Observatory 5: Yerkes, Part 3 – The Observing

Written at Sturtevant, WI, Amtrak Depot on Tuesday, August 14
As for the observing itself, the conditions were less than ideal. It was mostly clear and warm 78F at start, 70F at end. Humidity was predicted to be 70% or higher, which is pretty wet. Thin crescent moon (2 days old) was setting as I arrived. Well, it was low in the west. The sky was thick and hazy, and that was the big problem. High humidity, change from mostly cloudy to mostly clear, and apparently, smoke from the California wildfires all conspired against us. The seeing was muddy and rolling, with brief glimpses of clarity. I was really stunned, though, at my first look at Jupiter. Could hardly get a focus on it, and it was yellowish and dark. The color was from the smoke, acting like a filter. It was low in the sky, too, so that didn’t help – looking through a LOT of unstable air. So the image was very large (because of aforementioned optics) but very distorted. It was hard to make out the North and South Equatorial Bands even. Second time viewing was a little better. Could make out the bands and some occasional details between and a bit of darkening near one of the poles (not sure which it was). Still, I’ve seen better with my 90mm scope at home. So yeah, that was a huge disappointment.


Things improved slightly over the evening , but I was frustrated that with 40” of glass to work with here, I consistently have had better views at home. That is the way astronomy goes, though, AND that is perhaps one of the reasons Yerkes is a museum piece more than a research scope these days. Too many nights of weather-degraded viewing a year. Anyhoo,…


Saturn was in much the same boat as Jupiter, only a bit higher. The Cassini Gap in the rings was mostly visible most of the time. With patience and a couple turns I could see disk shadow on the rings behind. A little bit of color distinction on the disk — gray at top, less so further down.
Sketch of Saturn from my journal.
M11 Wild Duck Cluster – Even this was underwhelming. Nice full view of the cluster, but I felt like the stars weren’t quite in focus. We could run the focus in and out, but it didn’t seem to make a lot of difference. By this time I was just accepting that the seeing was crap, and I should just relish the experience.
My hope rose again for M17 Swan/Omega Nebula, as nebulae are less affected by bad seeing, but the guys had a hard time even finding it! They added a filter to help. When I got my tern I saw the problem. At f/19 and 475x, we were looking at a tiny portion of the nebula. It served to show noobs what a reflection nebula looks like, but it was like looking at the Mona Lisa’s neck. In fact, we were looking at the neck of the swan, I think. It’s one of my favorite Messier objects, so I think I recognized a pair of stars in the field. Looked like:
Sketch of M17, the Swan Nebula, from my journal

which is cool, but at low power it looks like a swan.

[Here’s a picture I found of what we might have been looking at.]

M27 Dumbbell Nebula – Again, the planetary nebula suffered from narrow field of view and high magnification. It was clearly visible but took up most of the field of view, so there was no sense of scale or contrast. I would have backed off the magnification a bit, but I don’t know where you get an eyepiece longer than 40 mm.

The last object for the night was M2, a globular cluster. This one actually looked good! It was a nice fit in the field of view, and the resolution was good, too. Still felt like it could have had sharper focus, but it was okay. Bright core and grainy cover and pretty even drop off out to the edge. (Yeah, well, I know what I mean.) Really a lovely object, or couple hundred thousand objects, as it were.

Sketch of globular cluster M2 from my journal.

And that was that. They brought the lights up and a bunch of us took pics. I got someone to take a couple of me, one looking at the camera and one looking into the telescope eyepiece. The second was stupid, of course, as (1) the lights were on (2) the dome was closed (3) the scope was no longer even pointed at the shutters. Oh well. The first one is a good picture.

The evening ended pretty unceremoniously.

I stood outside for a little bit, letting my eyes readjust to see what the sky looked like. Pretty much like ours at home, I guess. I hoped to see a meteor before going and pretended I did. It was midnight, and I had an hour to go after a long day, so I hit the road.

4 thoughts on “Observatory 5: Yerkes, Part 3 – The Observing

    1. Ah, but this IS my viewing through the 40 inch scope! I guess I didn’t say that in the post as it’s a continuation of what I wrote in my journal.


      1. Right – I knew that. I just didn’t have time to read it when I saw it. I won’t ever get the chance to view through the 40-inch, since it sounds like the whole thing is coming down. Sorry you had an (atmospherically) bumpy night! But I learned much about viewing through a super-sized refracting telescope from your report. Thanks for posting it!


  1. Oh, gotcha! I hope they find a way to keep Yerkes open. It is an amazing place, a remarkable instrument, and a great outreach tool. If not, they do observing nights at Mount Wilson on the 60″ and 100″ reflectors. Now THAT would be cool!

    Liked by 1 person

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