The Telescopes 
The 6-inch Refractor

Butler University's first telescope was a 6-inch refractor donated to the university in the late 1880s when the campus was located in Irvington on the east side of Indianapolis. The 6-inch recfractor can be seen in the image to the left.  It is the long telescope riding piggyback on the 38-inch tellescope. A refracting telescope uses a lens to gather light.  This light is then focused at the back of the telescope where the observer looks through the eyepiece.

When the Butler University moved to its current location in1927 the 6-inch telescope was used on top of Jordan Hall. Once Holcomb Observatory was built in 1954, this telescope was put onto the 38-inch Cassegrain telescope as a spotting/wide field telescope.  The telescope is still in good operating condition and now serves as our guide scope using a CCD camera.
 
The 38-inch Cassegrain

The main telescope in use at Holcomb Observatory is the 38-inch Cassegrain. This telescope along with the observatory was built in 1954. A Frenchman, Nicolas Cassegrain (1625-1712), invented this two mirror telescope.  Almost all modern telescopes follow this basic form to some degree. The diagram below illustrates the optical elements and the path that light takes through the telescope. The primary mirror has a parabolic shape and gathers light in the same way a refractor gathers light using  its objective lens. The secondary mirror, an hypebolic shape,  reflects the light back through a hole in the primary mirror.  The intruments and eyepiece are located near the focus behind the telescope.


Though the 38-inch Cassegrain is structurally and mechanically sound it was initially difficult for the observer to use. In order to go from object to object the observer had to physically move the large telescope by hand. In addition after many years of  addition and subtraction of equipment the telescope was grossly out of balance and years of wear and tear made the telescope's tracking suspect. With the advent of students using CCDs for data acquisition it became apparent that the telescope should be automated and incorporate precession tracking and positioning via a computer. This automation would allow students to more easily acquire targets and data making observing sessions a more pleasant learning/research experience.

In 1994 Butler University began the first phases to upgrade the 38-inch telescope.  Upgrading the large telescope proved a significant challenge for the university.   The university hired AB Engineering of Ft. Wayne, Indiana for the upgrade. They proposed a retrofit of  the mount with computer controlled  polar and declination axis drives. This project required the replacement of the original polar axis worm with a new precision worm assembly and the declination tangent arm with a 26-inch diameter worm gear set. Each axis is driven by a single stepper motor providing both tracking and slewing operation.   The  encoders and stepper motors are controlled by a Telescope Control Computer in the telescope dome. A dedicated, solid state controller orchestrates motion control and position monitoring. The telescope's position is displayed via digital setting circles on a large character LED display, mounted on the wall of the observatory and on Software Bisques' The SkyTM via a virtual RS-232 connection or the local area network. An integrated GPS receiver provides time and location initialization. Operator control of the telescope is through a hand-held paddle or through a PC via the Internet. A motion warning system notifies personnel within the observatory when the telescope is slewing and when slew limits are being approached. 

The upgrade highlights included:

The first phase of refurbished telescope was finished in April 1997 and commenced operation, with Mr. Tom Bopp, co-discoverer of comet Hale-Bopp, presiding. In 2001 the final automazation was completed.  The telescope is now fully automated so that it can be run robotically and remotely and carry out an single nights's observing program unattend.