Telescope Design

1. Telescope Design ME 250 Precision Machine Design Prof - Dr. B. J . Furman By: Kamalakar Pegadarju & Sandeep Kadam ME 250 Presentation - Telescope Design

2. Introduction • What is a telescope? • A telescope is an amazing device that has the ability to make faraway objects appear much closer. • Telescopes come in all shapes and sizes • Features of telescope • Magnification • Light Gathering • Aperture and resolving power ME 250 Presentation - Telescope Design

3. Introduction • How telescopes work: • The objective lens (in refractors) or primary mirror (in reflectors) collects lots of light from a distant object and brings that light, or image, to a point or focus. • An eyepiece lens takes the bright light from the focus of the objective lens or primary mirror and "spreads it out" (magnifies it) to take up a large portion of the retina. • When you combine the objective lens or primary mirror with the eyepiece, you have a telescope. ME 250 Presentation - Telescope Design Fig 1.1Telescope Design (Source: howstuffworks)

4. Introduction • Types of Telescope: • Refractors Long, thin telescopes that use a lens at the front of the telescope tube to collect light. • Newtonian Reflectors Newtonian Reflectors use a highly polished, curved mirror at the rear of the telescope tube to collect light. • Catadioptric Compound optical systems i.e both mirrors and lenses are employed to collect and focus incoming light. Fig 1.2 Refractors Fig 1.3 Reflectors Fig 1.4 Catadioptric ME 250 Presentation - Telescope Design (Source: http://www.e-sci.com)

5. Telescope Mount The telescope mount allows to: • keep the telescope steady • point the telescope at the stars or other object (birds) • adjust the telescope for the movement of the stars caused by the Earth's rotation • free your hands for other activities (focusing, changing eyepieces, note-taking, drawing) There are two basic types of telescope mounts: • Alt-azimuth • The alt-azimuth mount has two axes of rotation, a horizontal axis and a vertical axis • Equatorial • The equatorial mount also has two perpendicular axes of rotation -- right ascension and declination. ME 250 Presentation - Telescope Design

6. Telescope Mounts Fig 1.5 Diagram of telescope types and mounts. ME 250 Presentation - Telescope Design (Source: howstuffworks)

7. Telescope Components • Base The base of the telescope acts as a firm support for the structure of the instrument. • Azimuth Ring Azimuth ring makes the telescope move round on the azimuth axis. • Hydrostatic bearings Cope with the weight of the telescope and smooth smooth, low friction, low stiction, and near zero hysteresis motion. • Yoke The yokes provide the second axis of movement for the telescope as well as supporting the mirrors, instruments and associated mounting structures. • Trusses Trusses are positioned to form triangles along which the stresses can travel to avoid the bending caused by weight of the mirrors Fig 1.6 Hydrostatic bearing Azimuth Ring Base Fig 1.7 Azimuth ring ME 250 Presentation - Telescope Design (source: http://www.schoolsobservatory.org.uk )

8. Telescope Components Trusses Yoke Mirror Cell Base Fig 1.8 Components of Telescope ME 250 Presentation - Telescope Design (source: http://www.schoolsobservatory.org.uk )

9. Ninety one hexagonal mirrors 1 meter across the flats to form a hexagonal parent mirror. Hindle mounts providing 9 support points Hindle type system are supported by electromechanical actuators consisting of commercial motor micrometers acting through reduction lever flexures Resolution of 0.24 micro radians in tilt and 0.1microns in position to achieve adequate performance for spectroscopy. Primary Mirror in Spectoscopic Survey Telecsope ME 250 Presentation - Telescope Design 566/SPIE Vol.2199

10. Hindle Mount in SST • Fig 1.8 Perimeter Shape of the segments and location of the hindle mounts ME 250 Presentation - Telescope Design

11. Primary Mirror Truss in Spectoscopic Survey Telecsope • Primary mirror segment assemblies are supported on a space frame truss . • 11 meters across and is formed of 1,758 struts and 389 nodes • Provides comparable overall stiffness and superior node positioning accuracies of 1.5 mm. • The truss mounts to the overall telescope tube and base structural assembly via a kinematic mount. ME 250 Presentation - Telescope Design 568/SPIE Vol 2199

12. Primary Mirror Truss in Spectoscopic Survey Telecsope • Fig 1.9 Formation of truss ME 250 Presentation - Telescope Design 568/SPIE Vol 2199

13. Kinematic mount for primary mirror Fig 1.10 Kinematic mount for primary mirror ME 250 Presentation - Telescope Design 568/SPIE Vol 2199

14. Primary Mirror Truss • Distortion of the telescope tube and base frame resulting from the azimuth rotation between observations does not distort the primary mirror assembly. • “three ball-three groove” mount • The kinematic mount is intended to isolate the primary mirror truss from distortions of the base frame caused by rotation to varying azimuth positions. • maximum forces at each mount which the truss can tolerate within established error budgets is 25 lbs lateral force and 5 ft-lb moment. ME 250 Presentation - Telescope Design

15. Large Binocular Telescope • Reference plate • Cold plate • Support frame and electronic boxes ME 250 Presentation - Telescope Design See Reference#7

16. Large Binocular Telescope Fig 1.11 Detail of the cold plate and back plate with electromagnetic actuators. The flexure that connects the reference plate and the aluminum one represented in a false orientation to show its components ME 250 Presentation - Telescope Design See Reference#7

17. References 1.) Thornton Page & Lou Williams Page., Telescopes: How to make them and use them, The Macmillan Company, New York. 2.) Craig C. Freudenrich, Ph.D., How Telescope work, Howstuffworks, Inc. (www.howstuffworks.com) 3.) Types of Telescope Designs, Efston Science, The Science and Economy superstore. ( http:www.e-sci.com) 4.) Richard Berry., Build your own telescope, Collier Macmillan Canada, Inc 5.) http://www.schoolsobservatory.org.uk     6.) Thomas A. Sebring, John A,.Booth , John M. Good, Victor L. Krabbendam, Frank B.Ray., Design and status of the Spectroscopic Survey Telescope, University of Texas, SPIE Vol. 2199, 1994. 7.)D. Gallieni , C. Del Vecchio , E. Anaclerio , P. G. Lazzarini, LBT adaptive secondary preliminary design., ADS International S.r.l., c.so Promessi Sposi 23/d, 23900 Lecco, Italy, 1993 ME 250 Presentation - Telescope Design

18. Questions???????? ME 250 Presentation - Telescope Design