Last touched 2003 August 9
Originally published in spring, 2002, Amateur Astronomy Magazine
Everyone who sees my telescope has this comment: "That's a tall scope! Look at that ladder!" They are looking at TJ2, my homemade 20-inch f/6.4 dobsonian. Sometimes I think the 10-foot ladder I use to access the eyepiece gets more attention then the telescope. With a focal length of 134-inches, TJ2 is slightly longer than a 25-inch f/5 dobsonian.
When TJ was first built, we purchased a classic 10-foot wooden stepladder at the local hardware store. When we bought it, we set up every 10-foot ladder at the store and picked out the one that wobbled the least. Five years later, I picked up a Werner 10-foot aluminum stepladder. This ladder was your traditional four-legged beast, with steps 10-inches apart.
I normally dealt with the inherit instability of the four legs on uneven ground by stepping on the first rung, reaching up towards the top of the ladder, pulling back with my arms and weight so I would lift the other two feet off the ground and smack them into the ground. This would indent them into the ground - the old brute force approach.
Another pain of this ladder was that it always seemed the eyepiece was placed between two of the steps. One step would be too low, the other too high. I'd either have to stretch to see into the eyepiece, or I'd have to bend down. I had always meant to add half steps on this ladder, but never got around to it.
Sometimes, I was forced to setup TJ on a slight slope. The telescope handles this fine, but the ladder would often become dangerously unstable in certain positions.
Nonetheless, I was perfectly happy with the Werner ladder until two years ago when I used an 8-foot tripod "Orchard" ladder at a star party. These have three legs; two at the steps, one long pole for the support. As a kid, growing up in Ohio, I had used these ladders to pick Apples. The single leg would nicely squeeze in between the branches of the tree so you could reach the fruit.
Then, a few months ago, a fellow observer, John Nussbaum, asked a local email list if anyone was interested in ordering an "Astronomers" ladder from Tallman Ladders in Oregon and splitting the shipping costs. Having used an orchard ladder, I decided to blow my meager annual astro budget on this one purchase.
After looking over the Tallman website (http://www.tallmanladders.com/), I sent them an email to get a quote for a 10-foot astronomer ladder. They replied back $150 for the ladder, $120 for the shipping from Oregon to Maryland. The "Astronomers" ladder is the same as their standard Orchard ladder, but the steps are only 8-inches apart. These ladders are made entirely of aluminum.
John had managed to find a third buyer, so we split the reduced shipping at $60 for each of the three ladders. John placed the order.
Tallman makes the Astronomers ladders to order, so I wasn't expecting overnight shipping. Nonetheless, I was pleased when John emailed three weeks later that they had arrived.
Once home, the ladder was quickly set up and examined. Several things were quickly apparent. They weren't kidding about making them to order, you could even see the pencil marks where they measured out the distance between the steps on each of the legs. The long third leg looked like a standard 1 5/8th-inch OD aluminum tube; just like you would use on a truss dob. However, Tallman says this pole is tempered, so as to be stronger.
There is no brace between the steps and the third leg can be swung out to any angle (60-70 degrees is recommended). This provides additional flexibility. If the eyepiece still ends up between steps, I climb down, adjust the angle by a few degrees and the eyepiece is no longer between steps.
The construction is mostly riveted... few screws or bolts to work loose. Only the third leg is held on via bolts. I suspect that in daily orchard use, the third leg might get bent, so this allows real easy replacement.
The lower steps are doubled braced to the legs to increase stability. The steps are made from channel material that has had holes with raised edges punched out so to provide extra gripping surface. Tallman sells devices to allow users to re-punch these holes if the edges become worn.
My favorite detail? The date of manufacture is hand written on the bottom of the top step, likely by the person who assembled it.
While the tripod nature of this ladder makes it more stable then its four legged cousins, there are other reasons why the Tallman ladder is more stable. First, the base of the steps is almost twice as wide as the standard Werner ladder. This effectively solves the problem of setting the scope up on a slope. Where I used to have to lean into the slope to feel comfortable, or to avoid the feeling that I was about to tip over, the Tallman ladder is solid as a rock.
