... The SDSS 2.5-m primary mirror is supported in a manner similar to the Apache Point Observatory 3.5-m telescope primary. ... The axial support is provided by 48 air pistons. The pistons have the same diameter thereby applying equal forces with the same air pressure. ... Each group supports a 120њ sector of the mirror. ... Figure 1: CAD drawing showing the 2.5-m primary mirror and the locations of actuators (green circles) These actuators apply forces (10*cos2 N) to correct astigmatism. ...

For non-spherical isotropic particles, the classic variant of the RDG approximation does not include the anisotropy of the shape and hence does not give the correct Rayleigh limit, say, for small ellipsoids. ... We call this variant a modified RDG approximation (MRDG). ... First, the MRDG leads to the correct Rayleigh limit. ... The second approach to generalization of the RDG is connected with the use of the Born iterations for the scattering integral equation [ 95 , 124 , 132 , 264 ]. ...

... Step 1: The magnetic field line tracing from the satellite position up to magnetic equatorial plane using IGRF magnetic field model. Step 2: Tracing back from the point (produced on the Step 1) to the Ionosphere (by using only dipole magnetic field) . ... The magnetic field line tracing from the satellite position up to the Ionosphere (the stop trace altitude 110 km) using Main (dipole) + Extraterrestrial magnetic field model (for example, Tsyganenko [1987], or [1989], or [1990] ) . ...

... These values are functions of the geographical (geodesic) latitude and the height of the point above the sea level. ... The option also permits to solve the reverse problem — to calculate approximate values of observatory latitude and its height above the sea level depending on the introduced values of dxy and dz. ... It should be mentioned that low precision of dxy and dz for some observatories in the list maintained by MPC leads to negative value of height above the sea level for some of them. ...

... Step 1: The Footprint position calculation by the magnetic field line tracing from the satellite position up to the Ionosphere by using IGRF + Tsyganenko [1987] magnetic field model (the stop trace altitude 110 km). Step 2: Tracing back from the Footprint (produced on the Step 1) to the dipole equatorial plane (by using only IGRF magnetic field model up to the geocentric distance 8 RE and dipole field model after this distance). ... Back to the description . ...

... The Galactic Center in Infrared . 8.07.2001 . ... In visible light, much of the Galactic Center is obscured by opaque dust. ... Outward bound, this primordial piece of the solar system is still just visible to the unaided eye and can now be sighted by northern hemisphere skygazers as it moves through the constellation Pisces. ... Hydrogen, Helium, and the Stars of M10 . ... Stars like the Sun use hydrogen for fuel, "burning" hydrogen into helium at their cores through nuclear fusion. ...

Subject: Use of sig_p bit. ... alt_sig_p1: MOVE ISTAT and 0x08 to SFBR ; test the connected bit JUMP alt_sig_p2, if 0x08 ; either the chip got selected, reselected, and the sig_p bit may or may not have been set MOVE ISTAT and 0x20 to SFBR ; test the sig_p bit , if here safe to assume sig_p was set and not connected JUMP sig_p_ set , if 0x20 ; big error if here -- not connected and sig_p was not set ... sig_p_set: ; system processor has set the sig_p bit. ...

PHOTOMETRIC SEARCH FOR BLACK HOLES IN DORMANT X-RAY TRANSIENTS ґ ґ Aleksander Sadowski1 , Janusz Ziolkowski2 , and Krzysztof Belczynski3 ё Astronomical Observatory of Warsaw University, Al. ... Such definition means that our statistics for the number of expected BH X-ray binaries include both transient and persistent systems. ... If this value is 2 M , then, according to our calculations, Galaxy contains some 15 000 to 40 000 of BH X-ray binaries (and some 30 000 to 250 000 of NS X-ray binaries). ...

... This will be done by fitting period-luminosity relations in the form V = a в log P + b to Cepheid variables in these two galaxies. ... 8 Marks 2. ... 3R x3 2 Marks (b) Use this expression for the pressure to show that when 1 is constant, the adiabatic wave equation for the star can be written as x d d 3 R3 2 3 [(x - x4 ) ] + [ x - (31 - 4)] = 0. dx dx 1 GM 2 Marks (c) Show that near x = 0, the solution to this equation is of the form = Ax , where A is a constant and 2 = 3 (31 - 4). ...

My colleagues and I have recently completed a series of observations of SN1999an. ... The telescope is located at Martin Observatory in Blacksburg, VA, and is operated by the Physics Department of Virginia Tech. Our IAU Minor Planet Center Observatory Code is 841. ... Attached you will find a copy of one of our images (in .jpg format) with the supernova indicated. ... Virginia Tech Department of Physics . Back to Bright Supernovae . Back to Supernova 1999an . ...

