Astronomy

How does the Large Binocular Telescope resolve so well in both orthogonal directions simultaneously?

How does the Large Binocular Telescope resolve so well in both orthogonal directions simultaneously?


We are searching data for your request:

Forums and discussions:
Manuals and reference books:
Data from registers:
Wait the end of the search in all databases.
Upon completion, a link will appear to access the found materials.

The Forbes article Ask Ethan: How Does Very-Long-Baseline Interferometry Allow Us To Image A Black Hole? includes an example of optical interferometry from the Large Binocular Telescope, shown below.

The occultation of Jupiter's moon, Io, with its erupting volcanoes Loki and Pele, as occulted by Europa, which is invisible in this infrared image. The Large Binocular Telescope was able to do this owing to the technique of interferometry. Credit: LBTO

  • related: When will the next series of mutual eclipses of Jupiter's moons begin?

The LBTO consists of only two telescopes 8.4 m (330 inch) wide mirrors, with centres 14.4 m apart, so I would expect to see higher resolution in one direction than the other.

However in this GIF the resolution seems to be the same in both directions. While I see high spatial frequency ringing in the horizontal direction, I don't see any difference in resolution.

Since the event is so fast (probably minutes or seconds) there is no chance that the natural rotation of the baseline during the course of a night could have helped.

So I'd like to ask How does the Large Binocular Telescope resolve so well in both orthogonal directions simultaneously?


Open image in new window for full size:

Source

The LBTI (green structure in the center of the frame) between the two 8.4m mirrors of the LBT. High resolution image Credit: LBTO - Enrico Sacchetti


The simple answer is that it isn't resolving in both orthogonal directions equally well. The horizontal dimension is the binocular dimension, and from looking at your animation, it looks to have about ~3 times the resolution. The horizontal banding, I'm pretty sure is not ringing, and is in fact, representative of additional information.

This article does a nice job of explaining what is being seen, and it has a picture, both of a simulated depiction of Io from one of the two telescope mirrors, and the combined image. The thing you should notice from the above image is that the 8.4 m telescope picture is at the same resolution as the vertical axis of your animation.

What is going on with the interferometer image?

By increasing the separation between telescopes, we increase the angular resolution. Just about everyone with a casual interest in astronomy will have learned that fact in this past week.

But the other thing you do, is introduce interference patterns. The two telescopes essentially act like a double slit experiment. In the vertical (non binocular) dimension, the diffraction can be treated like a single-slit experiment. The angular intensity formula for a single slit is as follows: $$ I( heta) = I_0 sinc^2(frac{pi b sin( heta)}{lambda})$$ where $b$ is the diameter of each mirror, and $lambda$ is the wavelength of the light.

The horizontal (binocular) dimension acts as a double slit. The double slit formula is as follows: $$ I( heta) = I_0 cos^2(frac{pi d sin( heta)}{lambda})sinc^2(frac{pi b sin( heta)}{lambda})$$ where $d$ is the distance between the centres of the two telescopes.

When you combine these two together, using the telescopes dimensions that you quotes (b=8.4, d=14.4), you come up with a pattern remarkably close to what you actually see from the telescope.

On the left, screencapture from above animation, on the right, the predicted double slit intensity.

Fringe removal

It seems that the animation you saw is based off unprocessed images from the LBT. Obviously, they have methods for removing the fringe bands. As to how, I have no idea. I found a paper that discusses interferometry in depth and they mention:

What we therefore have is a series of fringes, whose amplitude is given by the Fourier transform of the source intensity distribution. In practice, steps are usually taken to get rid of the fringes using a phase rotation whose rate is known (as both B and s are known). This is done in optical interferometers by use of accurate delay lines to compensate for the path difference, and in radio interferometers by the insertion of electronic delays.

But I have no idea what that means. Perhaps some boffin from Physics.SE would be nice enough to answer.


Binoculars

Binoculars or field glasses are two refracting telescopes mounted side-by-side and aligned to point in the same direction, allowing the viewer to use both eyes (binocular vision) when viewing distant objects. Most binoculars are sized to be held using both hands, although sizes vary widely from opera glasses to large pedestal-mounted military models.

Unlike a (monocular) telescope, binoculars give users a three-dimensional image: each eyepiece presents a slightly different image to each of the viewer's eyes and the parallax allows the visual cortex to generate an impression of depth.


How does the Large Binocular Telescope resolve so well in both orthogonal directions simultaneously? - Astronomy

2550), including the polishable surface (but not the polishing itself), that greatly reduces cost and schedule compared to traditional manufacturing and (2) to design a manufacturing facility that optimises the new manufacturing process.

