Alt-Az Initiative


Alt-AZ Initiative
Telescope & Instrument Developments
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Small Research Telescope Challenge
Undergraduate Student Research and Telescope Development


The Alt-Az Initiative is a catalyst for the development of low cost, lightweight, modest aperture (2 meters and less) alt-az research telescopes. Such telescopes, especially when automated and networked, can be cost-effective tools for dedicated research programs including low and high resolution fiber-fed spectroscopy as well as optical, near infrared, and high speed photometry. To date, two full conferences and twelve workshops have been completed. Twelve technical initiatives have been completed or are underway. These include optical designs, lightweight mirrors, active primary mirror controls, and direct drive motors and controllers. One low cost, lightweight, technical demonstration telescope with lightweight mirrors, a lightweight structure, and direct drives has been completed.  Future technical initiatives and technical demonstration telescopes are outlined. Two books, Small Telescope and Astronomical Research and The Alt-Az Initiative: Telescope, Mirror, and Engineering Developments,  based on these meetings, initiatives, and the demonstration telescope, are now available.

Small Research Telescope Challenge

Small Research Telescopes

Their Enduring Value: In the age of giant telescopes, are small telescopes still useful?  Weaver (2003) points out that  

Both quantitative and qualitative arguments demonstrate the continuing importance of small telescopes to the astronomical endeavor. The quantitative arguments show that it is significantly less expensive per citation to use the smallest telescope that will accomplish the research.  Both the quantitative and qualitative arguments show that the research accomplished by small telescopes is of continuing and lasting significance to the discipline as witnessed by their non-diminishing contribution to astronomy over the last century and the persistence of their citation histories. 

Ringwald et al (2003) suggests that 

Small telescopes can hold their own with larger instruments since more time is available on them. This makes possible monitoring campaigns, aerial surveys, and time-resolved campaigns, particularly if the telescopes are networked or automated—all difficult to carry out with larger telescopes, for which even small amounts of telescope time are in great demand. 

The 2007 report of the Committee for Renewing Small Telescopes for Astronomical Research (ReSTAR) concluded that 

The science to be done with small and mid-size telescopes remains compelling and competitive in the era of big telescopes. Small and mid-size telescopes continue to produce innovative science in themselves, and to provide precursor and follow up observations that enhance the scientific productivity of larger telescopes.  Small and mid-size telescopes also enable scientific investigations that are not possible on larger telescopes.

The ReSTAR report went on to state that 

Small and mid-size telescopes contribute additionally to the discipline through their training and educational functions and as test beds for innovative new instrumentation and techniques.   

The Challenge

Increasing Participation through Greater Affordability

Weaver (2003) recalls that 

Astronomy has a history of an essential synergy between small and large telescopes.  This synergy can be maintained only if there is a reasonable number of well-maintained, well-instrumented smaller-sized telescopes. 

Budget realities suggest, however, that both national and large-institution funding of expensive to build and operate but vital cutting edge large telescopes will make it difficult to also fund smaller telescopes in sufficient numbers to maintain an optimal balance between large and small telescopes.  Further, during hard economic times, it will also be increasingly difficult for smaller institutions to fund small research telescopes themselves. So what is to be done?  How can we maintain the balance and the synergy between large and small telescopes? 

Meeting the Challenge

Lowering Costs through Advanced Technology and Quantity Production 

In his book, Excursions in Astronomical Optics, Lawrence Mertz (1996), after noting that there is a “crying need for more observational facilities to outfit the throngs of young astronomers,” offered a solution: 

The remedy, it seems to me, would be a proliferation of modest-sized telescopes in the 1.5- to -2-meter class that are sufficiently standardized for economy. The size is large enough to accomplish significant work, yet is small enough to become affordable if the design were standardized. All too frequently small institutions insist upon designing their own telescopes almost from scratch to fulfill their individual tastes.  It should be evident that that course is hopelessly uneconomical, just as it would be uneconomical for each automobile to be custom designed. In essence, what is needed for observational astronomy is numerous … relatively inexpensive telescopes in the 1.5- to 2-meter class.  Even at this modest size there does not remain much question between altitude-azimuth (alt-az) and equatorial mounting; computers now make the former more economical. Alt-az has the further advantage of simplifying the primary mirror support since tilting is restricted to the elevation axis. 

