SkyView Version 2.6

Version 2.6 of SkyView has been released. The major change is largely invisible to the users. When using the Clip sampler on large images we sometimes run into a problem where the corners of a user pixel when transformed into the survey projection, straddle a cut in the image. E.g., if the survey is an all-sky Cartesian projection, a user pixel crossing Longitude=180 may have corners to the far right and left of the survey image.

A new set of classes deals with straddles in Aitoff, Cartesian, TOAST and TEA projections. An update for the CSC projection should be available soon. Straddles are not an issue in projections like the Tangent plane (gnomonic) projection where there are no cuts in the image. The previous code could incorrectly sample data along the projection cuts.

Version 2.6 allows multiple values for the scaling keyword so that different surveys can be scaled differently. This can be especially useful for RGB imags.

A facility for allowing lower resolution images to be used when a user requests very large regions has been added to help support new optical surveys. This may be the first step in the direction of supporting hierarchical resolution images, a la, Google Sky and WWT.

The offset command used when drawing over an image has been enhanced.  By default offsets are made starting at the center of the image.  Instead of specifying two numeric values for the offset, an offset string of  “++”, “+-“, “-+”, or “–” may be given to offset to one of the corners of the image where the first character refers to the X-axis and the second to the Y-axis.  Offsets are added together so, e.g., to put draw text 100 pixels above and to the left of the lower right hand corner we could use the commands

   offset +-
   text -100 100 0 MyText

or

   offset +-
   offset -100 100
   text 0 0 0 MyText