Least-squares fitting of Gaussian spots on graphics processing units

The investigation of samples with a spatial resolution in the nanometer range relies on the precise and stable positioning of the sample. Due to inherent mechanical instabilities of typical sample stages in optical microscopes, it is usually required to control and/or monitor the sample position during the acquisition. The tracking of sparsely distributed fiducial markers at high speed allows stabilizing the sample position at millisecond time scales. For this purpose, we present a scalable fitting algorithm with significantly improved performance for two-dimensional Gaussian fits as compared to Gpufit.

Temporal Feature Networks for CNN based Object Detection

For reliable environment perception, the use of temporal information is essential in some situations. Especially for object detection, sometimes a situation can only be understood in the right perspective through temporal information. Since image-based object detectors are currently based almost exclusively on CNN architectures, an extension of their feature extraction with temporal features seems promising. Within this work we investigate different architectural components for a CNN-based temporal information extraction. We present a Temporal Feature Network which is based on the insights gained from our architectural investigations. This network is trained from scratch without any ImageNet information based pre-training as these images are not available with temporal information. The object detector based on this network is evaluated against the non-temporal counterpart as baseline and achieves competitive results in an evaluation on the KITTI object detection dataset.

Using raytracing to derive the expected performance of STELLAs SES-VIS spectrograph

The visual STELLA echelle spectrograph (SES-VIS) is a new instrument for the STELLA-II telescope at the Iza~na observatory on Tenerife. Together with the original SES spectrograph - which will still be used in the near IR - and a new H&K-optimized spectrograph, which is currently in the design phase, it will extend the capabilities of STELLA with the follow up of planetary candidates from space missions (TESS, PLATO2). SES-VIS is optimized for precise radial velocity determinations and long term stability. We have developed a ZEMAX based software package to create simulated spectra, which are then extracted using our new data reduction package developed for the PEPSI spectrograph. The focus in this paper has been put on calibration spectra, and the full range of available calibration sources (flat field, Th-Ar, and Fabry-Perot etalon), which can be compared to actual commissioning data once they are available. Furthermore we tested for the effect of changes of the environmental parameters to the wavelength calibration precision.

Second generation spectroscopic instrumentation for the STELLA robotic observatory

The current STELLA Echelle spectrograph (SES), which records 390nm to 870nm in one shot at a spectral resolution of 55000, will be replaced by a suite of specialized spectrographs in three spectral bands. The UV will be covered by a newly designed H&K spectrograph covering 380nm to 470nm (SES-H&K), the visual band (470nm - 690nm) will be covered by SES-VIS, which is a vacuum-stabilized spectrograph designed for high radial-velocity accuracy, and the NIR will be covered by the current SES spectrograph from 690nm to 1050nm. In order to improve the UV transmission, and to accommodate three different fibre-feeds, the prime focus corrector of the telescope will be refurbished, leading to an optical system with the f/2 1200mm spherical primary, a 4-lens collimator with 2 arcsec aperture, atmospheric dispersion corrector (ADC), and two dichroic beam splitters, feeding 3 separate fibre feeds for the three bands. The newly designed H&K spectrograph will be an Echelle spectrograph, based on a R4-grating with 41.6 l/mm and 110mmx420mm, using a f/5 camera and the cross-disperser in double pass (as in TRAFICOS, MIKE, KPF), using 21 spectral orders. The spectral resolution of all three spectrographs will be comparable to the 55000 of the current SES.

On the binary orbit of Henry Draper one (HD 1)

We present our final orbit for the late-type spectroscopic binary HD 1. Employed are 553 spectra from 13 years of observations with our robotic STELLA facility and its high-resolution echelle spectrograph SES. Its long-term radial-velocity stability is $approx$50m/s . A single radial velocity of HD 1 reached a rms residual of 63m/s, close to the expected precision. Spectral lines of HD 1 are rotationally broadened with $vsin i$ of 9.1$pm$0.1 km/s . The overall spectrum appears single-lined and yielded an orbit with an eccentricity of 0.5056$pm$0.0005 and a semi-amplitude of 4.44km/s . We constrain and refine the orbital period based on the SES data alone to 2318.70$pm$0.32d, compared to 2317.8$pm$1.1d when including the older data set published by DAO and Cambridge/Coravel. Owing to the higher precision of the SES data, we base the orbit calculation only on the STELLA/SES velocities in order not to degrade its solution. We redetermine astrophysical parameters for HD 1 from spectrum synthesis and, together with the new {it Gaia} DR-2 parallax, suggest a higher luminosity than published previously. We conclude that HD 1 is a slightly metal-deficient K0 III-II giant 217 times more luminous than the Sun. The secondary remains invisible at optical wavelengths. We present evidence for the existence of a third component.