Scanning pentaprism measurements of off-axis aspherics

Su, Peng; Burge, James H.; Cuerden, Brian; Sasián, José M.; Martin, Hubert M.

doi:10.1117/12.789588

Cited by 23 publications

(11 citation statements)

References 4 publications

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“…The origin of this difficulty remained a mystery for more than a year with various solutions being attempted. One useful implementation during this interim was testing/figuring using a pentaprism scan (Su et al 2008), which was fine for characterizing low-order aberrations. Still, from this test alone, we would not know whether or not unacceptable, higher order aberrations were being introduced during the figuring.…”

Section: Nst Issuesmentioning

confidence: 99%

The NST: First results and some lessons for ATST and EST

Goode¹,

Coulter

Gorceix

et al. 2010

Astron Nachr

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In January 2009, first light observations with the NST (New Solar Telescope) in Big Bear Solar Observatory (BBSO) were made. NST has a 1.7 m primary with a 1.6 m clear aperture. First observational results in TiO and Hα are shown and discussed. The NST primary mirror is the most aspheric telescope mirror deployed to date. The NST is early in its commissioning, and the plans for this phase will be sketched. Lessons learned in building and implementing the NST are germane for the ATST and EST telescopes and will be discussed. The NST has an off-axis Gregorian configuration consisting of a parabolic primary, heat-stop, elliptical secondary and diagonal flats. The focal ratio of the primary mirror is f/2.4. The working wavelength range covers from 0.4 to 1.7 μm in the Coudé Lab beneath the telescope and all wavelengths including the far infrared at the Nasmyth focus on the dome floor.

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Section: Nst Issuesmentioning

confidence: 99%

The NST: First results and some lessons for ATST and EST

Goode¹,

Coulter

Gorceix

et al. 2010

Astron Nachr

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“…The Principal Test 12 is used for day-to-day testing to guide polishing of the front surface. Two additional tests, the Laser Tracker Plus Test (LTP) 13,14 and the Pentaprism Test (PT) 13,15 , are sensitive to low-order aberrations (astigmatism, coma, trefoil, spherical aberration, etc.) in the surface and provide two independent verifications of the Principal Test results.…”

Section: Metrologymentioning

confidence: 99%

Progress on the GMT

Johns

2008

SPIE Proceedings

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The Giant Magellan Telescope (GMT) is being developed by a consortium of major US and international educational and research institutions. The 25 meter next-generation telescope will be located at Las Campanas Observatory in Chile. The project has completed the conceptual design of the telescope and enclosure and is currently in the Design Development Phase leading up to construction. Various refinements have been made to the telescope structure since the Conceptual Design. These include the modification of the upper truss structure to reduce image blur due to wind shake and the design of a 9 meter rotator for large Gregorian instruments. An integral field spectrograph has been added to the candidate list of first-generation instruments. The primary mirror for GMT consists of seven 8.4 meter diameter segments. The first of the six, highly aspheric, off-axis segments has been cast and generated at the University of Arizona SOML with completion of the mirror expected in 2009. The metrology for polishing the segments is currently being installed in the new test tower at SOML. Verification tests that independently measure the mirror figure have been designed and are also being implemented. This paper summarizes the overall design and recent progress in the technical development of GMT and in characterizing the site.

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“…To obtain this accuracy with an off-axis mirror, it is necessary to carefully account for field aberrations that result when the collimated beam is not exactly parallel to the optical axis. These effects have been analyzed in previous papers [6], [7] , and the results have been used in testing the 1.7 m off-axis primary mirror of the New Solar Telescope (NST). In this paper, we summarize the principles of the pentaprism test, including the field effects that are important for off-axis mirrors.…”

Section: Introductionmentioning

confidence: 99%

Scanning pentaprism test for the GMT 8.4-m off-axis segments

Allen

Burge

et al. 2010

SPIE Proceedings

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The scanning pentaprism system for testing the 8.4 m off-axis segments for the Giant Magellan Telescope has recently been completed. The system uses a fiber source and a carriage mounted pentaprism to scan a 40 mm collimated beam across the surface of the segment under test. Since the scanning beam is parallel to the optical axis of the parent mirror, it comes to focus on a detector at the telescope's prime focus, where displacement of the spot is proportional to the slope error. A second collimated beam from a stationary reference pentaprism is used to compensate for any changes in the relative positions of the optical components during testing. The optical components are suspended over the mirror on a rail system that can be rotated so that scans can be made across any diameter of the segment. The test is capable of measuring wavefront slope errors to 1 μrad rms, adequate to verify that power, astigmatism, coma, and other low-order aberrations are small enough to be corrected easily at the telescope with the segment's active support system.

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Scanning pentaprism measurements of off-axis aspherics

Cited by 23 publications

References 4 publications

The NST: First results and some lessons for ATST and EST

The NST: First results and some lessons for ATST and EST

Progress on the GMT

Scanning pentaprism test for the GMT 8.4-m off-axis segments

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