We can expand on two of Mertz’s vital points. First, advances in technology, especially in computers and electronics—but also materials and other areas—can reduce telescope costs.  Mertz illustrated this with an obvious example—shifting from equatorial to alt-az mounts. Second, true economy can only be achieved through quantity production. “One-off” telescopes will always be expensive. Although Mertz did not mention it, a third point could also have been made:  large “one-off” telescopes with their sizeable development budgets often pioneer the new technologies which subsequently migrate to small production telescopes. These “tech transfers” are completed once clever ways are devised to drastically reduce costs so that the large telescope technologically-inspired breakthroughs can be incorporated economically into small telescopes in quantity production. 

Two Telescope Tech Transfer Examples 

Consider, as the first tech transfer example, alt-az telescopes themselves.  The 5-meter Hale telescope, completed over a half century ago, remains the largest equatorial telescope ever built. There are now over 20 larger telescopes.  Every single one is alt-az.  Smaller telescopes are also heading down this same evolutionary pathway. 

Until recently, most truly small (less than 1 meter) telescopes remained equatorial because alt-azimuth telescopes not only required constantly changing drive rates in both altitude and azimuth, but to avoid image smearing also required a field de-rotator—a significant complication. However, these complications did not apply to visual-only, manually operated, non-tracking alt-az telescopes. In their search for larger apertures at low cost, Amateur astronomers recognized the inherent advantages of an alt-az over an equatorial configuration.  Today, low cost, easily transported, and now mass produced “Dobsonian” telescopes. Now one can purchase quantity manufactured Dobsonian telescopes from 4 to 32 inches in aperture that cost from $100 to $34,000.  There are even a few larger and more expensive “Dobs” out there. 

Mel Bartels (1994, 1999, and 2000) developed a very low cost control for alt-az telescopes that employed a personal computer, a small electronics board, and three stepper motors for, respectively, altitude, azimuth, and instrument rotation. Soon Mel’s Compan, BB Astrosystems was selling the alt-az control system electronics for a very low cost.  The user supplied the stepper motors and a personal computer and computerized their Dobsonian telescopes.  More recently, Dan Gray’s Sidereal Technology has offered the electronics and software for a complete alt-az, DC servo control system, including instrument rotation and focus for about $1000. Dan graciously suggested he was inspired by Microcomputer Control of Telescopes (Trueblood and Genet 1985). 

For the second example of tech transfer from large to small alt-az telescopes, consider telescope weight, stiffness, and materials. As computers became more powerful, finite element analysis (FEA) resulted in increasingly lightweight yet stiffer large telescopes—leading eventually to today’s highly optimized truss structures. Lighter weights lowered costs, while stiffer structures allowed control systems to more effectively counter wind gusts.  Stiff and economical steel remained the material of choice for large alt-az telescopes. 

Dobsonian telescopes also evolved to become much lighter, stiffer, and more truss like.  They shifted from ordinary plywood and cardboard Sonatubes to hardwood veneer plywood and aluminum trusses. A recent small alt-az telescope, the 18-inch Cal Poly telescope (discussed further below), was designed by undergraduate engineering students using FEA, and features a carbon fiber composite structure. Carbon fiber composites have about three times the stiffness to weight ratio of steel. Although carbon fiber is too expensive a material to use in large telescopes, they can be an advantage in smaller telescopes.  

