... Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer. 2001 May 10 . Spirals On Edge . ... When seen edge-on, their appearance is very different but no less striking as their central regions bulge and dark cosmic dust lanes appear silhouetted against starlight from flattened galactic disks. ... About APOD | ...

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. ...

... This script also shows a simple but crude way of displaying more feedback while operating: it opens the DIS Expose window. ... As always, get permission to use DIS before commanding it. import TUI.TUIModel def init(sr): """Open the DIS Expose window so the user can see what's going on.""" tuiModel = TUI.TUIModel.getModel() tuiModel.tlSet.makeVisible("None.DIS Expose") def run(sr): """Sample script to take a series of DIS calibration images and demonstrate looping through data in Python. ...

... A detector map is used to provide a grid of positions over which to calculate and flux weight the ARF. The default detector map is 'flat' which has a weighting of 1.0 for each detector map pixel and is rectangular having sides which just encompass the region specified in the DSS. Only detector map pixels falling within the source region are included in the ARF calculation, e.g. for a circular source box, the pixels in the corners of the detector map will be ignored. ... flat : . ...

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. ...

Pyramid Ice Crystal Halos Over Finland . ... This actually happens when a nearly transparent sheet of pyramid shaped ice crystals falls from the sky in a common orientation. ... An amazing display of pyramid ice crystal halos was captured on June 5 above Tampere , Finland . Visible above are very usual sun halos of 9, 18, 20, and 23, and 24 degrees. In contrast, thin and flat falling ice crystals will produce a halo of 22 degrees only. ... NASA Web Site Statements, Warnings, and Disclaimers . ...

... Wavelet analysis works most convincingly on complicated data sets. ... These wavelet maps promptly represent an overwhelming amount of information, that must be reduced in order to be useful. The reduction can take two basic different forms, and countless variants. In the sift-and-discard approach, features of interest are enhanced and the rest is removed from the wavelet maps: applications such as denoising or event identification are representative. ... Mon Nov 13 10:51:25 EST 1995 ...