1m scale. With this in view, we first report on form-correction on a smaller analogue of the IRP1200: an IRP400 in service in industry. We then report on the design, commissioning and preliminary process-development results from the first of the scaled-up 1.2m capacity CNC polishing machine from Zeeko, Ltd. This machine delivers the 'Classic' bonnet-based process, together with two new processes: fluid-jet polishing and the hybrid soft-grinding/polishing process called 'Zeeko-Grolish.' We indicate how this trio of processes running on the same machine platform with unified software can provide an unprecedented dynamic range in both volumetric removal rate and removal spot-size. This leads into a discussion of how these processes may be brought to bear on optimal control of texture and form. Preliminary performance of the 1.2m machine is illustrated with results on both axially-symmetric and more complex removal regimes. The paper concludes with an overview of the relevance of the technology to efficient production of instrumentation-optics, space optics and segmented telescope mirrors.

1 micron. Here, we present a departure from these traditional methods and employ the advantages inherent in integrated circuit fabrication. By starting with a silicon wafer, we begin with a nearly atomically flat surface. In addition, the fabrication tools and methodologies employed are traditionally used for high precision applications: this allows for the placement and definition of the slit with high accuracy. If greater accuracy in slit definition is required, additional tools, such as a focused ion beam, are used to define the slit edge down to tens of nanometers. The deposition of gold, after that of a suitable bonding layer, in an ultra-high vacuum chamber creates a final surface without the need of polishing. Typical results yield a surface RMS-roughness of approximately 2nm. Most of the techniques and tools required for this process are commonly available at research universities and the cost to manufacture said mirrors is a small fraction of the purchase price of the traditional ones.

6 K. The main requirements for its three wheel mechanisms include: (1) reliability, (2) optical precision, (3) low power dissipation, (4) high vibration capability, (5) functionality at 4 Show Abstract

80 K in the L2 orbit. In order to reduce the effects of the remaining high thermal background on the sensitive far infrared detectors (60..210 μm), a focal plane chopper is a vital element in the entrance optics of the imaging and spectroscopic instrument PACS. A gold coated 32 × 26 mm 2 plane mirror, suspended by two flexural pivots and driven by a linear motor, allows for precise square wave chopping with up to 9° throw at a frequency 10 Hz with a position accuracy of 1 arcmin. The power required at T

4 K is about 1 mW. The chopper has undergone an extensive qualification programme, including 650 million cold chop throws, 15 cold-warm-cold thermal cycles, 3-axis 26 G-vibration at T

4 K etc. Five models were built and thoroughly tested the flight model of the chopper is now integrated into the flight model of PACS, ready for the HERSCHEL/PLANCK launch in 2008 by an ARIANE5 rocket and the following 5-year mission.

-100°C) and over the operational elevation angle range. We briefly describe the heirarchical design approach for the LSST Camera focal plane and the baseline design for assembling the flat focal plane at room temperature. Preliminary results of gravity load and thermal distortion calculations are provided, and early metrological verification of candidate materials under cold thermal conditions are presented. A detailed, generalized method for stitching together sparse metrology data originating from differential, non-contact metrological data acquisition spanning multiple (non-continuous) sensor surfaces making up the focal plane, is described and demonstrated. Finally, we describe some in situ alignment verification alternatives, some of which may be integrated into the camera's focal plane.

5000. The instrument consists of a central structure and three prism cross-dispersed echelle spectrographs optimized for the UV-blue, visible and near-IR wavelength ranges. The design of the near-IR arm of the X-shooter instrument employs advanced design methods and manufacturing techniques. Integrated system design is done at cryogenic working temperatures, aiming for an almost alignment-free integration. ASTRON Extreme Light Weighting is used for high stiffness at low mass. Bare aluminium is post-polished to optical quality mirrors, preserving high shape accuracy at cryogenic conditions. Cryogenic optical mounts compensate for CTE differences of various materials, while ensuring high thermal contact. This paper addresses the general design and the application of these specialized techniques.

5000, and will provide a very wide simultaneous spectral coverage, ranging from 320 to 2500 nm. The instrument consists in a central structure which supports three prism cross-dispersed echelle spectrographs respectively optimized for the UV-blue, Visible and Near-IR wavelength ranges. X-shooter will offer an image slicer based Integral Field Unit (IFU) designed to analyse a 1.8"x4" input field into 3 slices of 0.6"x4"and to align then on a 12" long slit. The principle of the IFU is that the central slice does not include any dioptre, the light is directly transmitted to the spectrographs. Only the two lateral sliced fields are reflected toward the two pairs of spherical mirrors and re-aligned at both ends of the previous slice in order to form the exit slit. We present here the IFU design developed at the Observatoire de Paris.


Watch the video: Two Eyes are better than one - Binocular Observing (May 2022).