Mr. Doug Gray Profile

Doug Gray

at Australian Astronomical Observatory

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Author

Publications (6)

Proceedings Article | 10 July 2018 Presentation

A new sky subtraction optimised flat field calibration system for the 3.9m Anglo-Australian telescope (Conference Presentation)

Anthony Horton, Chris Lidman, Doug Gray, Pascal Xavier

Proceedings Volume 10704, 107041N (2018) https://doi.org/10.1117/12.2313343

KEYWORDS: Calibration, Telescopes, Astronomical imaging, Spectrographs, Domes, Surface conduction electron emitter displays, Lamps, Astronomy, Optical fibers, Stray light

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Given enough exposure time the sensitivity of an astronomical instrument is ultimately limited by systematic errors, and the dominant source of systematic errors for most optical/infrared instruments is imperfect sky subtraction. In turn the limiting factor for sky subtraction accuracy is frequently the accuracy of flat field calibration, making these calibrations critical to the overall performance of the instrument. The Anglo-Australian Telescope’s fibre-fed spectrographs, and in particular the multi-object integral field spectrograph SAMI, are reaching sky subtraction systematic error limits and this has motivated an upgrade to the calibration systems. SAMI and its successor HECTOR are calling for sky subtraction accuracies of at least 0.25%, with a goal of 0.06%, an improvement of 4-17 times. Flat field calibrations can use dark sky, twilight sky or an illuminated screen (‘dome flats’). For multi-object spectrographs such as SAMI recalibration is required for each set of targets. This makes twilight flats impractical as it is impossible to guarantee the availability of clear twilight sky for every configuration. The dark night sky is the ideal calibrator, but the long integration times required result in onerous overheads. What is needed is a dome flat field system accurate enough to replace dark sky flats. To achieve this we have replaced both the existing screen and its illumination system. The effective throughput of optical fibres feeding an instrument vary slightly as their paths change, so high accuracy demands that calibration be done with the telescope in the same position as the science observations. We have applied two new screens to the dome windscreen, either side of the aperture, so that it is possible to move a screen in front of the telescope while in any position. There are two distinct purposes for flat fielding: photometric calibration and sky subtraction. For an ideal telescope these are equivalent but the existence of stray light creates subtle differences, and this has implications for design of the screen. When the primary purpose is sky subtraction the highest possible accuracy will be achieved with a screen that illuminates the telescope from all the directions that the night sky does. Consequently our screens match the size, shape and relative position of the windscreen aperture. The screens are implemented as Avian D diffuse reflectance coating applied to the dome windscreen itself. Avian D is highly Lambertian, has high reflectance and is durable enough for the observatory environment. The screens must be illuminated uniformly, in terms of spatial variations of both total intensity and spectral energy distribution (SED). We use an array of lamps around the end of the telescope tube. By using LEDs we are able to customise the SED and obtain a signal to noise ratio that is more consistent across wavelengths than is possible with traditional quartz tungsten halogen flat field lamps. We present the design of the new flat field calibration system, explain the main design decisions and discuss results from commissioning. These include comparisons between dome and dark sky flats, and measurements of the sky subtraction accuracy.

Proceedings Article | 6 July 2018 Presentation + Paper

Veloce Rosso: Australia's new precision radial velocity spectrograph

James Gilbert, Christoph Bergmann, Gabe Bloxham, Robert Boz, Robert Brookfield, Tom Carkic, Brad Carter, Scott Case, Vladimir Churilov, Michael Ellis, Gaston Gausachs, Luke Gers, Doug Gray, Nicholas Herrald, Michael Ireland, Damien Jones, Yevgen Kripak, Jon Lawrence, Ellie O'Brien, Ian Price, Matthew Robertson, Christian Schwab, Chris Tinney, Annino Vaccarella, Colin Vest, Duncan Wright, Ross Zhelem

Proceedings Volume 10702, 107020Y (2018) https://doi.org/10.1117/12.2312399

KEYWORDS: Spectrographs, Sensors, Control systems, Calibration, Telescopes, Observatories, Optical benches, Relays, Image processing, Astronomy

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Proceedings Article | 6 July 2018 Paper

VELOCE’s novel IFU-fitted fibre feed

Scott Case, Vladimir Churilov, Ross Zhelem, Anthony Horton, Jon Lawrence, Michael Edgar, Tony Farrell, Lewis Waller, Yevgen Kripak, Doug Gray, Christopher Ramage, Steve Lee, Mike Ireland, Christian Schwab, Chris Tinney

Proceedings Volume 10702, 107026E (2018) https://doi.org/10.1117/12.2312939

KEYWORDS: Spectrographs, Calibration, Telescopes, Optical fibers, Beam splitters, Optics manufacturing, Microlens array, Manufacturing, Prototyping

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SPIE Journal Paper | 10 August 2015 Open Access

