... Q: How do I best determine an observation's actual orientation? ... The science header keyword ORIENTAT is populated by adding the angle between the HST V3 axis and the detector Y axis to what we will call the "commanded roll" (North to V3 through East). ... The commanded roll can be determined by subtracting the beta_2 from ORIENTAT. ... Relying on the jitter file's measured roll if a problem is found either with the science header population or with the execution of the commanded roll. ...

Next: Discussion Up: The Second EGRET Catalog Previous: First Catalog Sources . In the first EGRET catalog, upper limits were given for selected objects not detected during the Phase 1 all-sky survey. These upper limits are determined using the likelihood calculation and depend on the EGRET exposure to a given direction, the contribution of the diffuse gamma radiation, and the proximity and strength of detected sources. ...

... Tonight's Sky . ... The Magazine . ... Observing . ... Star Atlas . ... stars . ... The double star 54 Leonis, spiral galaxy NGC 3198, and emission nebula NGC 3199 . ... Astronomy for Kids . ... Observing springtime deep-sky objects with a large telescope . ... How do astronomers determine the ages of stars? ... Get instant access to subscriber content on Astronomy.com! ... Receive news, sky-event information, observing tips, and more from Astronomy's weekly email newsletter. ... Astronomy Magazine ...

... In this poster we propose a hypothesis that within fixed assumptions about internal physics (opacity, thermodynamics, nuclear reactions) a strict relation between the surface helium abundance and the entropy of the adiabatic part of the convective zone exists for all solar models. This hypothesis is verified with models under simplified physics (Christensen­Dalsgaard 1988) and with six evolutionary models computed by Christensen­Dalsgaard (1992). ... 1990, Christensen­Dalsgaard 1991). ...

... Meta Index / Home Page / Description / Specifying source region shapes . When radiusstyle =`contour', the task calculates the source region shape as an elliptical locus which approximates the contour of the PSF at a given flux value. ... Clearly, in order to calculate the shape of such a flux contour, it is necessary firstly to normalize the PSF to the source brightness and secondly to determine the flux level (in `brightness' units per pixel) at which to find the contour. ...

... Optical constants of amorpous SiO 2 and GeO 2 in the region of valence band. ... The optical constants were determined by 4 methods: (i) Measurements of reflectivity of polarized radiation incident at 3 different angles following by solution of the Fresnel equations; (ii) Measurements of trasmittance (for tablettes of ultra-fine powder); (iii) A combined method applied to both kind of the data following by solution of Fresnel equation for the normal incidence; (iv) Kramers-Kronig method. ...

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... Armagh Observatory, College Hill, Armagh BT61 9DG, +44 (0)28 3752 2928 . ... We discuss the diagnostic potential of high cadence ultraviolet spectral data when transient ionization is considered. ... The ionization fraction of the transition region ion O v and in particular the contribution function for the O v 1371 line are computed within the Atomic Data and Analysis Structure, which is a collection of fundamental and derived atomic data and codes which manipulate them. ...

... We cannot use for this purpose equivalent widths and profiles of HI lines (well known criteria of atmospheric conditions for normal supergiants), since these lines are strongly distorted in the spectrum of IRAS04296 as seen in Fig. ... Figure: Upper: iron abundance FeI (circles) and FeII (crosses) calculated for IRAS04296+3429 with model parameters , and using lines with different excitation potentials EP of a low level; bottom: the same as a function of the equivalent width W . ...

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. ...

The local time is a time determined for the given place on the Earth; it depends on the geographical longitude of the place and is the same for all points on the meridian. ... For each place of Russia being on the longitude l it is possible to indicate the true local solar time Ti; the local medium solar time MT ; the local zone time Tp; the winter season time Tw ; the summer season time Ts; the local star time S. Here are the formulas for those who need to transform one time into another: . ...

