Telescopes

© Norman Sperling, August 21, 2012

For the first time in many years, I attended a major, many-night-long star party. Hundreds of amateur skywatchers set up their telescopes and auxiliaries for nights of dark-sky observing at the Oregon Star Party, east of Prineville.

Their standard array is far more advanced than I remember from 30 or 40 years ago.

It starts on a ground-cloth: a tarp or a sheet or a tablecloth. Some are thin carpeting. Light-colored carpeting would make it easier to find things in the dark. Decades ago we set up in grass, and wasted a lot of time hunting important little things we dropped.

The telescope and several auxiliaries now consume so much electricity that observers lug out a battery, such as a small car would use. Wires from the battery to the equipment are sometimes neatly tied, sometimes run hazardously wild. Sometimes the battery tucks under the scope, inside a tripod leg. Decades ago very few observers had separate batteries, some tapped their car batteries, and most didn't use any electricity.

Tote boxes and padded equipment safes often sport custom-cutouts for specific eyepieces, et al. Most sites had 2 or 3 boxes and some had more. Decades ago observers had a lot fewer eyepieces, and all of those were much smaller than today's huge, massive marvels. So one simple container was all anyone needed.

Almost every site has a folding table or 2. Portable tables have been reinvented, with many patterns and sizes available from discount stores and outdoor outfitters. Some have roll-up table tops. Since the tables carry little more than laptop computers, atlases, and notebooks, light-duty hardware is OK, verging on flimsy. Decades ago the few who brought tables used card tables. We spread atlases out on car hoods and trunks, which were more horizontal then.

Everyone uses folding chairs. These, too, have been reinvented in profuse variety. Decades ago the only types had a flip-down seat as can still be found in schools and churches, and plastic-webbed aluminum-tube lawn chairs.

Tall Dobsonians became popular in the 1970s, and used the teetery ladders of those times. Now far more common, they use newer ladders with safer, wide-splayed feet.

I saw a few "anti-gravity" chairs for binocular use and meteor watching. Decades ago we had plastic-webbed, aluminum-tube chaise lounges.

Everything is carefully folded or furled to fit their vehicle ... or, the vehicle is chosen because it can hold the owner's full set. I remember marveling at how much more a squarish van held than a conventional station wagon. Now, vehicles come in so many configurations that everyone can carry everything they want. A lot of RVs at the star party showed red-light and sealed-window customizations, so many people are very serious about this.

The 2012-era scope site sports a great deal more stuff than its predecessor. The scopes themselves cost a lot more, and so does all the other stuff, and their vehicles. But the expense and the bulk deliver images far surpassing those of olden times, and computer-processed electronic imaging vastly exceeds old film astrophotography. They get what they pay for.

© Norman Sperling, November 25, 2011
Part of a series on Educational Star Parties:
Star Parties Designed for Students (July 7, 2012)
7 Spectral Types in 1 Big Loop (April 15, 2012)
Trading Cards for Telescopes and Celestial Objects (September 20, 2012)

For decades, I have been proclaiming that focal ratio is one of the most important characteristics in choosing a telescope. Most authorities tout aperture instead. But none of us has ever conducted a true visual test, isolating the variables of focal ratio, aperture, and eyepieces.

I propose that 3 triplets of Newtonian telescopes be made to demonstrate the effects of focal ratio, aperture, and eyepiece. They can be used for classes and at star parties to teach about the properties of the telescopes themselves. Mount each triplet so that viewers can easily shift among all 3 eyepieces to instantly compare views.

The "focal ratio" triplet should consist of 3 telescopes, all with the same aperture and eyepiece. Make one f/5, another f/10, and another f/20. For this triplet, I think 3-inch (76 mm) apertures are best: even the f/20 would be a manageable 5 feet (1.52 m) long. Users will see that Jupiter looks best at f/20, and the Great Andromeda Galaxy best at f/5. Trying this battery of telescopes on the sky's enormous variety of targets will probably reveal very few objects that look best at f/10.

