The 1.6m New Solar Telescope (NST) has developed a modern and comprehensive suite of instruments which allow high resolution observations of the Sun. The current instrument package comprises diffraction limited imaging, spectroscopic and polarimetric instruments covering the wavelength range from 0.4 to 5.0 microns. The instruments include broadband imaging, visible and near-infrared scanning Fabry-Perot interferometers, an imaging spectropolarimeter, a fast visible-light imaging spectrograph, and a unique new scanning cryogenic infrared spectrometer/spectropolarimeter that is nearing completion. Most instruments are operated with a 308 subaperture adaptive optics system, while the thermal-IR spectrometer has a correlation tracker. This paper reports on the current observational programs and operational performance of the telescope and instrumentation. The current control, data processing, and archiving systems are also briefly discussed.

IRIM (Infrared Imaging Magnetograph) is one of the first imag- ing solar spectro-polarimeters working in the near infrared (NIR). IRIM is be- ing installed and commissioned in the Coude Lab of the 1.6-meter New Solar Telescope (NST) at Big Bear Solar Observatory (BBSO). This innovative sys- tem, which includes a 2.5 nm interference filter, a unique 0.25 nm birefringent Lyot filter, and a Fabry-Perot etalon, is capable of providing a bandpass as low as 0.01 nm over a field-of-view of 50 '' in a telecentric configuration. An NIR waveplate rotates ahead of M3 in the NST as the polarimeter modulator, and ahead of it locates a calibration unit to reduce polarization cross-talk induced by subsequent oblique mirrors. Dual-beam differential polarimetry is employed to minimize seeing-induced spurious polarization. Based on the unique advantages in IR window, the very capable NST with adaptive optics, IRIM will provide unprecedented solar spectro-polarimetry with high Zeeman sensitivity (10 −3 Ic), high spatial resolution (0:2 '' ), and high cadence (15 s). In this paper, we discuss the design, fabrication, and calibration of IRIM, as well as the results of the first light observations.

The NST (New Solar Telescope), a 1.6 m clear aperture, off-axis telescope, is in its commissioning phase at Big Bear Solar Observatory (BBSO). It will be the most capable, largest aperture solar telescope in the US until the 4 m ATST (Advanced Technology Solar Telescope) collies on-line late in the next decade. The NST will be outfitted with state-of-the-art scientific instruments at the Nasmyth focus on the telescope floor and in the Coude Lab beneath the telescope. At the Nasmyth focus, several filtergraphs already in routine operation have offered high spatial resolution photometry in TiO 706 nm, H alpha 656 nm, G-band 430 nm and the near infrared (NIR), with the aid of a correlation tracker and image reconstruction system. Also, a Cryogenic Infrared Spectrograph (CYRA) is being developed to supply high signal-to-noise-ratio spectrometry and polarimetry spanning 1.0 to 5.0 mu m. The Coude Lab instrumentation will include Adaptive Optics (AO), InfraRed imaging Magnetograph (IRIM), Visible Imaging Magnetograph (VIM), and Fast imaging Solar Spectrograph (FISS). A 308 sub-aperture (349-actuator deformable mirror) AO system will enable nearly diffraction limited observations over the NST's principal operating wavelengths from 0.4 mu m through 1.7 mu m. IRIM and VIM are Fabry-Perot based narrow-band tunable filters, which provide high resolution two-dimensional spectroscopic and polarimetric imaging in the NIR and visible respectively. FISS is a collaboration between BBSO and Seoul National University focussing on chromosphere dynamics. This paper reports the up-to-date progress on these instruments including an overview of each instrument and details of the current state of design, integration, calibration and setup/testing on the NST. (C) 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

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 Ha 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 or 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 Hats. The focal ratio of the primary mirror is f/2.4. The working wavelength range covers from 0.4 to 1.7 mu m in the Coude Lab beneath the telescope and all wavelengths including the far infrared at the Nasmyth focus on the dome floor. (C) 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

