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Student Observatory

Student Observatory
Linda A. Cicero, Stanford Magazine

The Stanford Astronomy Program, through the department of Physics, administers a small teaching observatory for the education and research of its students and faculty. The Student Observatory [map] is located in the hills above the Stanford golf course. While not open to the public on a regular basis, the facility is visible from Junipero Serra and I-280 as the brown cantilevered building with a silver dome to the north of the Dish, the Stanford/SRI 45' radio telescope.

Observational courses are taught during the Spring, Summer and Fall. Physics 50 is primarily for non-science undergraduates interested in the basic techniques of small telescope observations, presented at a non-technical level. In Physics 100, students with a more technical background (e.g. a full year of college physics) can pursue more sophisticated projects, with an increased emphasis on quantitative measurement and spectroscopy. Physics 301 allows graduate students to gain experience with some basic observational techniques; the course is often project based, focused on construction and testing of a piece of observing equipment. In addition, seminars, such as Phy 81, are taught using the observational facilities and students may pursue honors research at the observatory. A number of courses also schedule viewing nights at the facility, associated with class work treating astrophysics.

The observatory is not set up for public viewing. Foothill college in Los Altos Hills, just south of Stanford has a regular schedule of public viewing.

Stanford students interested in astronomy and telescopes may also contact the Stanford Astronomical Society.

Origin and History  Eye on the Sky - Stanford Magazine May 2011

 

In the early 1970's, a group of physics/engineering freshmen with a strong interest in astronomy were having a dormitory dinner with their advisor Professor Walter Meyerhof, chair of physics at the time, and were discussing the limited astronomy offerings on campus. According to Nick Suntzeff, "Somehow the topic of an observatory came up. We naively sketched out what it would take to build a small observatory. Dr. Meyerhof told us something like 'Well, why don't you try to build it!'"  The resulting project occupied a substantial fraction of the next four years for student leaders Michael Kast and Nick Suntzeff. Many students and faculty contributed: architecture student Kenneth Kornberg did the basic design and Greg Howell led much of the major construction. Physics students Sally Ride and Doane Farmer also spent appreciable time on the project. Some of the undergraduates received academic credit for the project from the SPIRE program.

Walter Meyerhof remained faculty advisor for the effort. Financial assistance was contributed by the President's office, the Departments of Physics and Mechanical Engineering, Bechtel Corporation and the NSF. However, the real hallmark of the project was the students' efforts to acquire donated or scrap equipment and materials when the resources were limited. For example the dome was a discard from Leuschner Observatory, apparently built in 1905! The Boller&Chivens mount (one of the earliest B&C mounts) came from North American Rockwell and was originally used for missile tracking. The pier tube was a scrap wind tunnel from an engineering junk-heap.

Construction was an education and an adventure. According to Suntzeff, 'innovative' solutions had to be found for many financial and engineering challenges. "The dome was way too big to take on the freeway, but we crossed our fingers and the CHP never caught us.'' Also, "I remember one of the junior faculty with a pencil and paper trying to figure out a dual 3-way light switch from first principles.'' Greg Howell was particularly adept at making do: "To erect the pier which was about 25 feet tall, he only had a crane which was about 25 feet tall. He jacked up the front end of the crane, started lifting the pier upright, and somewhere near vertical, he jerked the crane up while jumping out of the crane and ran for safety. The pier magically righted itself. He told me that he had done this before.''

This effort resulted in the present observatory, which contains a main building with lab space, a teaching room with a small library, a washroom and two small darkrooms. Outside stairs lead to a separate observatory floor, ~35 feet above ground level, with an observing room covered by a 15' dome and a storage/work annex.

The original telescope was a commercial 16" Cassegrain, but this suffered from poor optics, and was replaced with an early model C-14 Celestron Schmidt-Cassegrain. A small 8" S-C and an 8" Schmidt camera were co-mounted for a number of years.

Many of the student principals went on to careers in engineering, space science and astronomy. Activity in astrophysics at Stanford has grown immensely since the 70s and is now a major facet of work in the Physics department. The Observatory continues to get heavy use and many hundreds of students have received initial exposure to astronomy and basic training in observational techniques there.

We are grateful to Nick Suntzeff, currently at the Cerro Tololo InterAmerican Observatory, for reminiscences about the early days and would enjoy hearing from others involved in the project.

RETROFIT AND UPGRADE OF OBSERVATORY FACILITIES, LATE 1990'S

It had been clear for some time that full use of the Observatory for teaching and student research would require significant upgrade of the existing facilities. In particular, the worm gears on the Boller and Chivens mount had experienced a lot of wear and large amounts of backlash made it difficult to guide to better than about 10". In addition the relatively poor setting performance and the lack of computer control significantly hampered the ability to have students acquire objects and complete experiments efficiently. With the advent of modest cost autoguiders and CCD cameras, computer drive control would also significantly enhance opportunities for student research projects. Thus a rebuild of the mount has been a cornerstone of this upgrade project. Further more substantial aperture and improved optics are being acquired to expand the range of research projects and to take advantage of the moderate site seeing, which can be better than 1.5".

