scholarly journals TheYBand at 1.035 Microns: Photometric Calibration and the Dwarf Stellar/Substellar Color Sequence

2002 ◽  
Vol 114 (797) ◽  
pp. 708-720 ◽  
Author(s):  
Lynne A. Hillenbrand ◽  
Jonathan B. Foster ◽  
S. E. Persson ◽  
K. Matthews
Keyword(s):  
Photometric Calibration ◽  
Color Sequence

Calibration and Validation of Infrared Sounders with Moon and Mercury

2021 ◽  
Author(s):  
Martin Burgdorf ◽  
Stefan A. Buehler ◽  
Viju John ◽  
Thomas Müller ◽  
Marc Prange
Keyword(s):  
Large Time ◽  
Angular Resolution ◽  
The Moon ◽  
Photometric Calibration ◽  
The Earth ◽  
Spread Function ◽  
Spectral Channels ◽  
Better Than ◽  
Full Disk

<p>Serendipitous observations of airless bodies of the inner solar system provide a unique means to the calibration of instruments on meteorological research satellites, because the physical properties of their surfaces change very little, even on large time scales. We investigated how certain instrumental effects can be characterised with observations of the Moon and Mercury. For this we identified and analysed intrusions of the Moon in the deep space views of HIRS/2, /3, and /4 (High-resolution Infrared Sounder) on various satellites in polar orbits and as well some images obtained with SEVIRI (Spinning Enhanced Visible Infra-Red Imager) on MSG-3 and -4 (Meteosat Second Generation), which had Mercury standing close to the Earth in the rectangular field of view.</p><p>A full-disk, infrared Moon model was developed that describes how the lunar flux density depends on phase angle and wavelength. It is particularly helpful for inter-calibration, checks of the photometric consistency of the sounding channels, and the calculation of an upper limit on the non-linearity of the shortwave channels of HIRS. In addition, we used the Moon to determine the co-registration of the different spectral channels.</p><p>Studies of the channel alignment are also presented for SEVIRI, an infrared sounder with an angular resolution about a hundred times better than HIRS. As we wanted to check the image quality of this instrument with a quasi-point source as well, we replaced here the Moon with Mercury. We found the typical smearing of the point spread function in the scan direction and occasionally a nearby ghost image, which is three to four times fainter than the main image of the planet. Both effects cause additional uncertainties of the photometric calibration.  </p>

Color Sequence Preserving Decolorization

2015 ◽  
Vol 34 (2) ◽  
pp. 373-383 ◽  
Author(s):  
M.-J. Yoo ◽  
I.-K. Lee ◽  
S. Lee
Keyword(s):  
Color Sequence

scholarly journals Analysis of full disc Ca II K spectroheliograms

2018 ◽  
Vol 609 ◽  
pp. A92 ◽  
Author(s):  
Theodosios Chatzistergos ◽  
Ilaria Ermolli ◽  
Sami K. Solanki ◽  
Natalie A. Krivova
Keyword(s):  
Synthetic Data ◽  
Calibration Method ◽  
Poor Quality ◽  
Average Error ◽  
Photometric Calibration ◽  
Solar Observations ◽  
Relative Errors ◽  
Long Term Variations ◽  
The Ideal

Context. Historical Ca II K spectroheliograms (SHG) are unique in representing long-term variations of the solar chromospheric magnetic field. They usually suffer from numerous problems and lack photometric calibration. Thus accurate processing of these data is required to get meaningful results from their analysis. Aims. In this paper we aim at developing an automatic processing and photometric calibration method that provides precise and consistent results when applied to historical SHG. Methods. The proposed method is based on the assumption that the centre-to-limb variation of the intensity in quiet Sun regions does not vary with time. We tested the accuracy of the proposed method on various sets of synthetic images that mimic problems encountered in historical observations. We also tested our approach on a large sample of images randomly extracted from seven different SHG archives. Results. The tests carried out on the synthetic data show that the maximum relative errors of the method are generally <6.5%, while the average error is <1%, even if rather poor quality observations are considered. In the absence of strong artefacts the method returns images that differ from the ideal ones by <2% in any pixel. The method gives consistent values for both plage and network areas. We also show that our method returns consistent results for images from different SHG archives. Conclusions. Our tests show that the proposed method is more accurate than other methods presented in the literature. Our method can also be applied to process images from photographic archives of solar observations at other wavelengths than Ca II K.

scholarly journals BVRI photometric calibration of the Nedeljkovic telescope

2021 ◽  
pp. 3-3
Author(s):  
A. Vudragovic ◽  
M. Jurkovic
Keyword(s):  
Ccd Camera ◽  
Color Correction ◽  
Photometric Calibration ◽  
Astronomical Station

We have done photometric calibration of the 60 cm Nedeljkovic telescope equipped with the FLI PL 230 CCD camera, mounted at the Astronomical Station Vidojevica (Serbia), using standard stars from the Landolt catalog. We have imaged 31 fields of standard stars using Johnson's BVRI filters during three nights in August 2019. We have measured both extinction and color correction. Relating our calibrated magnitudes to the magnitudes of standard stars from the Landolt catalog, we have achieved accuracy of 2%-5% for the BVRI magnitudes.

scholarly journals Digitization and astrometric calibration of Carte du Ciel photographic plates with Gaia DR1

2018 ◽  
Vol 616 ◽  
pp. A185
Author(s):  
K. Lehtinen ◽  
T. Prusti ◽  
J. de Bruijne ◽  
U. Lammers ◽  
C. F. Manara ◽  
...  
Keyword(s):  
Twentieth Century ◽  
Quality Control ◽  
Large Fraction ◽  
Central Area ◽  
Digital Camera ◽  
International Project ◽  
Single Exposure ◽  
Photometric Calibration ◽  
Data Release ◽  
One Year

Context. Carte du Ciel was a global international project at the end of the nineteenth and beginning of the twentieth century to map the sky to about magnitude 14 on photographic plates. The full project was never observationally completed and a large fraction of the observations made remain unanalyzed. Aims. We want to study whether the astrometric and photometric accuracies obtained for the Carte du Ciel plates digitized with a commercial digital camera are high enough for scientific exploitation of the plates. Methods. We use a digital camera Canon EOS 5Ds, with a 100 mm macrolens for digitizing. We analyze six single-exposure plates and four triple-exposure plates from the Helsinki zone of Carte du Ciel (+39∘ ≤ δ ≤ +47∘). Each plate is digitized using four images, with a significant central area being covered twice for quality control purposes. The astrometric calibration of the digitized images is done with the data from the Tycho-Gaia Astrometric Solution (Gaia TGAS) of the first Gaia data release (Gaia DR1), Tycho-2, Hot Stuff for One Year (HSOY), USNO CCD Astrograph Catalog (UCAC5), and PMA catalogs. Results. The best astrometric accuracy is obtained with the UCAC5 reference stars. The astrometric accuracy for single-exposure plates is σ(α cos(δ)) = 0.16″ and σ(δ)=0.15″, expressed as a Gaussian deviation of the astrometric residuals. For triple-exposure plates the astrometric accuracy is σ(α cos(δ)) = 0.12″ and σ(δ)=0.13″. The 1 − σ uncertainty of photometric calibration is about 0.28 mag and 0.24 mag for single- and triple-exposure plates, respectively. We detect the photographic adjacency (Kostinsky) effect in the triple-exposure plates. Conclusions. We show that accuracies at least of the level of scanning machines can be achieved with a digital camera, without any corrections for possible distortions caused by our instrumental setup. This method can be used to rapidly and inexpensively digitize and calibrate old photographic plates enabling their scientific exploitation.

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