preserve it as is.

Well that's good to hear! I shouldn't be so cynical. Of course that telescope generated a huge amount of important science too.

-drl

[Dark_Sun]

I've been to Williams Bay twice, just to see the observatory and the telescope. They never mentioned public access to the scope at night. Yerkes is a real jewel, just the architecture is very impressive!

[Bonco]

EJN
Excellent post, I've always wanted to know what views this scope could offer. Just shows how important it is to keep the scope and observatory alive and well for the benefit of the public and historical perspective. Thanks, Bill N.

[trainsktg]

Has anyone ever looked through the old 40 inch refractor at Yerkes Observatory? What was it like?

Thank you!

Chances are - not very impressive. The bigger the size of an achromat, the longer the focal length has to be to get the chromatic aberration down to a reasonable level. Even for a 3" scope you need f/15 or so to more or less eliminate the color. A 5" at f/10 is just tolerable. For a 40" you'd need in excess of f/200 to get a decent view! The advantage these large scopes carried was in resolution and position measurements, which are independent more or less of how good the image looks.

-drl

Not so fast there. The optical properties of these giant refractors get extremely interesting the bigger they go. At first glance, it makes sense that the giant refractors would indeed be awash in the purple glow of mixed blue and red light, yielding horribly washed out views. In reality these colors are so far out of focus (many inches in fact), your eye will not detect them and much of the CA is in fact invisible. Yes there is still visible chromatic abberation, but its not nearly as bad as the bright purple halos visible in our smaller scopes, most of which are focusing at points within 1/50th of an inch of each other.

Slightly off topic, Clark was actually planning to build a 60" refractor, but he died before the project could get off the ground. In his expert opinion, the glass would have been able to support its own weight in spite of what detractors said. It would have been very interesting to see such a beast.

Keith

[Bonco]

Keith,
Never heard of the 60 inch idea. Too bad it wasn't built but honetly I think the 40 inch was truely at the end of refractor evolution. Especially when large reflectors started coming into vogue. The 100 inch Hooker scope and other large reflectors of the time surpassed what any large refractor could deliver in performance and practicability.
Cheers, Bill N.

[Rob Willett]

I have regular (well a couple of times a year) access to the 28" refractor at The Royal Observatory, Greenwich.

My astronomy club, Flamsteed, runs out of the National Maritime Museum to which the ROG belongs. As an observing site per se it's rubbish as it's central London, as a site of historical significance it's fantastic.

Anyway, we get access a couple of times a year (weather permitting). We've used it a couple of times though for the last few years, we've always had dodgy weather.

The quality of the glass is ok, though I think my TMB is better, what a small scope can't convey is the sense of scale, especially with a binoviewer and a pair of wide angle lenses (35mm). Scanning the moon is like the famous video where Apollo 11 (?) is descending down to the surface. You see so much more, it's great. You get a sense of size, of being close by. It is quite magical.

You can push the magnification up quite a lot but it is a 100 and something year old scope, we have made improvements in glass and coating production in that time.

Anyway, this is not strictly relevant to the question but I'd be interested in how my experience compares.

[Bob S]

A number of years ago the University of Chicago offered an evening at Yerkes (for a fee which included transportation from Chicago to Williams Bay) through their continuing education program. I went twice, and have to agree with EJN that the deep sky views were spectacular. Both times I was there, the electrical drive failed, and the telescope had to be slewed by hand. For all its bulk, the tube moved rather easily. There was also an attempt going on at the time to use adaptive optics with the 40", but I think that didn't go anywhere. The University decided to pull the plug. Light pollution also played a role in the disuse of the 40". There is a nearby dog racing track which refused to turn off its lights. They keep the lights on all night,apparently to let people know they're there, but made astronomical use of the telescope almost impossible. The track is not in Williams Bay, which has kept its lighting friendly to the observatory. Yerkes may still be open for Saturday daytime tours, but I haven't checked recently to see if they're still doing this.
Bob Schoenstene

[2manyscopes]

Has anyone ever looked through the old 40 inch refractor at Yerkes Observatory? What was it like?

Thank you!

I've never had a chance to look at the Yerkes refractor let alone through it but a friend here has a 41.25" f/3.9 Newt that will blow you away! Limiting magnitude is slightly better that 17. I try not to observe bright objects that are easily visible in my puny scopes for fear that I'll develop aperture fever! I do enjoy using it on faint fuzzies that are magnitude 12 and fainter.
Bill

[Dark_Sun]

A number of years ago the University of Chicago offered an evening at Yerkes (for a fee which included transportation from Chicago to Williams Bay) through their continuing education program. I went twice, and have to agree with EJN that the deep sky views were spectacular. Both times I was there, the electrical drive failed, and the telescope had to be slewed by hand. For all its bulk, the tube moved rather easily. There was also an attempt going on at the time to use adaptive optics with the 40", but I think that didn't go anywhere. The University decided to pull the plug. Light pollution also played a role in the disuse of the 40". There is a nearby dog racing track which refused to turn off its lights. They keep the lights on all night,apparently to let people know they're there, but made astronomical use of the telescope almost impossible. The track is not in Williams Bay, which has kept its lighting friendly to the observatory. Yerkes may still be open for Saturday daytime tours, but I haven't checked recently to see if they're still doing this.
Bob Schoenstene

Good news, the dog track folded up 2 years ago. I think the Saturday tours are still ongoing. The Lake Geneva area is a great place for a day trip!