Short Notes phys. stat. sol. (a) K2 1 K21 (1975) 27, Subject classification: 18.2: 21.1; 21.1.1 Solid State Physics Institute, Academy of Sciences of the USSR, Chernogolovka The Effect of Pressure on the Curie Points of Fe-Ni-Cu and Fe-Ni-Mn Alloys BY V.E. ANTONOV, G.T. DUBOVKA, and E.G. PONYATOVSKII There is a series of papers on the effect of pressure on the Curie points T of C Fe alloys with other transition elements. ... The dependence of the Curie points on pressure is linear. ... 1 Fig. ...

Next: Antenna gain considerations and Up: Some Theory Previous: Polarisation . To provide correct flux density units for the visibilities, , from an interferometer, the measured correlation coefficient at the correlator ( ) needs to be scaled by a system temperature and a telescope sensitivity factor ( ). ... For a zenith opacity , observing at an elevation of , and if the atmosphere is approximated as having a uniform temperature , then the atmospheric contribution to system temperature is . ...

... The file names' construction . The flight (m) stage's file set . ... the orbital data used for the flight operation monthly (m) long-term planning, . ... The orbital calculations are based on the initial orbital data determined by KIAM RAN using the orbital radio- measurement treatment. The determined initial orbital data are presented as a state vector (satellite position and velocity) in the J2000 reference. ... Accept the file with extension '.bgr', where the Moscow time (MT=UT+3h) is used. ...

THE PHOTOMETRIC RESEARCHS OF THE MERCURY'S SURFACE BY MEANS OF DIGITAL MODELS. ... The surface brightness of Mercury was measured Danjon (1933, 1949, 1953) and Harris (1961) in phase angle 3o-123o. The analysis of the various data of the integral photometric gives the results of determination of the main photometric constants for Mercury. ... THE PHOTOMETRIC RESEARCHS OF THE MERCURY'S SURFACE: S.G. Pugacheva The surface brightness of the Mercurian images was established on the geologic map Mercury. ...

Triad, launched September 2, 1972, was an experimental spacecraft designed to move in an accurately predictable low-altitude orbit, allowing its position to be used as a reference point in navigation. ... While the "proof mass" thus moved in an accurately predictable orbit, the spacecraft itself was subject to air resistance and sunlight pressure, causing it to move slightly differently. ... Exploration" home page (index) Glossary . Official GSFC Home Page .. NASA WWW Home Page . ...

Federal Communications Commission (ix)(A) For a station authorized pursuant to § 73.215 or Sec. § 73.509, a showing that the root mean square (RMS) of the measured composite antenna pattern (encompassing both the horizontally and vertically polarized radiation components (in relative field)) is at least 85 percent of the RMS of the authorized composite directional antenna pattern (in relative field). ...

... Ser. 27, 21 # by adding a constant offset in m_AB. The offset is determined for the region # 5250-9200 Angstroms. Not recommended shordward of 4250 Angstroms. There are strong features in # the region 3750-4250 Angstroms , and there is an offset of Oke from the # model shortward of 3750 Angstroms , where m_AB varies very rapidly with # wavelength # SET .Z.UNITS = AB magnitudes SET .Z.LABEL = Flux SET .Z.REVSCALE = 1 SET .Z.MAGFLAG = 1 SET .TABLE.BANDWIDTH = 50 ...

... 172 ] Briefly, the count rate at the detector from a source at a redshift z is . ... Figure 55 shows the ``Green functions'' for the double compact binary merging rate   evolution assuming no collapse anisotropy. ... Another way that diverse peculiarities in the - distribution induced by the sources evolution could arise is connected with a possible non-monotonic character of the star formation rate in galaxies. ... 22 ] Figure  56 shows two-dimensional cuts through the parameter space. ...

... Bad Astronomy . ... Mad Science . ... Universe Today . ... Keep Bad Astronomy close to your heart, and help make me filthy rich. ... type 1a supernovae seem most useful . ... This is a bright, massive star that explodes after fusing all the light elements in its core. ... That means we can calculate how far away it is. ... This is exactly what we are trying to do with these supernovae; look far enough away that any deviations from flatness of the Universe can be seen. ... Phil Plait . ...