SkyView Blog

This afternoon we released the new Jar version 2.4b of SkyView. The changes are predominantly internal and are described in a previous post. However, there is one change that affects the SkyView web site. An old feature from the pre-java version of SkyView is returning. When Catalog Overlays are selected in the Query Form a link to the source listing is currently displayed with each SkyView image. Now there is also a link to the HEASARC Browse query used to obtain the listing providing much more data about each source. Note that HEASARC Browse uses a cone search that may return more catalog sources than would appear on the SkyView image.

This afternoon we released the new Jar version 2.4 of SkyView. There have been a lot of incremental changes since our original release of 2.3. Today’s release includes new or enhanced support for 3 projections (Arc, Stg and Sfl) and has support for two new surveys that should be coming on line in the next few days. There are a number of bug fixes (e.g., see the recent post on Smoothing), and our new RefCoords setting which allows fixed projections to be centered anywhere on the sky. This capability was added in response to a user request. So please let us know if there’s something you need!

A new version of the SkyView User’s Guide and a new set of the JavaDoc’s documenting the classes has also been released.

New features and surveys should be showing up in our on-line version later this week.

SkyView treats a number of projections (Aitoff, Cartesian, Sansom-Flamsteed/Sinusoidal) as fixed projections. Regardless of the position you specify, the sky is projected to the plane in the same way. All that your coordinate entry changes is the center of the image you get. Thus if you ask for an image near the pole in a Cartesian projection, you’ll find that there’s a large distortion since you are near a singularity in the projection. By contrast, projections like the Tangent and Sine projections are centered at the position you specify: that’s the point of minimum distortion.

If you wanted to make an Aitoff or Cartesian map really centered on some point other than the coordinate origin, older versions of SkyView couldn’t help you. With the version we’re releasing today, you can specify the new RefCoords setting. It takes a pair of decimal coordinates and uses that as the coordinate center for fixed projections. E.g., use RefCoords=0.,90. Position=0.,90. projection=Ait to ask for an Aitoff projection centered around the pole. Note that you still need to specify a position.

The smoothing algorithm has a problem: It propogates NaNs to the right. A new version of SkyView with this fixed will be released on April 29.