We present an empirical analysis of the effectiveness of frame selection (also known as Lucky Imaging) techniques for high resolution imaging. A high-speed image recording system has been used to observe a number of bright stars. The observations were made over a wide range of values of D/r0 and exposure time. The improvement in Strehl ratio of the stellar images due to aligning frames and selecting the best frames was evaluated as a function of these parameters. We find that improvement in Strehl ratio by factors of 4 to 6 can be achieved over a range of D/r0 from 3 to 12, with a slight peak at D/r0 ~ 7. The best Strehl improvement is achieved with exposure times of 10 ms or less but significant improvement is still obtained at exposure times as long as 640 ms. Our results are consistent with previous investigations but cover a much wider range of parameter space. We show that Strehl ratios of >0.7 can be achieved in appropiate conditions whereas previous studies have generally shown maximum Strehl ratios of ~0.3. The results are in reasonable agreement with the simulations of Baldwin et al. (2008).
Lucky imaging is a technique for high resolution astronomical imaging at visible wavelengths, utilising medium sized ground based telescopes in the 2--4m class. The technique uses high speed, low noise cameras to record short exposures which may then be processed to minimise the deleterious effects of atmospheric turbulence upon image quality. The key statement of this thesis is as follows; that lucky imaging is a technique which now benefits from sufficiently developed hardware and analytical techniques that it may be effectively used for a wide range of astronomical imaging purposes at mediu…
Lucky imaging is a high-resolution astronomical image recovery technique with two classic implementation algorithms, i.e. image selecting, shifting and adding in image space and data selecting and image synthesizing in Fourier space. This paper proposes a novel lucky imaging algorithm where with space-domain and frequency-domain selection rates as a link, the two classic algorithms are combined successfully, making each algorithm a proper subset of the novel hybrid algorithm. Experimental results show that with the same experiment dataset and platform, the high-resolution image obtained by the…
Presented here is list of 50 pairs quasi-evenly spaced over the northern sky, and that have Separations and Position Angles accurate at the milli-arcsec, and milli-degree level. These pairs are suggested as calibration pairs for lucky imaging observations. This paper is a follow-up to our previous paper regarding southern sky calibration pairs.
Accurate measures of double stars require accurate calibration of the instrument. Here we present a list of 50 pairs, that are quasi-evenly spaced over the southern sky, and that have Separations and Position Angles accurate at the milli-arcsec, and milli-degree level. These wide angle pairs are suggested as calibration pairs for lucky imaging observations.
In traditional lucky imaging (TLI), many consecutive images of the same scene are taken with a high frame-rate camera, and all but the sharpest images are discarded before constructing the final shift-and-add image. Here we present an alternative image analysis pipeline -- The Thresher -- for these kinds of data, based on online multi-frame blind deconvolution. It makes use of all available data to obtain a best estimate of the astronomical scene in the context of reasonable computational limits; it does not require prior estimates of the point-spread functions in the images, or knowledge of p…
Lucky Spectroscopy, an equivalent technique to Lucky Imaging. Spatially resolved spectroscopy of massive close visual binaries using the William Herschel Telescope
许多大质量恒星都有邻近的伴星，它们的存在妨碍了光谱学对它们的表征。目的：我们希望获得空间分辨光谱的近距离大质量的视觉双星，以获得他们的光谱类型。方法：我们获得了大量的短长缝光谱曝光的五个紧密的双星在良好的观看条件下，选择那些具有最好的特性，使用多轮廓拟合提取光谱，并结合结果，得到空间分离的光谱。研究结果：我们通过呈现每个系统的组分的空间分辨光谱来证明幸运光谱的有用性，在两种情况下，分离仅为~0.3”。这些是delta Ori Aa+Ab（首次在光学中解析）和sigma Ori AaAb+B（首次解析）。我们还在空间上解决了15 Mon AaAb+B，zeta Ori AaAb+B（以前都解决了GOSSS，银河系O星光谱调查），和eta Ori AaAb+B，一个系统，两个光谱B+B二进制和第五个视觉组件。这两个系统的共同点是，它们都是由一对内部的慢转子组成，一个或多个快转子围绕着它们运行，这一特征可能会对大质量恒星形成理论产生影响。
We recently proposed a new lucky imaging technique, the Power Spectrum Extended (PSE), adapted for image reconstruction of short-exposure astronomical images in case of weak turbulence or partial adaptive optics correction. In this communication we show applications of this technique to observations of about 30 binary stars in H band with the 1m telescope of the Calern C2PU observatory. We show some images reconstructed at the diffraction limit of the telescope and provide measurements of relative astrometry and photometry of observed couples.
Radio interferometry is the current method of choice for deep space astronomy, but in the past few decades optical techniques have become increasingly common. This research seeks to characterize the performance of aperture masking interferometry in the near-infrared at small scales. A mask containing six pairs of apertures at varying diameters and separations was constructed for use with a 24-inch telescope at the MIT Wallace Astrophysical Observatory. Test images of Spica and Jupiter were captured for 28 different telescope configurations, varying aperture separation, aperture diameter, colle…
The Speckle Imager via MUlti Layer Atmospheric Turbulence Object Reconstructor (SIMULATOR) is a lab-based testbed instrument developed to test for speckle correlation-based techniques in the optical regime. However, this instrument can be used as a testbed against post-processing techniques or algorithms like lucky imaging, phase diversity method etc. The SIMULATOR can emulate 3D atmospheric turbulence behaviour using a three-layer turbulence screen, giving the user command over important site characteristics like wind profile, global fried parameter, global isoplanatic patch, mid-layer and hi…
Phase-shifting technique for improving the imaging capacity of sparse-aperture optical interferometers
在本文中，我们描述了一个多孔径干涉仪的原理，使用相移技术，并适用于快速，快照成像的天体物理对象在极端的角分辨率通过傅立叶反演。所提出的设计的几个优点突出，其中包括辐射效率，领域的Fizeau干涉仪，和一个初步的校准程序，允许表征仪器误差。对于大的望远镜数量，所提出的设计也导致在相当大的简化的光学和机械设计。数值模拟表明，仅使用传统光学组件或新兴技术，就可以将数百台望远镜耦合到单个4K x 4K探测器阵列上。
