IES completes refurbishment of the Birr Telescope

Optical techniques are a a passion of mine: but this is a good story about the amazing Birr telescope in Ireland, where IES helped by completing the control system refurbishment

This historical scientific landmark is located in County Offaly, in the heart of Ireland.

The Birr Telescope reigned for more than seventy years as the largest telescope in the world.

Also known as "The Leviathan of Parsonstown," the giant reflecting telescope was the 19th century vision and creation of William Parsons, the 3rd Lord of Rosse.

On February 15, 1845, three years after construction began, the Birr Telescope provided the most magnified view of the sky possible at the time.

Until the completion in 1917 of the 100 inch Hooker telescope at Mount Wilson in California, the Birr Telescope beckoned to astronomers of the day as the tool to aid their study and exploration of the heavens.

The 72 inch mirror, mounted in a 56 foot long tube, weighed 3 tons.

The lower end of the telescope was set on a cast iron universal joint, which sat on a masonry base.

Chains controlled by a hand winch, raised and lowered the far end of the telescope.

Support for the chains, as well as protection from the wind, was provided by two massive stone walls, one on each side, 50 feet high and 70 feet long.

Using the telescope was a not for the faint of heart, since the observer had be as much as 60 feet in the air on a scaffold like device, which accommodated the movement of the telescope as it tracked an object in the sky.

Technology of the day made it impractical for Lord Rosse to have the parts for his telescope manufactured outside of Ireland, and facilities didn't exist nearby.

He not only designed the telescope, but manufactured it.

He made the machinery necessary to manufacture the parts.

This was truly a telescope of Ireland.

The mirror is the most outstanding feature of the Birr Telescope, and the greatest testament to Lord Rosse's skill as a designer.

The technology didn't exist to cast a metal coated glass mirror of that size.

Speculum metal, an alloy of copper and tin, was used.

The casting was accomplished with three crucibles, each 24 inches in diameter and weighing 1/2 ton.

Surrounding bogland supplied the turf which produced the heat needed to melt the metal.

The process was a difficult one: the higher the tin content, the more reflective the mirror, yet a higher tin content could cause the mirror to become brittle and break.

Lord Rosse built a foundry in the bottom of the Birr Castle moat to cast the mirror.

Two mirrors were made so that one would always be available while the other was being polished.

The Birr telescope mirror remains the largest metal mirror in the world today.

The innovative design which allowed for the construction of a large telescope caused the Birr telescope to have a restricted range.

The wall that protected it, also prevented it from swinging around in a circular motion.

Its range was limited to a north/south direction along the meridian meaning an hour was the longest time in which the motion of a star or nebula could be tracked.

Many prominent telescope makers of the day ridiculed the Birr Telescope and Lord Rosse.

Astronomers, on the other hand, flocked to Birr Castle from all over the world for a chance to see the skies in more detail than anyone else of that time.

Lord Rosse would go on to identify many celestial objects.

It was Lord Rosse, using the Birr Telescope who first described the spiral nature of nebulae and recognized them as galaxies outside our own, containing stars and thus disproving the prevailing theory that they were merely objects made of dust within our own galaxy.

After Lord Rosse died, his son continued to maintain and use the telescope.

However, after his death, the Birr Telescope fell into disuse and disrepair.

Parts of it were dismantled.

The mirror was taken to the Science Museum in London, where it still resides.

Attempts to restore the telescope during the 1960s fell short.

In 1994 with the help of private, business, and governmental funding and determination, restoration of the Birr Telescope was begun and finally completed in 1999, with the hope that it would occasionally be used for its original purpose, bringing the heavens into closer view.

Unfortunately after the recommissioning it was found that the control system being used was inadequate and unable to provide the precision required for positioning the Telescope.

Fast forward to 2006 and enter IES.

IES were awarded the brief to design, install and commission a replacement with the key objectives to:.

* Provide a system capable of automatic operation for demonstration purposes to visitors and manual operation for use by Astronomy observers.

* Replace the existing Control System with a modern well supported one.

* Relocate the Operator Station PC from its external environment to inside the building.

* Provide the necessary safety precautions and interlocks in the control system to ensure safe operation.

The system also provides the Alarms and Interlocks to prevent inappropriate operation.

This is provided by : 50 Proximity switches, 3 external E-stop buttons and 4 anti collision sensors.

In addition to the controller, the scope of the ies contract for the upgrade encompassed:.

Software design, coding and testing for functionality.

Replacement of DC drives and clutches.

Replacement of proximity / limit switches.

Replacement of E-stop buttons.

Replacement of Anti-collision sensors.

Recalibration of Inclinometer.

Recalibration of Pull wire sensor.

The system has 4 password protected levels of access, namely: View Only, Operator, Maintenance, Administrator.

The system was redesigned to provide three modes of operation: Manual, Demonstration, Observer.

In the Observer Mode the telescope can be positioned by pressing the appropriate button (up/down/east/west) until the desired viewing position is achieved.

Alternatively the observer has the facility to enter in a desired angle of elevation and azimuth angle.

These set points are entered via the touch screen..

Once the set points are entered the user presses the "Start" pushbutton on the console, which positions the telescope appropriately.

Starting from zero the motors ramp up to their max speed and then ramp down when the button is released, providing a smooth stop.

Once the position has been reached the motor positioning control is deactivated to allow the operator to carry out small adjustments using the handles.

For more information on the fascinating Birr telescope which is now operational with our help, please follow the link.

Please do give Birr Castle a visit if you are in Ireland, it's a great family day out.

Birr Castle, Demesne: http://www.birrcastle.com/index.asp.

See other IES PCS news for water industry and other control schemes on Processingtalk: http://www.processingtalk.com/news/ies/ies000.html.

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