... When creating a mosaic from a set of individual frames, the correct background offset for each frame must be determined for proper matching. In this paper we describe a method for constructing a mosaic from a set of individual frames by applying a minimization technique. ... Typically these are frames with some known defect (see ? ... Determining which frames to exclude from the final mosaic is critical, since one bad frame can create background offset errors that propagate throughout the mosaic. ...

... Status of the numerical solutions and validation 2. ... Coupling of "solid" Earth components, e.g. core ­ mantle (Dehant et al.) ... Consistent relativistic formulation of Earth rotation (Gerlach, Klioner, Soffel) Status of the numerical solutions - 2 · The results from numerical solutions suffer from ­ Simplified solid Earth models ­ Incomplete Earth system models or neglecting of certain parts or neglecting of certain coupling mechanisms ­ Methodological limitations of computations...

... Three different techniques for averaging have been introduced. ... The average functions mentioned above will normally produce a result frame whose world coordinates are the intersection of the father frames' world coordinates. ... Averaging statistically consistent values --- љ This command differs somewhat from the purely mathematical functions of the previous two commands in the sense that it tries to anticipate some of the astronomical content of the input data frames. ...

Atmospheric influence on the different radio-engineering system functioning . ESTIMATION OF ATMOSPHERIC OPTICAL CHARACTERISTICS AND REMOTELY SANSED IMAGE CORRECTION . ... Direct transmittance estimation results for 12 channels of the spectrometer CHRIS. ... We have managed to develop a direct method of estimating the discrete Normalized Atmospheric Point Spread Function (NAPSF) from available images alone, not using any external sources of information about the atmosphere. ... IRE RAS 1996-20 11 ...

Scale-heights of the Galactic disk subsytems with different ages and metallicities . V.Marsakov & Yu. ... It is based on the fact, that all stars cross the disk plane several times during their Galactic orbital period. ... We have used our representative sample of nearby disk F2-G2 stars Marsakov & Shevelev (1995) in which fundamental stellar parameters was determined on the basis of published date on uvby-photometry, proper motion and radial velocities. ... Marsakov V.A., Shevelev Yu.G. Bull. ...

Next: The Scenario Machine: Operational Up: Evolution of Magnetic Rotators Previous: Ejector-propeller hysteresis . ... The length of this segment is determined by the eccentricity. ... In this case no hysteresis occurs and transitions E -- P and the reverse take place in symmetrical points of the orbit. ... Here EP means a mixed state of the rotator at which it is in the ejector state during one part of the orbit, and in the propeller state during the rest of the orbital cycle. ...

... The polygons of different observatory . ... geographical (Greenwich geocentric) . coordinates of the polygon's corners, . or by the geographical coordinates . ... GGLat (deg) . GGLong (deg) . ... Polygon's corners . geographical coordinates . Back to the top . Polygon's corners geographical coordinates . ... The central point geographical . coordinates and extensions . ... GGLat extension (deg) . ... GGLong extension (deg) . ...

Next: What We Will Up: Improved Prescription Retrieval and Previous: Prescription-Based Optical Modeling . ... Prescription retrieval provides a means of improving estimates of prescription parameters by computer processing of image data (Fig. ... Prescription retrieval takes as a starting point the . ... The prescription retrieval process takes image data as input. ... The best results are obtained using several images simultaneously, preferably images that use different field and focus points. ...

... In the pn-CCD, 768 individual amplifiers allow fast readout, but imply different gains for the different readout channels which all have to be determined and corrected for. The gains of the 768 readout nodes were derived by comparing the position of CTI corrected calibration lines (in adu) with their known energy. ... More details on the CTI and gain correction can be found in []. ...

Detection technique . We are using ISIS , the optimal image subtraction method developed by C. Alard & R.H. Lupton, to search for SNe in our images. ... The second image shows the same subtraction, but after the convolution of the best image with ISIS: . ... For this reason, we are suggested to search for nuclear SNe with NICMOS on HST, to exploit its stable PSF, sensitivity and angular resolution to detect from space nuclear obscured SNe which might have been missed by ground-based surveys. ...

Next: Imaging Polarimetry with NICMOS Up: NICMOS Data Calibration and Previous: The Photometric Performance of . ... NICMOSlook and Calnic C . ... Extracting spectra from a large number of NICMOS grism images requires a convenient interactive tool which allows a user to manipulate direct/grism image pairs. ... NICMOSlook and Calnic-C are two programs that were designed to take advantage of the fact that the NICMOS grism mode typically consists of taking both a direct and a grism image. ...