First light results from the High Efficiency and Resolution Multi-Element Spectrograph at the Anglo-Australian Telescope

Andrew Sheinis, Borja Anguiano Jimenez, Martin Asplund, Carlos Bacigalupo, Samuel Barden, Michael Birchall, Joss Bland-Hawthorn, Jurek Brzeski, Russell Cannon, Daniela Carollo, Scott Case, Andrew Casey, Vladimir Churilov, Warrick Couch, Robert Dean, Gayandhi De Silva, Valentina D’Orazi, Ly Duong, Tony Farrell, Kristin Fiegert, Kenneth Freeman, Gabriella Frost, Luke Gers, Michael Goodwin, Doug Gray, Andrew Green, Ron Heald, Jeroen Heijmans, Michael Ireland, Damien Jones, Prajwal Kafle, Stefan Keller, Urs Klauser, Yuriy Kondrat, Janez Kos, Jon Lawrence, Steve Lee, Slavko Mali, Sarah Martell, Darren Mathews, Don Mayfield, Stan Miziarski, Rolf Muller, Naveen Pai, Robert Patterson, Ed Penny, David Orr, Katharine Schlesinger, Sanjib Sharma, Keith Shortridge, Jeffrey Simpson, Scott Smedley, Greg Smith, Darren Stafford, Nicholas Staszak, Minh Vuong, Lewis Waller, Elizabeth Wylie de Boer, Pascal Xavier, Jessica Zheng, Ross Zhelem, Daniel Zucker, Tomaz Zwitter

JATIS, Vol. 1, Issue 03, 035002, (August 2015) https://doi.org/10.1117/12.10.1117/1.JATIS.1.3.035002

KEYWORDS: Spectrographs, Sensors, Mirrors, Cameras, Collimators, Telescopes, Multi-element lenses, Stars, Control systems, Charge-coupled devices

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Proceedings Article | 8 July 2014 Paper

First light results from the Hermes spectrograph at the AAT

Andrew Sheinis, Sam Barden, Michael Birchall, Daniela Carollo, Joss Bland-Hawthorn, Jurek Brzeski, Scott Case, Russell Cannon, Vladimir Churilov, Warrick Couch, Robert Dean, Gayandhi De Silva, Valentina D'Orazi, Tony Farrell, Kristin Fiegert, Kenneth Freeman, Gabriella Frost, Luke Gers, Michael Goodwin, Doug Gray, Ron Heald, Jeroen Heijmans, Damien Jones, Stephan Keller, Urs Klauser, Yuriy Kondrat, Jon Lawrence, Steve Lee, Slavko Mali, Sarah Martell, Darren Mathews, Don Mayfield, Stan Miziarski, Rolf Muller, Naveen Pai, Robert Patterson, Ed Penny, David Orr, Keith Shortridge, Jeffrey Simpson, Scott Smedley, Greg Smith, Darren Stafford, Nicholas Staszak, Minh Vuong, Lewis Waller, Elizabeth Wylie de Boer, Pascal Xavier, Jessica Zheng, Ross Zhelem, Daniel Zucker

Proceedings Volume 9147, 91470Y (2014) https://doi.org/10.1117/12.2055595

KEYWORDS: Sensors, Spectrographs, Cameras, Control systems, Collimators, Mirrors, Electronics, Charge-coupled devices, Telescopes, Stars

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Proceedings Article | 5 October 2012 Paper

Integrating the HERMES spectrograph for the AAT

Jeroen Heijmans, Martin Asplund, Sam Barden, Michael Birchall, Daniela Carollo, Joss Bland-Hawthorn, Jurek Brzeski, Scott Case, Vladimir Churilov, Matthew Colless, Robert Dean, Gayandhi De Silva, Tony Farrell, Kristin Fiegert, Kenneth Freeman, Luke Gers, Michael Goodwin, Doug Gray, Ron Heald, Anthony Heng, Damien Jones, Chiaki Kobayashi, Urs Klauser, Yuriy Kondrat, Jon Lawrence, Steve Lee, Darren Mathews, Don Mayfield, Stan Miziarski, Guy Monnet, Rolf Muller, Naveen Pai, Robert Patterson, Ed Penny, David Orr, Andrew Sheinis, Keith Shortridge, Scott Smedley, Greg Smith, Darren Stafford, Nicholas Staszak, Minh Vuong, Lewis Waller, Denis Whittard, Elisabeth Wylie de Boer, Pascal Xavier, Jessica Zheng, Ross Zhelem, Daniel Zucker

Proceedings Volume 8446, 84460W (2012) https://doi.org/10.1117/12.925806

KEYWORDS: Sensors, Spectrographs, Stars, Control systems, Device simulation, Cameras, Charge-coupled devices, Electronics, Telescopes, Collimators

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Showing 5 of 6 publications

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