The New Solar Telescope (NST) is a 1.6-meter off-axis Gregory-type telescope with an equatorial mount and an open optical support structure. To mitigate the temperature fluctuations along the exposed optical path, the effects of local/dome-related seeing have to be minimized. To accomplish this, NST will be housed in a 5/8-sphere fiberglass dome that is outfitted with 14 active vents evenly spaced around its perimeter. The 14 vents house louvers that open and close independently of one another to regulate and direct the passage of air through the dome. In January 2006, 16 thermal probes were installed throughout the dome and the temperature distribution was measured. The measurements confirmed the existence of a strong thermal gradient on the order of 5° Celsius inside the dome. In December 2006, a second set of temperature measurements were made using different louver configurations. In this study, we present the results of these measurements along with their integration into the thermal control system (ThCS) and the overall telescope control system (TCS).

The New Solar Telescope (NST) project at Big Bear Solar Observatory (BBSO) now has all major contracts for design and fabrication in place and construction of components is well underway. NST is a collaboration between BBSO, the Korean Astronomical Observatory (KAO) and Institute for Astronomy (IfA) at the University of Hawaii. The project will install a 1.6-meter, off-axis telescope at BBSO, replacing a number of older solar telescopes. The NST will be located in a recently refurbished dome on the BBSO causeway, which projects 300 meters into the Big Bear Lake. Recent site surveys have confirmed that BBSO is one of the premier solar observing sites in the world. NST will be uniquely equipped to take advantage of the long periods of excellent seeing common at the lake site. An up-to-date progress report will be presented including an overview of the project and details on the current state of the design. The report provides a detailed description of the optical design, the thermal control of the new dome, the optical support structure, the telescope control systems, active and adaptive optics systems, and the post-focus instrumentation for high-resolution spectro-polarimetry.

A long-standing solar problem has been to measure the coronal magnetic field. We believe it determines the coronal structure and dynamics from the upper chromosphere out into the heliospheric environment. It is only recently that Zeeman splitting observations of infrared coronal emission lines have been successfully used to deduce the coronal magnetic flux density. Here we extend this technique and report first results from a novel coronal magnetometer that uses an off-axis reflecting coronagraph and optical fiber-bundle imaging spectropolarimeter. We determine the line-of-sight magnetic flux density and transverse field orientation in a two-dimensional map with a sensitivity of about 1 G with 20" spatial resolution after 70 minutes of integration. These full-Stokes spectropolarimetric measurements of the forbidden Fe XIII 1075 nm coronal emission line reveal the line-of-sight coronal magnetic field 100" above an active region to have a flux density of about 4 G.

A 0.5m aperture off-axis coronagraphic telescope is described. Its fabrication, imaging, and scattered light performance is discussed in the context of simple model expectations.

A new generation of off-axis telescopes has been proposed to address a number of high dynamic range problems in astrophysics. These systems present unusual problems and opportunities for the instrument designer. We will discuss some of the issues that must be resolved when placing instrumentation at the prime focus. The heat stop and occulter systems for the SOLAR-C Off-axis Coronagraph will be used to illustrate strategies for solar telescope applications.