[JohnG]

Great to hear the dog track went under. Lights like that near a historic observatory are criminal. I've never been to Yerkes, probably never will, but I hope this great telescope and architecture will be kept in the right hands. Perhaps the National Park Service should take it over for preservation.

JohnG

[Bob S]

Yes, great news about the dog track collapse. The attempt to buy Yerkes and change it into a housing development failed. Apparently the notion of another educational institution buying and using it has also not come to be. I hope it isn't just allowed to moulder away. The electrical system for the mount definitely needs an overhaul. There are several reflectors at Yerkes as well as the 40" refractor, I don't know if the University is using any of them.
As I remember, the 40" had a 6" Clark as a finder; there is no dew cap for the 40", one of the astronomers there about 10 years ago said they cleaned the objective by throwing a bucket of water at it and then wiping it off. The lens is not coated, as far as I know.
The architecture of the observatory is worth seeing in its own right. Cobb, the architect, put all sorts of details in the building; there is a face, presumably of Yerkes, with his nose being stung by a bee, apparently because Hale was always going to him for money.
Bob Schoenstene

[Napersky]

I never looked thru the Yerkes but visited it during the day once. It was the scope the US ARMY chose to image the moon for the Ranger project under Von Braun. Interestingly, the did not choose any of the larger Reflectors.

[rmollise]

Chances are - very impressive. While one does not think of
a large long focus achromat as a deep-sky scope,

Which is just what I've heard from everybody I've talked to, amateur or pro, who has used this wonderful old scope.

[Bonco]

My dreams have me viewing anything thru the 40 Inch. Just to see it on it's giant mount and in it's classic dome would thrill me. This observatory must be preserved. Let's hope it's maintained as a national treasure. Now for all those fearful of chromatic aberation, lets stop it down to a mere 30 inches and check out Jupiter and Saturn...A blue fringe wouldn't scare me away. What a great monument to the progession of optical technology.
Bill

[Clive Gibbons]

Yes, I have on 3 occasions. One was an all-nighter
I was invited to in thanks for bringing my scope
for a summer program for high school students they
had there.

Chances are - not very impressive.

Chances are - very impressive. While one does not think of
a large long focus achromat as a deep-sky scope, nothing
could be further from the truth. M13 was resolved completely
to the core. It looked like you were INSIDE the cluster.
The lowest power eyepiece they had was a 55mm, which gave a
bit over 300 power. M81 was great, you could just make out
the spiral arms. On M104, the dust lane was so obvious
it was unreal, and the nucleus was a diffuse point sitting
on top of the dust lane.

Thanks for your report about the 40"!

Here's another, which echos your favorable observations-
http://www.theskyscr...ontent5632.html

[EdTheEdge]

I am planning a vist there next month! Can't wait.

[Wes James]

You folks really should read the book "The Perfect Machine", by Ronald Florence. It is the story of the building of the 200" telescope at Palomar- but it covers the history of all the scopes/observatories that Hale built, including the Yerkes (Hale built the observatory). It is probably one of the 4 or 5 best books I have ever read, and I was very sad when I finished it. I didn't want the book to end. I've read all the books on the 200" scope and Hale, and this is the best. It is a story of what the engineering hurdles they had to overcome to build the scope, as the technology to do what they did- didn't exist when they started. It's an amazing read- and currently listed on Amazon for only $16.50.

[ngc2289]

Clark did make a 48" scope for the Czar of Russia. The scope was shipped to Russia just before the revolution. After many years of sitting in unopened crates the scope disappeared during WW2.

[refractory]

Yeah, Stalin was going to use it to watch Hitler from his study in the Kremlin. Wonder where the lens is? I'd buy that if they need cash over there, but only if it isn't damaged. Now mounting it....

Jess Tauber

[Jon Isaacs]

It is the story of the building of the 200" telescope at Palomar- ....

and currently listed on Amazon for only $16.50.

Are you saying that the 200 inch Hale is currently listed on Amazon for only $16.50?

I enjoyed the book as well, lots of good stories. I liked the story about the 48 inch Schmidt. And the amazing thing about the Hale 200 inch is that they did not go over budget even with all the delays and the war.

Jon