Quasar VLBI network observatories as co-location sites A. Ipatov, I. Gayazov, S. Smolentsev Institute of Applied Astronomy, Saint Petersburg, Russia ... supposes: 1. installation of different observational techniques at sites (co-location) 2. combined processing of different types of observations (collocation) IAA activity in space geodesy · Quasar VLBI network : ­ VLBI observations ­ GPS /GLONASS observations ­ DORIS ( ...

... The user provides SCHED with source coordinates in one of the J2000, B1950, or DATE coordinate systems. ... This date is specified using PRECDATE . ... This is enough to harm phasing of the VLA at high frequencies and enough to be rather undesirable for positions used on the correlator. ... For example, the B1950 coordinates of the VLA calibrators are either based on absolute measurements made in 1979.9, or are converted from more modern J2000 coordinates using an assumed ``observe'' date of 1979.9....

... Each data set has 36 values in it. ... If it is, what can you conclude about the nature of the data? ... Data Set 1: 12.8 8.4 12.5 2.5 1.1 0.4 1.4 0.4 0.1 1.6 6.4 9.3 6.9 6.8 7.6 2.9 2.2 0.9 1.2 2.1 0.1 5.7 8.5 7.1 9.8 7.6 6.2 1.9 0.9 0.2 0.4 2.0 1.1 1.9 1.3 1.2 Data Set 2: 6.8 12.3 10.6 3.4 1.8 1.8 1.8 3.2 0.5 1.4 13.1 7.5 2.1 9.6 6.4 5.4 3.9 3.9 0.3 0.1 0.9 6.1 18.7 4.6 0.3 5.1 5.7 0.5 1.5 2.5 1.4 0.1 2.1 4.8 6.3 3.5 Data Set 3: 6.9 2.6 8.6 7.9 6.9 3.7 1.1 1.8...

ALMA | ... In this section, we explain why we need to correct phase fluctuations and ALMA's strategy to do this. Rapid fluctuations will be corrected with water vapour radiometers (WVRs). The Cavendish Astrophysics Group was also a leading contributor to the ALMA prototype WVRs, which were put through their paces in tests at the Submillimeter Array (SMA). ... The Cavendish Astrophysics Group in partnership with the Onsala Space Observatory built two prototype WVRs for the ALMA project. ...

Astronomy Picture of the Day . ... The different colors of this planetary nebula are determined by small differences in its composition. This bipolar nebula will continue to shine brightly for only a few thousand more years, after which its central star will fade and become a white dwarf star. ... Publications with keywords: bipolar - planetary nebula - butterfly nebula . Publications with words: bipolar - planetary nebula - butterfly nebula . ... NGC 3132: The Eight Burst Nebula . ...

... Description . Catalog . ... In the Catalog, we publish equatorial (ЮБ 2000 , ЮД 2000 ) and galactic (l,b) coordinates of cluster centers derived as the position of overdensity in 2MASS catalog (Koposov et al. ... Distances, color-excesses and ages are the mean-square values calculated using all available evaluations from different color-magnitude diagrams. ... There are individual pages for every cluster where all available plots and parameters are published. ... 2002). ...

... Resolved Stellar Populations Globular Clusters . Galaxies are made of stars, gas and the illusive dark matter. ... Star clusters are the simplest form of the stellar population. ... Old globular clusters are easily observed at great distances and can be used as probes of the early stages of star formation history in galaxies where individual stars cannot be resolved. My research interests are centered on the studies of resolved stellar populations and (old) star clusters in nearby galaxies. ...

The ESA/ESO Astronomy Exercise Series 2 . The Distance to Messier 100 as Determined by Cepheid Variable Stars . ... The small variations in distance to the individual Cepheid variable stars in the Cloud are negligible compared with the much larger distance to the SMC. ... In this way Cepheid variable stars can be used as one of the 'standard candles' in the Universe that act either as distance indicators themselves or can be used to calibrate (or set the zero point for) other distance indicators. ...

... Thomson's multiple window method of spectral estimationthomson provides a very good estimate of the power spectrum by measuring the energy contained within a collection of rectangular shaped frequency intervals. ... Often, much of the fine structure of a spectral estimate is due to noise. It should be stressed that while other methods of spectral estimation (such as the Welchoppenheim method) exist, the Thomson method is particularly noteworthy for its precisely defined rectangular frequency bins. ...