A second application of this same telescope set will use different eyepieces that all result in the same magnification: a long eyepiece on the long scope, a short eyepieces on the short scope, and a middling eyepiece on the middling scope. How different are the views of different targets?

The "aperture" triplet should consist of 3 telescopes, all with the same focal length (perhaps 4 feet = 1.22 m) and eyepiece. Make one 3 inches (76 mm) aperture, the second 6 inches (152 mm), and the third 12 inches (304 mm). Users may be surprised how much even the 3-inch shows.

The "eyepiece" triplet should consist of 3 identical middling telescopes, perhaps 4-inch (102 mm) f/8. Insert eyepieces of equal focal length but different optical designs (such as Huygens versus orthoscopic versus Nagler). A second application of this same telescope array will use eyepieces of equal design but different focal lengths (perhaps Plossls of 6 mm, 12 mm, and 25 mm ...).

Make each triplet so the scopes, and their eyepieces, can also swivel to allow 2, or even 3, different people to watch through one of the scopes at a time. This is because, perhaps once a decade, some sky event brings out throngs, and the host needs to move a whole lot of eyeballs through the scopes in minimal time.

These triplets could be built by amateur-telescope-making workshops, such as several clubs run, or perhaps by a veteran scope-maker. Most are quite small, only one is large. Try hard to hold all but one factor constant so they really test that single variable.

A whole metropolitan area probably needs only one set. Telescope triplets can be passed around among nearby colleges, astronomy clubs, planetaria, etc., to use at their classes, star parties, and member-events.

© Norman Sperling, January 15, 2011

A recommendation by Sky & Telescope magazine last month, following a [.pdf] review last July, rekindled an old glow. The Astroscan telescope - my first big project - was once again named one of the 3 best inexpensive telescopes ... 34 years after it was introduced!

I remember its development clearly.

It was meant to be a superior first telescope, and it is. It has also proven to be a superior second telescope: folks keep it after they graduate to something bigger, and use it for a quick session, and as a convenient portable. Because people keep their Astroscans, remarkably few are offered on the used market.

Robert Edmund was taking over Edmund Scientific Company leadership from his father Norman. Norm has enjoyed retirement in Florida ever since. Robert had studied business management and knew how to run a going concern in changing markets. His telescope line was not doing well. Telescope leadership belonged to Criterion, Unitron, Questar, and Celestron, and Edmund Scientific wanted to earn its way to the top tier. The Astroscan was his opening salvo.

Robert Edmund hired me as a consultant in 1975, when I was 28. I was planetarium director at a private school, an hour's drive north of Edmund's. I was young and unknown and had even rougher edges than now. My ideas were unconventional, and entirely untested in the market. I contributed to a lot of Edmund's smaller astronomy projects, too.

I had observed observers observing in amateur, public, and school settings, and discovered that some of the wisdom of my elders wasn't wisdom. Telescope setup took frustratingly long, mountings were clumsy and shaky with narrow pivot points and long overhangs, eyepieces were tough to squint through, and views were underwhelmingly faint and dull. To improve on those, I preferred quick setup with minimal moving parts, stubby bodies, wide fields of view with wide exit pupils and bright contrast, lightweight and cheap. Those all shouted "Rich-Field".

Dr. Harvey Davis of the Lansing Astronomical Society introduced me to the principles of rich-field telescopes in the late 1960s. He was a friendly young math prof at Michigan State, where I was an undergrad. In the early '70s my friend - everybody's friend - Roger Tuthill made an RFT with an optical window (the success of which spurred us to do the same with the Astroscan). Roger's scope had a conventional cylindrical tube with a simple handle, so the only characteristics in which it was a predecessor of the Astroscan were the window and being an RFT. It didn't sell well at all.

No one in all history had ever gotten Americans to buy a LOW-power telescope, and we knew this was a huge hurdle. I assured Edmund that the telescope would please its users, but I explicitly never promised that anyone would buy it, and I wondered whether the expensive project would ever turn a profit. When Marketing VP Jack Sharff claimed that people would buy it, I thought that was bravado more than business sense. Sharff assured me that making it "popular" was his task, not mine. A good thing, because I understood almost nothing about marketing back then.

