The information displayed below web form query image results now includes the coordinates of the requested center in decimal format. This applies to queries where the entered position is in any format other than decimal (object name, coordinates in sexagesimal format, etc). We thought this additional image information might be helpful.
The LogLog scaling that was the subject of a previous post has been added to the SkyView Query Form. Look for it as a Brightness Scaling option in the Other Options section.
For years we have provided two scripts (skvbatch and webquery) that can be used together to run batch SkyView queries. Recently users have had problems using the scripts due to local firewall issues so we are providing a new script (skvbatch_wget) that uses the GNU utility wget and should work behind firewalls. For more information please visit our Batch Page.
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.
The current SkyView JAR files were compiled using Java 1.5. We’re likely to move to 1.6 in the next release unless we hear an outcry from our users. It should be a little faster but if you just download the JAR file and use it on your machine you will need to have 1.6 installed. We’ll add a link to a 1.5 version, but we’ll likely stop updating that in a release or two.
The GALEX release was accompanied by a few other changes. The one that some users may notice is that for surveys where the data is gzip compressed, SkyView should be a little faster. SkyView was sometimes reading the entire image when it only needed to read the FITS headers.
To support the GALEX survey the image finder code in SkyView was updated. In SkyView an image finder is used to find the input image that should be sampled for each pixel in the output image. A new abstract class RectRecurse encapsulates a basic underlying algorithm which says that if we can find a rectangle in the output image where all of the pixels on the edges of the rectangle should be sampled from the same input image, then we can sample the entire rectangle from that input. This class supports two new settings: MinEdge and MaxRad. The MinEdge setting specifies that input images should not be sampled less than MinEdge pixels from their edges. Similarly MaxRad specifies that they may not be sampled at a distance greater than MaxRad from their centers. Note that the units used are pixels in the input image.
The RectRecurse class is extended by non-abstract classes that define criteria for how to pick the best input image for a single pixel in the output image. Current classes include Border which returns the distance from the edge of the image. This is the default for all but the GALEX survey. ScaledBorder is similar except that it scales the pixel distance by the size of the image. It can be useful if the images in the survey are very different in size. Radius returns essentially the inverse of the distance between the output pixel and the center of the input image. MaxExposure returns the exposure of the input image. That is the default for GALEX (where a MaxRad value is also specified).
When putting these in place a change to the main SkyView class was also made so that the ImageFinder and Mosaicker can be specified in the survey specific settings.
SkyView now includes data from GALEX. This is a major new survey for us. GALEX provides high resolution images in the ultraviolet for about a quarter of the sky. This fills a substantial hole in the resolution/regime coverage for SkyView. The GALEX data are accessed through the Web from MAST. Currently the fourth release of GALEX data (GR4) is being ingested and we will update the survey description to include new data as it becomes available.
By default GALEX uses a different image finder than other surveys. When it needs to choose which input image to sample for a given output pixel, it looks only at images whose center is under some maximum radius from the position of the output pixel and then chooses the one of those with the longest exposure time. The maximum radius is currently set to 0.58 degrees. These settings can be overridden if you use the SkyView-in-a-Jar locally, but are fixed for the Web interface.
A three color image of M81 with Red=DSS2R, Green=GALEX Near, Blue=GALEX Far
A new survey including seven bands of data from the ROSAT All Sky Survey data has been added to SkyView. The RASS Background 1-7 data show the entire sky in diffuse X-ray emission. Point sources have been subtracted out. This new survey replaces the RASS 1/4, RASS 3/4 and RASS 1.5 KeV maps. Those data are still available but we no longer display the survey names on the Web page. You can still access them through the batch interfaces or using the Jar file. The new data sets have better spatial and energy resolution and were built by the Steve Snowden who also created the earlier maps.
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.