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24-Inch B&C Telescope

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24-Inch Telescope
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Background

24-Inch Telescope The 24-inch Boller & Chivens f/8 Cassegrain was installed in the dome of Sommers-Bausch Observatory in 1973. Originally equipped for visual viewing, 4x5 film photography, photomultiplier photometry, and glass-plate stellar spectroscopy, the 24-inch now utilizes CCD electronic technology to achieve the same results: astroimaging, spectroscopy, and photometry. If you're interested in details, here are the telescope specifications.

For the first eight years of its life, the 24-inch was the sole telescope at SBO, and was kept busy seven nights a week with undergraduate observing sessions, graduate research, and public open houses. Now, it is used primarily by APS graduate students as a training and data-gathering instrument in preparation for observing runs at larger telescope facilities. Beginning in spring 2000, when the departmental major in astronomy is initiated, the 24-inch is expected to see considerable use once more by undergraduates, especially by upper-division astronomy majors.

The original instrument to occupy the dome was the 10.5-inch Bausch telescope, which was installed in the new Observatory building in 1953. The 25-foot diameter dome was necessary to encompass the long, f/15.5 refractor. Now, with the much shorter 24-inch with folded optics, the dome offers plenty of elbow room, even after the installation of a false floor and separate instrument room (referred to as the Coude Room, even though the Coude focus has never been used). The mirrors one sees around the periphery of the dome are historical left-overs from the transition between the long-and-narrow refractor and its replacement short-and-fat reflector.

In order to fully appreciate the fine detail and workmanship that went into the Boller & Chivens telescope, one needs to take it apart - which we do, on occasion, to do some mirror cleaning.

The 24-inch has seen some well-known visitors in its time - including the captain of the starship Enterprise and the only human being to play a round of golf on the Moon.


24-Inch Operations Manuals

of the 24-inch telescope and related equipment, available in Adobe Acrobat PDF format


CCD Detectors


TI CCD Charge-coupled device (CCD) detectors are almost exclusively used on the 24-inch telescope - either for imaging, spectroscopy, or photometry. With a 60-fold improvement in sensitivity over photographic emulsions, the use of a CCD gives the 24-inch the light-detection capability equivalent to that achieved by the 200-inch telescope at Mount Palomar back in the 1970's (before CCDs were invented and everyone had to use photographic plates).

At SBO, we use one of two CCD detectors with the 24-inch. The original, the Texas Instrument 800x800 CCD, has been in operation for over twelve years. While this detector is the most sensitive of the two, it is expensive to maintain and more complex to operate. As a result, we've added a second detector, the SBIG ST-8 CCD to our arsenal, which provides us with a larger format image in a PC-friendly data acquisition environment, at the expense of lower sensitivity and poorer detectability.


Imaging


Crab Nebula Before the advent of the CCD detector, most of the astrophotography on the 24-inch used the 4x5-inch film camera - producing large-format images such as the one shown here. Nowadays, 24-inch telescope users aren't usually after "pretty pictures" when using the CCD detectors; rather, they're using the camera as a highly-accurate and sensitive linear detector, which enables them to do photometry - accurate brightness measurements - of specific objects of research interest. Often, these objects are quite faint as well, which means that the don't lend themselves to attractive photographs. As a result, we don't have a large collection of "show-and-tell" astroimages that were taken through the 24-inch.

Nevertheless, there are a few nice ones that have come our way. One of our favorite sets is the work done by Karen Bjorkman early-on with the TI CCD - a collection of false-color images.

We also refer you to some of the images that appear on SBO's Gallery Page:


Spectroscopy


Grating Many people are surprised to learn that astronomers spend little time anymore staring into an eyepiece - or even clicking the shutter on a camera. Instead, the largest portion of astronomical information comes from spectroscopy - using gratings, such as the one shown here to break starlight into its component spectrum of colors - which permits the researcher to discover facets about the universe that would otherwise remain completely unknown. Using this technique, astronomers can determine the composition of stars, their speed of rotation, temperature, the strength of their magnetic fields, surface pressure and density, among other things; plus gas flows, the presence of unseen planets; and even measure the expansion of the universe itself.

The spectrograph used on the 24-inch - although unable to gather data on the faint objects that are at the leading edge of astronomical research - is still a useful and effective training tool for graduate students who will eventually have access to the "big toys" at major research instruments. And if the object is bright enough, we can still gather some useful data, such as:


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