The telescope upgrade project has been organized by Roger Romani (Physics), with financial resources from the Astronomy program Bunyan funds, the school of H&S Freshman seminar incentive funds, Summer Session support funds and the Department of Physics. Rosenna Yau and Rick Pam have also been especially helpful in assisting with this project.

Some major component of current and future facility upgrade are listed below:

Mount: Pointing and Drive Control

The massive (1200lb) B&C extended polar axis German equatorial mount has been rebuilt by AB Engineering of Ft Wayne, Indiana. This rebuild features: 24" and 18" RA and DEC worm gears, complete anti-backlash mechanisms, drive encoders, computer synthesis of drive correction, paddle and autoguider control, pointing under control of an external computer running The Sky(TM), a GPS reference for absolute position and external large LED displays of coordinates for student reference. The mount was removed from the dome via crane on Dec 7th, 1997 (JPEGs from the crane lift can be downloaded from the thumbnails below.)

 

The updated mount has now been used for several years with very good results. With correct balance and PE training, the residual tracking error is under 1" open loop for many parts of the sky. Setting under tpoint requires occasional updating, but is generally within 1 arcmin for most positions. The autoguiding (generally with an ST6 camera) works well and the mount control also connects to a computer-controlled dome rotation system. This control, also provided by AB engineering, allows dome tracking of the mount position during long guided exposures.

Special thanks go to Neill Germann for donating his time and effort in 2015-2016 to update his original software after nearly 20 years!

Optical Tube Assembly

 

A 24" Cassegrain/Newtonian has been built for the project by `Torus Precision Optics' of Iowa City, Iowa. This is a custom design with an f/3.5 0.61m primary mirror, an f/10 classical Cassegrain focus and a fast f/3.5 Newtonian port. The tube assembly is an open truss, and the Cass and Newtonian secondaries are position back-to-back on a spider in the headring. Changeover between the two foci is accomplished by `flipping' the headring and spider. There is computer driven, encoded focusing at each port. A commercial coma corrector/field flattener is used increase the usable Newtonian field to nearly one degree at f/4.

The OTA has required some baffling at the secondary to reduce direct skylight for wide FOV instruments. Recently we have also added a fabric light shroud to combat light scattered from the dome off the (presently) rather dusty optics. The optical performance is generally adequate, although significant astigmatism in the system and print-through from the secondary mirror holder are issues under the best seeing conditions. The upper truss is also somewhat prone to sag, requiring frequent re-focus as the telescope is repointed.

Separate ADA Facility

To increase student use of the observatory we have installed a smaller fiberglass dome on a concrete pad to the SW of the main observatory. The floor slab is at ground level, making this facility more accessible for students with disabilities. This dome requires hand rotation -- a shutter clamping mechanism has been developed (courtesy P. Boerner) which is needed to survive occasional winter high winds. This dome originally housed the venerable C-14, but a generous donation of an underused 16"LX200 by alum David Siminoff has allowed us to replace this with a more modern telesocpe. The 'scope has been equatorially mounted, focal-reduced to f/6.3 and equipped for wide-field CCD imaging. complementing the main telescope. This telescope is also currently the only permanent installation allowing eyepiece viewing.

Detectors and Computers

The control and analysis computers at the observatory are connected in a LAN, which facilitates student observations and data reduction. Unfortunately this LAN does not have a permanent internet link.

At Cass focus, the O.6m uses a Van Slyke flip mirror to select between direct imaging (1024x1024-24mu SITe camera -- Apogee AP8, together with a Finger Lakes filterwheel housing 50mm BGRI filters) and spectroscopic set ups. We have a new long-slit grating spectrograph (designed by K. Thompson, funded by the the Physics Department and Astronomy Program, and constructed with assistance from Phy301 students, especially T.J. Bay, J. Burney and C.-Y. Ng) which is being (slowly) comissioned in its several resolution modes. The user may choose btween low resolution (prism, at present) dispersion and 600 and 2400l/mm gratings. We have slit viewing for acquisition and set-up. The spectrograph camera is an Apogee AP-7, which provides modest dark current and ~200nm optical coverage with the medium resolution 600l/mm grating. We also have transmission gratngs for insertion in the f/10 beam which provide slitless spectroscopy with the imaging system. Off axis autoguiding need not be interupted when switching between imaging and spectroscopy.
The 0.4m (16"LX200) has a Meade Pictor 161 at f/6.3, computer- controlled filter selection and ST-4 autoguiding. Pending tracking improvement of the mount, imaging is generally restricted to modest (few minute exposures) w/o guiding. There is also an eyepiece port.

Since the upgrade, numerous experiments have also been conducted with a variety of new technologies, including superconducting detectors and wavefront sensors.