... Searching for Far Out and Wandering Worlds . ... The Real Reality Show: Would aliens be anything like us? ... The SETI Institute is after alien signals. Assuming another world is beaming a 1-million-watt radio signal in our direction, how far away can that source be before the signal is lost in intergalactic noise? ... Get instant access to subscriber content on Astronomy.com! ... If you are already registered on Astronomy.com, please log in below. ...

... 365­368, ISSN 1055-6796, Photo copying p ermitted by license only, c Cambridge Scientific Publishers Distance scale calibration from kinematic analysis of an ensemble of the galactic planetary nebulae V.V. Akimkin1, I.I. Nikiforov2, A.F. Kholtygin 1 2 2 Astronomical Institute of the Russian Academy of Sciences, Russia Sobolev Astronomical Institute of St. Petersburg State University, Russia Received 1 February, 2012 We study the kinematics of ensembles of planetary ...

. N OTE: . Only clusters with R<60 kpc were used to compute the spatial parameters and metallicity gradients for all subsystems except the corona. The numbers in parantheses give the number of clusters for which the corresponding parameter is known. The X O scale length of the old halo is strongly distorted by the observed asymmetry of the distribution of the corresponding clusters projected onto the XY plane ( Fig. 4А ) . discussion in the text | previous table .

Irregular phenomena in the Earth Pole oscillation process and temporal variations of geopotential Valery Bondarenko, Vadim Perepelkin s The observed irregular phenomena in the Earth Pole oscillation process are very variety. ... These phenomena indicated in the IERS data are the "abnormal" fluctuation of the Earth Pole coordinates which owing to changing of the geodynamical parameters gives negative result in interpolation and forecast of the first approximation mathematical model. ... Fig. ...

... Possible methods for receiving ultra wideband chaotic signals are considered in the case of multipath indoor propagation (line-of-sight channel model). ... Assuming that sampling time is s=1/(2f) we obtain the data rate ~ 110Mbps.So for transition of a bit we need the information interval ~ 9ns. ... The through the background (circles)- (a); result of propagation of chaotic radio pulse indoor channel (the upper curve) and the total of the previous five information intervals SNR performance - (b). ...

... In this case you have to write in your answer (in English or Russian): «impossible situation ­ ». ... The name of the moon in the solution and in the drawings should be written (or duplicated) in English. ... The answers "which moon" and "in what case" (configurations at the moment of Jupiter disappearance) have to be given in the form of drawings, and calculations should be the base for the answers. The names of the moons in the solution and in the drawings should be written in English. ...

... Bad Astronomy . ... News . ... In the following article, I used the wrong number to get the circumference of the Earth at the latitude of Cape Canaveral, which ironically is what I accuse Ms. vos Savant of as well! ... At the Equator, the Earth spins at 1000 miles per hour (the Earth is 24,000 miles around, and spins once every 24 hours). ... The math is a wee bit hairy, but not too bad, to calculate the circumference of the Earth at Cape Canaveral assuming the Earth is an ellipse with these numbers...

IBIS Data Analysis . ... IBIS . ... Flat Fielding - Introduction . The images obtained by IBIS will have intensity variations across the field of view that are not due to the solar image, but rather caused by instrumental effects that alter the observed intensity in each point of the field of view. ... IBIS Flat Fielding Techniques . ... Therefore, it is desirable to obtain the flat field measurements center on a point along the equator near the heliographic center of the solar disk. ...

Magnetic Stars, 2011, pp. 153 ­ 156 Ab out the Dep endence of the Rotation Velo city of CP Stars on the Magnetic Field Glagolevskij Yu. ... Based on the observational data of the average magnitudes of the surface magnetic field strength Bs for a number of chemically peculiar stars we investigate the dependence of the rotation period on the magnetic field. ... Now the periods of rotation P and the average values of the surface magnetic field Bs are known for more than 50 magnetic stars. ...

... 2001 July 7 . A Close Encounter Of The Stellar Kind . Credit: Digitized Sky Survey , SkyView . Explanation: The unassuming star centered in this sky view will one day be our next door stellar neighbor. ... This future stellar encounter was discovered by researchers Joan Garcia-Sanchez and Robert Preston ( JPL ), and collaborators while studying stars in the solar neighborhood using data from the Hipparcos Astrometry Satellite . ... About APOD | ...