Development of the Modern Large Telescope

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Development of the Modern Large Telescope

• by Josh Walawender

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The Equatorial Giants

• 1917 (Mt. Wilson) ? 1974 (CTIO 4m)
• monolithic mirrors
• large equatorial mountings
• photographic plates as detector
• very similar designs (few innovations)

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1917 -- First equatorial giant ? 100 inch (2.5m)
Hooker telescope on Mt. Wilson
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1948 200 inch (5 meter) on Mt. Palomar
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1973 Mayall 4 meter (158 inch) at Kitt
Peak 1974 Blanco 4 meter (158 inch) at Cerro
Tololo ? first large public telescopes
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Using The Equatorial Giants

• Using a large telescope requires real
  mastery of a beautiful and cantankerous
  instrument.
• A. E. Whitford
• Manual guiding
• eventually replaced by autoguider
• Made for photographic plates

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Modernizing the Telescope

• move to alt-az mountings
• requires computers
• move to non-classical domes
• try new innovative optical designs
• still in the 4 meter size class
• spincasting
• multiple mirrors (MMT)
• ARC, WIYN, SOAR
• collaborations now own telescopes
• APO/ARC JHU, NMSU, Princeton, Chicago, CU, UW
• WIYN Wisconsin, Indiana, Yale, NOAO
• SOAR Brazil, NOAO, UNC, Michigan State

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1979 The MMT (six 1.8m mirrors)

• used a complex beam combining system ? small
  field of view
• alt-az mounting, non-traditional dome
• now has been replaced with a single 6.5 meter
  mirror

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1991 Apache Point Observatory (3.5 meter)
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1994 WIYN (Wisconsin Indiana Yale NOAO) 3.5
meter
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2004 SOAR (Southern Observatory for
Astrophysical Research) 4 meter
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Gemini South and SOAR are on Cerro Pachon next
door to CTIO
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Using a Modernized Telescope

• The observer is moved into a heated, computerized
  control room
• sometimes in a completely different building
• Observing specialists control the telescope
• The observer controls the instrument and monitors
  the data
• Some can be used remotely

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ARC Remote Operation
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The Modern Giants

• 8-10 meter mirrors using new technologies
• spincast, honeycomb mirror
• meniscus mirrors (active optics)
• segmented mirrors

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The Modern Giants
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The 10m Keck Telescopes
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The 8.3m Subaru Telescope
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The 8.2m VLT Telescopes
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The Very Large Telescope
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The 8.1m Gemini Telescopes
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Using The Modern Giants

• The observer is moved as far from the telescope
  as possible!
• Queue Observing
• observer submits an observing plan and is sent
  data once it is collected by the operator
• similar to space based observing

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The Future?

• Several large projects in the planning (but
  mostly unfunded stage)
• CELT (California Extremely Large Telescope)
• GSMT (Giant Segmented Mirror Telescope)
• GMT (Giant Magellan Telescope)
• OWL (Overwhelmingly Large Telescope)

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GMT(Giant Magellan Telescope)

• 25.3 meter 7x8.4 meters

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CELT 30 meter(California Extremely Large
Telescope)
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NNTT
National New Technology Telescope
CANCELLED! in 1987 later became the Gemini
Telescopes
a 25 meter telescope project for NOAO
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Some Observations

• Prior to the 80s, when a new telescope was
  built, it often included several smaller
  telescopes
• KPNO CTIO have a multitude of small telescopes
• Now projects (e.g. Gemini) build only large
  telescopes
• many smaller telescopes are being shut down or
  sold to fund the large telescopes
• The amount of collecting area per capita is
  rising rapidly
• The number of available focal planes per capita
  is falling rapidly
• Astronomy is becoming Big Science

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CTIO 60s 70s
Gemini late 90s
KPNO 60s 70s
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Some Observations

• Despite the creation of a national observatory,
  ground based optical/IR telescopes are
  predominantly privately funded and owned
• as of 2002, only 22 of the collecting area is
  available nationally
• new telescopes being built and planned will only
  exacerbate this
• The role of the observational astronomer has
  become that of planner and data analyst
• fewer and fewer observations are being carried
  out by the astronomer
• the construction of telescopes and instruments
  has been handed off to engineers and managers

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Recommended Reading

• Giant Telescopes
• a book by W. Patrick McCray
• Can Remote Observing be Good Observing?
• an essay by Felix Lockman
• paper available on the web at http//arxiv.org/PS
  _cache/astro-ph/pdf/0507/0507140.pdf
  (a.k.a. astro-ph/0507140)