1. Teleskop Modern AS3200 Lab. Astronomi Dasar II Prodi Astronomi 2007/2008 B. Dermawan

2. To Dreamers, Then, Now, and Always Majewski

3. Trends in Modern Telescope Development Light gathering power Kualitas & sensitivitas instrumen  efisiensi Resolusi (kualitas citra & sensitivitas)  efisiensi Majewski Bely

4. Trends in Modern Telescope Development Sensitivitas Instrumen - Perbaikan pada desain optik, optik, detektor - Temuan baru (fiber optics, holographic gratings) - Menemukan tempat observasi baru Resolusi - Guiding cepat & otomatis - Pemahaman yg lebih baik tentang efek seeing - Penentuan tempat observasi dgn seeing yg baik - Perbaikan pada cermin & desain dome - Active mirror figure & atmospheric compensation - Pengamatan space-based - Interferometry Majewski Bely

5. Large Mirrors: Shapes, Materials & Types Telescope f-ratio Majewski Fast primaries: biaya operasional, tabung kecil  kukuh, kecil wind cross- section, secondary mirror lebih kecil Bely Difficult decisions: tipe & konstruksi cermin utama, konfigurasi optik, struktur/ukuran/kontrol tel., desain instrumen optik, ukuran dome, tempat yg potensial utk teleskop, biaya total

6. Large Mirrors: Shapes, Materials & Types Lightweighting mirror Majewski HST LBT, abell.as.arizona.edu/~hill/mirror Bely

7. Large Mirrors: Shapes, Materials & Types Segmented mirrors Majewski Size limited of monolithic mirrors: fasilitas pabrikan, sukar mendapatkan hasil homogen, sukar pada handling & transport, max. 4-m untuk space telescope Advantages of segmented mirrors: massa rendah, singkat konstanta waktu termal, segmen dapat diganti, ukuran aperture tidak terbatas

8. Large Mirrors: Shapes, Materials & Types Segmented mirrors Majewski However: all segments must be figured to be parts of one parent shape (“off- axis" paraboloidal segments tricky and expensive), all segments must be kept precisely and actively aligned despite changing gravity, thermal effects, wind, etc. Segmentation geometry: “petals" / "keystone" -- radial/azimuthal segments, hexagons (put down in rings) Bely

9. Large Mirrors: Shapes, Materials & Types Segmented mirrors Majewski 1.8-m Guido Horn-d'Arturo 6-mirror (~4.5-m) to a single mirror 6.5-m MMT www.mmto.org/pr_images/upgrade.html

10. Large Mirrors: Shapes, Materials & Types Segmented mirrors Majewski Hobby-Eberly Telescope (HET) South Africa Large Telescope (SALT)

11. Large Mirrors: Shapes, Materials & Types Segmented mirrors Majewski Keck I & II

12. Large Mirrors: Shapes, Materials & Types Segmented mirrors Majewski Large Binocular Telescope (LBT)

13. Large Mirrors: Shapes, Materials & Types Tubes, Trusses, & Baffling Majewski Heavy, under gravity  de-collimate the optics, presents a large wind cross-section, prevents air from flowing across & cooling mirror Serruir Truss: open structure based on isosceles triangles on a square base When vertical triangles deflect, the parallelogram of horizontal triangles constrains the tube ends to move in a parallel plane  mass inefficiency & use of active optics Multi-bay structure HST Keck Gemini Bely

14. Large Mirrors: Shapes, Materials & Types Tubes, Trusses, & Baffling Majewski Preventing scattered light  baffling Generally conical or cylindrical tubes enclosing parts of the beam Often include perpendicular vanes to force radiation to make multiple scatters Bely Demands for wide field imaging are more severe

15. Large Mirrors: Shapes, Materials & Types Tubes, Trusses, & Baffling Majewski Reflections off of the primary or secondary: scattering of off-axis rays off of dust Critically important for space telescope HST: numerous vanes and both secondary and primary conical baffles (all black) Bely

16. Large Mirrors: Shapes, Materials & Types Mounts Majewski Before 1980 nearly all telescopes were mounted with an equatorial mount: counteract Earth rotation by motion only on one, polar axis, simple correction with single speed, no field rotation in focal plane Now most telescopes are built with altitude-azimuth (alt- az) mounts: neither axis changes direction with respect to gravity, structurally sturdier than equatorial, less massive, less expensive BUT: three axes of rotation needed: altitude (h), azimuth (A), and field rotation, all three axes move with variable speed, could only do this with fast computers Bely

17. Teleskop Subaru (1) www.subarutelescope.org

18. Teleskop Subaru (2) www.subarutelescope.org

19. Large Mirrors: Shapes, Materials & Types The biggest existing telescopes Majewski IFA, Univ of Hawaii

20. Large Mirrors: Shapes, Materials & Types The biggest existing telescopes Majewski Bely

21. Large Mirrors: Shapes, Materials & Types Some Proposed/Planned Large, Ground-based Telescopes Majewski Large Synoptic Survey Telescope (LSST) Proposed 8.4-m telescope with enormous 10 square degree field 3 billion pixel camera Will cover the entire sky with 10 second integrations every three nights Find fast moving or variable objects Build up a deep survey image of the sky in multiple wavelengths

22. Large Mirrors: Shapes, Materials & Types Some Proposed/Planned Large, Ground-based Telescopes Majewski Giant Magellan Telescope Seven 8.4-m Arizona Mirror Lab borosilicate honeycomb mirrors Light gathering power equivalent to a 21.4-m filled aperture Diffraction limited resolution equivalent to a 24.5-m filled aperture f/8.4 Gregorian with adaptive optics secondary Chile Partners: Carnegie Observatories, Harvard, MIT, SAO, Texas A&M, Arizona, Michigan, Texas

23. Large Mirrors: Shapes, Materials & Types Some Proposed/Planned Large, Ground-based Telescopes Majewski Thirty Meter Telescope (TMT) project A joining of several separate efforts: California Extremely Large Telescope (CELT) -- Caltech/UC Giant Segmented Mirror Telescope (GSMT) -- AURA Very Large Optical Telescope (VLOT) -- Canada

24. Large Mirrors: Shapes, Materials & Types Scientific productivity of telescopes Majewski Bely Suggests that scientific productivity scales by collecting area But cost is roughly proportional to diameter 2 or diameter 3, so the cost- effectiveness of a ground-based telescope is roughly independent of size, or maybe even somewhat favoring smaller apertures Of course, there is some science that simply demands the largest telescopes

25. New Technology “Surfaces” Liquid mirror telescopes (LMTs) Majewski Newton originally proposed using a rotating liquid (e.g., mercury) itself as a perfect paraboloid, but first done for 35 cm telescope in 1872 Revived in last few decades (primarily by Canadian collaborations) as technical problems overcome Primary limitation is that they can only look at zenith: limits science to survey type projects, with drift-scan CCD imaging http://www.phys.psu.edu/~cowen/popular- articles/sciam/1299musserbox6.html

26. New Technology “Surfaces” Primary technical challenge is suppression of ripples on surface from: wind, vibrations, misalignment of rotational axis Air bearings are one modern solution to smooth, accurate rotation Primary practical problem is that mercury vapors and oxides are very toxic But a big advantage is cost: The Large Zenith Telescope, a 6-m LMT, is being built at a cost of about $500,000 (which is 1% the cost of a conventional telescope of similar aperture) Majewski http://www.phys.psu.edu/~cowen/popular- articles/sciam/1299musserbox6.html