... Stellar Evolution is driven entirely by the never ending battle between Pressure and Gravity . As imbalances are reached, the star is driven to find a new Energy source. ... Pressure and gravitational forces are equal, the star is stable and its core is sufficiently hot to fuse Hydrogen into Helium More about main sequence stars . ... The luminosity generated by the core fusion of Helium into Carbon is far greater than the shell luminosity associated with the fusion of Hydrogen into Helium. ...

... Telescopes . ... CCD photometer . ... One of the principal devices used in observations at the telescope Zeiss-1000 is a CCD photometer. ... The count rates (electron per second) for ADU = 1e - computed throughout the image for U = B = R = I = 20.0 for an object observed at air mass equal to 1.0 with the given version of CCD at the telescope Zeiss-1000 are presented in Table 1. Table 1: Quantum efficiency and count rate in the broad-band system of the CCD photometer of the telescope Zeiss-1000. ...

... Standard magnitudes can only be computed for the U, B and V filters and hence the only standard colours that can be calculated are U-B, B-V and U-V. An important point to note, is that these standard colours can be computed using the following instrumental colours - U-B, B-V, U-V, (UVW1-U), (UVW1-B), (UVW1-V), (UVW2-B) and (UVW2-V). ... The program loops through these colours and if the relevant instrumental magnitudes are present computes the standard magnitudes and standard colour. ...

The Agile window provides complete control over the Agile high-speed photometer. ... All other parameters are specified as part of the command that starts an exposure sequence. ... To connect the filter wheel controller, issue this command in the command bar at the bottom of the Log window: agile connDev fw . ... To home the filter wheel controller, issue this command in the command bar at the bottom of the Log window: agile fwhome (there must be a filter wheel mounted in Agile for homing to succeed). ...

An improved correlator for ALMA has been proposed by an European consortium including Astron (NL), Bordeaux University (FR), IRAM (FR) and Arcetri. ... The work in Arcetri has focused on the efficent design of a digital receiver, that exploits the peculiarities of the astronomical signal, i.e. the extremely coarse quantization and the stochastic nature of the input signal. ... A complex mixer followed by a two stage bandpass filter. ... Phase effects in a hybrid correlator . ...

... The absolute flux calibration of NICMOS will be calculated from observations of standard stars with known flux distributions F( ). ... In order to expand the set of IR standard stars in the appropriate flux range for NICMOS, M. Rieke, R. Thompson, and collaborators at the University of Arizona are making photometric observations of solar-analog stars, which will be used to normalize the solar spectrum to the observed IR magnitudes. ... Relative flux references accurate to 1.5% for standard...

... The first step to improve the FORS calibration is therefore to obtain data to allow a computation of the illumination correction across the field. ... Another limitation on the calibration accuracy has been the brightness of the Landolt standards which have forced the use of extremely short exposures introducing small but non-negligible shutter-time errors and also resulting in a very small number of useful standards per frame. ...

Next: Hierarchical Wiener filtering Up: Noise reduction from Previous: The convolution from . Let us consider a measured wavelet coefficient at the scale i . We assume that its value, at a given scale and a given position, results from a noisy process, with a Gaussian distribution with a mathematical expectation , and a standard deviation : . ... We get: . ... This is done from the study of the variation of the noise between two scales, with an hypothesis of a white gaussian noise; . ...

... Superb optical performance coupled with time proven computerized pointing and tracking has made the LX200 ACF series a best-seller in the high-performance telescope class. ... MeadeтАЩs new LX70 Series offers high-quality German equatorially mounted telescopes with slow-motion controls and heavy-duty steel tripods. ... For crisp wide-field observing and imaging, few optical designs match the performance of a true triple-element apochromatic refractor. ... Meade Standard Field Tripod #07020. ...

... I have compiled a list of throughput filter curves from a variety of telescopes, instruments, and surveys. Click on the name of the filter to download it. The first line of each filter is the zeropoint for that filter. If the filter is in the AB system, it is listed as 0.0 (or in otherwords -48.55). ... Filter . Effective Wavelength . ... A_V . ... 0.987 . ... 0.050 . ...

12feb07 Measuring the SEFD around 1100 Mhz . ... bandpass filter low frequency falloff around 1130 Mhz . ... A 500 Mhz bandpass centered on 1100 Mhz (via the spectrum analyzer) showed a 6 db difference between 1100 Mhz and the noise floor at 1000 Mhz. ... The interim correlator was used with 25 Mhz bands centered at: 1040, 1060, 1080, and 1100 Mhz. ... 1040 Mhz cfr trking src(.gif) There is probably not very much sky signal getting into this band so it looks better than it should. ...