A good example of a modern, lightweight, alt-az telescope is Howard Banich’s (2004) 28-inch, computer-controlled, all aluminum alt-az telescope which weighs about 330 lbs. Howard transports his telescope in the back of a VW Eurovan, and can assemble or disassemble it in less than ten minutes. Watch Howard in action in a time-lapse video at
28inchteardownvideo. A somewhat similar telescope, SpicaEyes, is available commercially in apertures up to 32 inches.

(Left) Howard Banich’s portable 28 inch telescope at the first Alt-Az Initiative Workshop in Portland, June 2007.  Howard is on the left, and Russ Genet is on the right. (Right) One of SpicaEyes commercially produced all-aluminum, computer-controlled alt-az telescopes.

It might be noted in passing that not all tech transfers have been from large to small telescopes. Full telescope and observatory automation, remote Internet access, and global networking have all been pioneered by small telescopes. Larger telescopes subsequently adopted aspects of these technologies. These are all clear cases of reverse tech transfer. 

Two Separate Telescope Development Communities 

Although large to small alt-az telescope tech transfer is taking place, the fact is that the large and small developmental communities are, in the main, quite separate, with limited between-community communications. Large alt-az telescope developments are generally undertaken by a combination of paid professional engineers and astronomers.  These telescopes are built in high-bay machine shops equipped with large cranes. The cost of such telescopes now often exceeds $50 million, and the telescopes can weigh over 1 million pounds. Each telescope development is, typically, unique. Information is exchanged through the meetings and journals of engineering organizations such as the Society of Photo-optical Instrumentation Engineers (SPIE), and through professional astronomical meetings such as those organized by the American Astronomical Society (AAS).  A classic large telescope design book is The Design and Construction of Large Optical Telescopes (Beley 2003). 

The development of small, Dobsonian alt-az telescopes, on the other hand, has mainly been undertaken by unpaid amateur telescope makers (ATMs) as an avocation. It might be noted, however, that many ATMs are, by vocation, scientists, engineers, or technicians. These telescopes are being built at home or small manufacturing shops, often with simple tools. Costs are typically a few thousand dollars, and telescopes weigh a few hundred pounds. Although many ATM-built telescopes are unique, several small telescope manufacturers produce identical telescopes in quantity.  Information is not only exchanged on-line through a variety of email lists and web sites, but also through annual regional conferences such as the Riverside Telescope Makers Conference (RTMC). The quarterly journal, Amateur Telescope Making, which was the primary published record for Dobsonian developments for many years, has now been superseded by Amateur Astronomer. Sky & Telescope and Astronomy Technology Today also feature small telescope developmental articles. A classic small telescope book is The Dobsonian Telescope (Kriege and Berry 2003).


The past decade has seen great advances in the availability of research grade instrumentation suitable for smaller telescopes.  These advances have been driven by a combination of evolving technology and by the emergence of a community of advanced amateur astronomers with modest budgets but very high standards. 

This combination has allowed instrument makers such as SBIG, Optec, Shelyak, and others to bring to market products with capabilities that were previously available only to well financed institutions. Equally important has been the emergence of a software infrastructure (ASCOM) that unifies instrument automation and telescope control. 

To give just a few examples of progress over the last decade:  High quantum efficiency, science grade imaging cameras have gone from 1.5 mega pixels (MP) to 16 MP. Small telescope spectrographs, a category that hardly existed a decade ago, now include R~17K Littrow and fiber fed Echelle instruments. The cost of polarimetric instruments has declined by a factor of 10 thanks to achromatic polymer waveplates from Bolder Vision Optik.  And whole new instruments are now available such as the SSP-4 that provide JH band infrared photometry.  Small telescope IR spectrographs and imagers are within sight. 

These individual instruments are generally lightweight, well documented, essentially maintenance free, and have multivendor software support. Moreover, they were designed to match telescopes in the .3m to 1.5 meter range because that is where their customers are. 