With the 10-foot ladder, this is achieved by a smooth curve to the step legs. From the photos on the Tallman website, the 8-foot model is similar. The 6-foot model has straight legs, but there are extensions that provide similar functionality.
Another reason for its stability is how it sits on the ground. The Tallman ladder is designed to be placed on soil and not concrete or asphalt surfaces. Instead of rubber feet, the aluminum legs are unguarded and sink into the ground when you stand on the ladder. Small aluminum stops insure that both sides only sink no more than 1.5-inches.
One thing noticed right away is the weight of these ladders. Since a single pole replaces almost half the ladder structure, the Tallman ladder is about two-thirds the weight of a similar conventional ladder.
But the real test would be observing - and the best test would be observing at a star party with lots of people climbing up and down the ladder.
At the 2002 Laurel Highlands Star Cruise, I had just such an opportunity. During the day, while people came by to look at my 20-inch scope, just as many were more interested in the ladder. A half dozen asked if they could climb it. Another half dozen expressed skepticism from the ground and had to be urged to try it out for themselves. Not one of these was disappointed. Three came back later and said they were scared of ladders until they used the Tallman. One person said they had purchased a short focal length mirror to avoid using a ladder and if they had known about the tripod ladder, they might have reconsidered.
After dark, as observers came over to look through the telescope, a general observation was on first use, they stumbled climbing up the ladder because of the 8-inch step separation. But usually by a second climb, they had adjusted and didn't have any problems. I don't notice the difference at all now and it will be interesting to see if I stumble the next time use a conventional ladder (I did).
If I have a complaint about the Tallman ladder, it is at that steps are too narrow, about half the width of the Werner ladder. Only time will tell, but I have noticed if I'm wearing sneakers, a long view at the eyepiece starts to introduce a bit of strain as a smaller part of my foot is supporting all of my body. This hasn't really been an issue and won't stop me from using it by a long shot.
I can only ask why haven't owners of large dobsonians been using tripod ladders en-mass before this? I don't know other then it has been too easy to run out to the local hardware store and pick something up and the availability of tripod ladders hasn't been widely known in the community.
An old axiom urges life is easier if you use the right tool for the right job. I've become convinced since the invention of the large dobsonian, we've tended to use the wrong ladder for the job. This has had a pretty noticeable impact on our hobby, especially in recent years.
On various large dobsonian mailing lists, I've seen many, many ATMs or Dobsonian buyers pick their aperture and focal ratio based around what they could use without a ladder because they didn't feel safe on a ladder. A glance at some large dobsonian manufacturers shows that some have tailored their product lines to this approach.
This has forced mirror makers into producing faster, shorter, more difficult and more expensive-to-produce mirrors.
The push, in recent years, for almost perfect optics has put tremendous strain on the mirror maker's abilities to produce both the fast and high quality optics modern amateurs demand. These fast telescopes require better collimation, resulting in many amateurs purchasing a collection of lasers and other collimating devices that they other wise might not need.
These short focal ratio telescopes require complex, highly corrected, shorter focal length, much more expensive eyepieces to achieve the same image scale as a longer focus instrument does with a longer focal length eyepiece that is cheaper, less complex and has fewer glass elements.
Finally, you'd think a long focus dobsonian with a tall ladder would be a poor choice to show the public views through a telescope. I've used TJ at many public events and have never been disappointed. Visitors have often come back for a second look at a planet, after looking through other large aperture, but short focus instruments. Why? I've asked. "This one is easier to look through" is a common response. I once heard John Dobson plea for ATM's to make long focus dobsonians because "Miss America can look through them with her glasses on." This refers to how I can use a longer focus eyepiece that has good eye relief when others are using short focus eyepieces that not only have short eye relief but are subject to the famous kidney bean effect.
Perhaps with the use the right ladder, more amateurs will be willing to use longer focal ratio telescopes that are more tolerant of collimation, easier to produce optics with just as high quality images at an overall lower price.
I suspect the Tallman Astronomers ladder is a step in the right direction.
Bob Bunge has been an amateur for 20 years. He has plenty experience with heights. Before using his 20-inch f/6.4 dobsonian, he used a 31-inch f/7 Newtonian.
Back to Bob's Homepage.