This paper summarizes concept studies for a large telescope capable of wide-field imaging and of the highest possible dynamic range for photometry and angular resolution.Point-spread functions (PSFs) and scattered light levels at large offsets are computed and compared for four telescopes of the same light-gathering power but with different pupil functions:1. a reference monolithic mirror telescope with a 17.4 m primary,2. a segmented mirror telescope (SMT) with a hexagonally segmented primary,3. a hexagonal off-axis telescope (HOT) with a distributed aperture made of m unobstructed circular 6 x 6.5 mirrors that are identical off-axis sections of a parent 20 m mirror, and4. a square off-axis telescope (SOT) whose aperture is made of m off-axis mirrors. 4 x 8.The characteristics of the PSFs are examined in the diffraction- and seeing-limited regimes, assuming (1) perfect mirror figure and (2) realistic figure errors (edge defects). The implications of field rotation with an altitude-azimuth mounting are discussed in each case. The implementation of adaptive optics (AO) and the properties of AO-compensated PSFs having a Strehl ratio of 0.5, and of coronagraphic imaging, are also discussed for the four configurations. It is shown that, in the seeing-limited regime and as intuitively expected, the optical performance of all four telescopes is comparable. With higher order adaptive optics and for coronagraphic observations, the SOT and HOT are superior to the SMT. This distinction becomes larger with relaxed constraints on mirror edge-polishing requirements. A full optical design is presented for the novel HOT configuration, and optical fabrication issues are briefly addressed. Finally, science programs and possible instrumentation layouts with the HOT are briefly explored for different modes of operation. It appears that the natural "optical bench" configuration of the HOT can provide a remarkably versatile and convenient environment for instrument deployment.

All existing night-time astronomical telescopes, regardless of aperture, are blind to an important part of the universe - the region around bright objects. Technology now exist to build an unobscured 6.5 m aperture telescope which will attain coronagraphic sensitivity heretofore unachieved. A working group hosted by the University of Hawaii Institute for Astronomy has developed plans for a New Planetary Telescope which will permit astronomical observations which have never before ben possible. In its narrow-field mode the off-axis optical design, combined with adaptive optics, provides superb coronagraphic capabilities, and a very low thermal IR background. These make it ideal for studies of extra-solar planets and circumstellar discs, as well as for general IR astronomy. In its wide-field mode the NPT provides a 2 degree diameter field for surveys of Kuiper Belt Objects and Near-Earth Objects, surveys central to current intellectual interests in solar system astronomy.

We report here the probable detection of an emission line of Si IX that was observed from an open C130 aircraft over the Pacific Ocean during the 1998 total solar eclipse. Although the IR data themselves are inconclusive because of the uncertainty in the precise central wavelengths of the narrowband filters during the eclipse, the consistency of the measured IR limb excess with simultaneous EUV emission measured by SOHO/Coronal Diagnostic Spectrometer and the EUV Imager Telescope support our detection claim. This line appears to be the brightest IR coronal line yet observed, and its existence may significantly improve future prospects for obtaining optical coronal magnetic field measurements.

New full-disk satellite and ground-based experiments operating at visible wavelengths can routinely produce solar photometric data of sufficient accuracy to directly observe the photospheric signature of total irradiance variations. Such data are likely to directly test causal (as opposed to statistical) models of the irradiance mechanisms. This is an important step, since without a physical understanding of these changes we can neither predict nor rule out the possibility of future (or past) large solar influences on the earth's climate variability.

Helioseismic and precise solar photometric measurements reveal that the Sun varies globally as a start during the source of an 11 year solar cycle. To understand the physical mechanisms of the magnetic cycle in the solar interior we must learn how to measure the tiny changes in the Sun's global properties, like its radius, internal temperature distribution and surface luminosity. The SoHO/MDI experimental has proven that exceedingly small solar shape fluctuations are measurable from outside our atmosphere. We describe here an instrument which will not only measure limb shape oscillations with unprecedented accuracy, but it will also detect solar radius changes with heretofore unachieved accuracy and precision. Variations in these parameters are caused by physical changes, both in the photosphere and the deep solar interior. Solar radius and shape observations will teach us how the Sun's convective envelope responds to emergent energy fluctuations. The determination of this outer boundary condition is essential to understand the solar total irradiance and luminosity variations.

The RISE/PSPT (‘Radiative Inputs from the Sun to the Earth/Precision Solar Photometric Telescopes’) experiment will attain high differential photometric precision in full-disk solar images with 1 arc sec pixels. To achieve this spatial resolution it will be necessary to use frame selection techniques to minimize the effects of atmospheric ‘seeing’. We report here on experiments to use a simple scintillation monitor as a trigger or ‘veto’ for imaging observations.