A Two-Colour CCD Survey of the North Celestial Cap: I. The Method

We describe technical aspects of an astrometric and photometric survey of the North Celestial Cap (NCC), from the Pole (DEC=90 deg) to DEC=80 deg, in support of the TAUVEX mission. This region, at galactic latitudes from ~ 17 deg to ~ 37 deg, has poor coverage in modern CCD-based surveys. The observations are performed with the Wise Observatory one-meter reflector and with a new mosaic CCD camera (LAIWO) that images in the Johnson-Cousins R and I bands a one-square-degree field with subarcsec pixels. The images are treated using IRAF and SExtractor to produce a final catalogue of sources. The astrometry, based on the USNO-A2.0 catalogue, is good to ~ 1 arcsec and the photometry is good to ~ 0.1 mag for point sources brighter than R=20.0 or I=19.1 mag. The limiting magnitudes of the survey, defined at photometric errors smaller than 0.15 mag, are 20.6 mag (R) and 19.6 (I). We separate stars from non-stellar objects based on the object shapes in the R and I bands, attempting to reproduce the SDSS star/galaxy dichotomy. The completeness test indicates that the catalogue is complete to the limiting magnitudes.Comment: 31 pages, 15 figures, Accepted for publication in Astrophysics & Space Scienc

An Improved Photometric Calibration of the Sloan Digital Sky Survey Imaging Data

We present an algorithm to photometrically calibrate wide field optical imaging surveys, that simultaneously solves for the calibration parameters and relative stellar fluxes using overlapping observations. The algorithm decouples the problem of "relative" calibrations, from that of "absolute" calibrations; the absolute calibration is reduced to determining a few numbers for the entire survey. We pay special attention to the spatial structure of the calibration errors, allowing one to isolate particular error modes in downstream analyses. Applying this to the Sloan Digital Sky Survey imaging data, we achieve ~1% relative calibration errors across 8500 sq.deg. in griz; the errors are ~2% for the u band. These errors are dominated by unmodelled atmospheric variations at Apache Point Observatory. These calibrations, dubbed "ubercalibration", are now public with SDSS Data Release 6, and will be a part of subsequent SDSS data releases.Comment: 16 pages, 17 figures, matches version accepted in ApJ. These calibrations are available at http://www.sdss.org/dr

Seoul National University Camera II (SNUCAM-II): The New SED Camera for the Lee Sang Gak Telescope (LSGT)

We present the characteristics and the performance of the new CCD camera system, SNUCAM-II (Seoul National University CAMera system II) that was installed on the Lee Sang Gak Telescope (LSGT) at the Siding Spring Observatory in 2016. SNUCAM-II consists of a deep depletion chip covering a wide wavelength from 0.3 {\mu}m to 1.1 {\mu}m with high sensitivity (QE at > 80% over 0.4 to 0.9 {\mu}m). It is equipped with the SDSS ugriz filters and 13 medium band width (50 nm) filters, enabling us to study spectral energy distributions (SEDs) of diverse objects from extragalactic sources to solar system objects. On LSGT, SNUCAM-II offers 15.7 {\times} 15.7 arcmin field-of-view (FOV) at a pixel scale of 0.92 arcsec and a limiting magnitude of g = 19.91 AB mag and z=18.20 AB mag at 5{\sigma} with 180 sec exposure time for point source detection.Comment: 8 pages, 9 figures, 4 tables, published in 2017 June issue of JKA

Depth Fields: Extending Light Field Techniques to Time-of-Flight Imaging

A variety of techniques such as light field, structured illumination, and time-of-flight (TOF) are commonly used for depth acquisition in consumer imaging, robotics and many other applications. Unfortunately, each technique suffers from its individual limitations preventing robust depth sensing. In this paper, we explore the strengths and weaknesses of combining light field and time-of-flight imaging, particularly the feasibility of an on-chip implementation as a single hybrid depth sensor. We refer to this combination as depth field imaging. Depth fields combine light field advantages such as synthetic aperture refocusing with TOF imaging advantages such as high depth resolution and coded signal processing to resolve multipath interference. We show applications including synthesizing virtual apertures for TOF imaging, improved depth mapping through partial and scattering occluders, and single frequency TOF phase unwrapping. Utilizing space, angle, and temporal coding, depth fields can improve depth sensing in the wild and generate new insights into the dimensions of light's plenoptic function.Comment: 9 pages, 8 figures, Accepted to 3DV 201

Optical Synoptic Telescopes: New Science Frontiers

Over the past decade, sky surveys such as the Sloan Digital Sky Survey have proven the power of large data sets for answering fundamental astrophysical questions. This observational progress, based on a synergy of advances in telescope construction, detectors, and information technology, has had a dramatic impact on nearly all fields of astronomy, and areas of fundamental physics. The next-generation instruments, and the surveys that will be made with them, will maintain this revolutionary progress. The hardware and computational technical challenges and the exciting science opportunities are attracting scientists and engineers from astronomy, optics, low-light-level detectors, high-energy physics, statistics, and computer science. The history of astronomy has taught us repeatedly that there are surprises whenever we view the sky in a new way. This will be particularly true of discoveries emerging from a new generation of sky surveys. Imaging data from large ground-based active optics telescopes with sufficient etendue can address many scientific missions simultaneously. These new investigations will rely on the statistical precision obtainable with billions of objects. For the first time, the full sky will be surveyed deep and fast, opening a new window on a universe of faint moving and distant exploding objects as well as unraveling the mystery of dark energy.Comment: 12 pages, 7 figure