Dedicated Telescopes, Automation, and Operation and Maintenance Costs 

General purpose telescopes, which have to meet a wide range of requirements, tend to be more expensive than dedicated telescopes to purchase, and certainly are more expensive to operate and maintain. The initial cost of a general purpose telescope at a major observatory, while it can be considerable, is typically much smaller than the long run operation and maintenance (O&M) costs over the telescope’s life time.  The cost of paying O&M staff for decades adds up. Furthermore, the cost of the instruments, substantial to begin with and expensive to upgrade over the years, can be a large fraction of the life cycle cost. The long-term burden of O&M costs at the national observatories became so high that a number of smaller scopes had to be closed because there was insufficient money both to operate them and also build and operate new, larger, cutting-edge research telescopes. 

Taking instruments on and off a telescope on a regular basis is costly in both manpower and equipment wear and tear. Dedicated telescope/instrument combinations, on the other hand, can be designed together for a specific mission area with the instruments permanently emplaced on the telescope. A computer-controlled selector moves the optical beam between the instruments in a cluster. Dedicated telescopes may be the way of the future, because they are cheaper to operate and maintain, particularly when they are operated in a service/robotic mode. 

If a dedicated telescope with a permanent, computer selectable cluster of instruments is run robotically, care has been taken to obtain high reliability components, and maintainability issues have been carefully addressed, then O&M costs can be quite low.  The National Science Foundation has traditionally funded the telescopes at colleges and universities, but not, of course, for individuals. However, if small, dedicated, robotic research telescopes could be made inexpensively enough, they might become affordable enough for individuals and small informal groups entirely on their own to purchase, operate, and maintain.

Undergraduate Student Research and Telescope Development

 The Initiative is actively pursuing the vital connection between small telescopes and the training of a new generation of astronomers and instrumentalists.  A number of institutions with limited budgets are developing research programs that utilize low cost telescope technology. To date, several dozen undergraduate students at Cuesta College have participated in astronomical research programs resulting in published papers.  They utilize both local observatories and remote, robotic observatories to observe a wide range of celestial phenomena including visual double stars, eclipsing binaries, intrinsic variable stars, asteroid rotation rates, and exoplanet transits. 

Cuesta College research seminar students observe an intrinsic variable star (left) and Arroyo Grande High School students (taking a Cuesta College research seminar) make astrometric measurements of visual double stars (right). Their results have been published in Society for Astronomical Science Symposium Proceedings, The Alt-Az Initiative (book in press), and the Journal of Double Star Observations.


Similarly, a dozen California Polytechnic State University, San Luis Obispo (Cal Poly) engineering (ME and EE) students have been or are currently involved in the design and fabrication of a research grade alt-az telescope, instrument rotator, and low cost, active primary mirror support electronics.

The Cal Poly engineering students present their design for an 18-inch Newtonian focus alt-az telescope at a critical design review (left). Two Cal Poly ME students fabricate the fork of the telescope. They designed the fork using finite element analysis (right). The foam core was later covered with multiple layers of carbon fiber cloth.

 These research and engineering students have given presentations at multiple Initiative workshops and conferences, and have coauthored Initiative papers. One Cuesta College student, Jo Johnson, co-chaired two Initiative conferences and is co-editing the Initiative’s forthcoming book.

Cuesta College student Jolyon Johnson co-chaired two conferences for the Alt-Az Initiative: the STAR Conference in California (left) and Galileo’s Legacy in Hawaii. Cal Poly engineering student Michelle Kirkup receives a certificate of recognition from Professor John Ridgely at the STAR Conference for her participation in designing the Cal Poly 18-inch alt-az telescope (right).


Lightweight Alt-Az Telescope Developments

Edited by
Russell Genet,  Jolyon Johnson,  &  Vera Wallen


Russell Genet, Jolyon Johnson, and Vera Wallen (left to right) are editing the Initiative’s book Lightweight Alt-Az Telescope Developments. This book discusses all aspects of the Initiative in detail (left). The cover of the Initiative book features the Initiative’s first production spin-off, PlaneWave Instruments CDK 700 telescope silhouetted against the galaxy M81 (right).


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