I wanted to make the eyepiece's exit-pupil an enormous 6 mm, because that's about the widest a dark-adapted human eye can take in. So, figuring from that, I championed a 4 1/4" f/4 (which the company nudged to f/4.2 for manufacturing convenience). Astroscan's richfield view - 3 degrees wide - means that finding things is easy, and keeping them in view is easy. It also means that hundreds of deep-sky objects are unusually contrasty, making them more obvious to beginners. The tradeoffs are minor: no astrophotography (which we wouldn't wish on novices anyway), planets look too tiny, and only a few double stars would look good. But any novice scope would only show pleasing detail on Jupiter and Saturn, the other planets being too small, featureless, and/or faint. So we swapped decent views of 2 objects (Jupiter and Saturn) to get superior views of hundreds of deep-sky objects.

I expounded on telescope design, exit pupils, and surface brightness in "Of Pupils and Brightness", Griffith Observer, January 1985.

At least as important as the optics, I wrote Astroscan's behavioral specifications. I remember blathering on and on for maybe 2/3 of a page singlespaced that I could have shortened enormously had I known the term "user-friendly". I didn't have the term, but I did have the concept. In beginner telescopes, it meant minimizing adjustments to fiddle with, and shortening the setup time (competitors, then and now, often take 15-20 minutes). Our setup time target was 3 minutes. We got it down to 10 seconds, and NO user's attention-span is too short for that.

While I did the optical and behavioral design, a brilliant young optical engineer, Mike Simmons, created the mechanical design that satisfied our needs. Simmons figured out that pushing the tube into the mounting made sense, and Simmons figured out that the ball-in-socket would work best. He was right. He advocated a very large sphere, with just the focuser-end of the tube sticking out. However, manufacturability, aesthetic appearance, and the awkwardness of a large-diameter sphere pointed the company to a smaller sphere, with more of the cylinder sticking out. This, however, is top-heavy, so to balance it, 2 semicircular slugs of cast iron surround the mirror. The extra weight, and the need for it, offended Simmons, and he left Edmund's soon after. I haven't seen him since the early '80s.

The shell satisfied all my specifications, including being nearly student-proof (it's meant to be checked out by students and carried home on a school bus). An industrial designer did the detail work. It's cast in 2 pieces of ABS plastic (one with the focuser insert, one without) and glued together.

In the fall of 1976, just before the first ads came out, I asked Robert Edmund what amount of sales he'd consider successful. He said 800 units by Christmas. Privately I thought that unlikely. Well, they sold 3,000 Astroscans in those first 3 months, which taught me another business lesson: there are DISeconomies of scale, as well as economies of scale. For example, the company couldn't produce the telescopes fast enough, and had to add shifts. Part of the optical design was meant to use an excellent, but slow-selling eyepiece that Edmund had a thousand of. They ran out, and had to scramble, buying every eyepiece on the world market that could possibly work - some Astroscans were shipped with Clave Plossls worth almost as much as the entire scope! Robert Edmund soon had Penn State's Dr. David Rank design the RKE eyepiece line, stimulated by the need to make a new eyepiece for the Astroscan. I'm happy that the company has sold in the neighborhood of 100,000 of them.

It was Robert Edmund who selected and hired and coordinated all the various people whose work combined to make Astroscan a success. He paid for all the work and assumed all the risk. He paid me quite well. In addition, the Edmund family and company ALWAYS treated me exceptionally well, and very often did me favors far beyond a conventional business relationship. Then and now, I regard my relationship with Edmund as one of the best I have ever had. I consulted for them for 9 years, 1975-84, but I have been a customer of theirs for 50 years, and endorse them as a fine set of people.

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Nobody since then has hired me to design a telescope, and such a project is beyond my personal resources. But I still get ideas.

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Parts of this post appeared on the Old Scope list in February 2002.