The Chandra Observation Visualizer

ObsVis is a tool to aid in observation planning which allows the inspection of sky images with overlaid instrument fields-of-view (FoV). ObsVis interfaces with the SAOimage DS9 image display tool, and facilitates detailed manipulation of Chandra pointing and instrument parameters.

Download ObsVis for Cycle 11 (released on 15 January 2009)

Here we provide just one very simple example of ObsVis usage for ObsVis in CIAO 4.1. If you need more detailed help using ObsVis, see the help file.

Say you want to image M33 with Chandra. It's a good idea to see when it is visible by Chandra before choosing an appropriate roll angle for your visualization of the field of view. Go to the CXC PRoVis page. If you will be happy using cataloged coordinates, type in "M33" (without quotes) to the Resolve Name box and click the Resolve Name button. After the coordinates appear, click the Generate Plot and/or View Plot Data buttons. The plot shows the Chandra roll/pitch/visibility of M33. Since it is best to avoid time-constrained observations, a likely roll angle for M33 (covering a large fraction of the year) is 120 degrees.

Once you have downloaded and installed ObsVis, start it up by typing obsvis. SAOImage DS9 should come up, as well as the ObsVis GUI.

Say your primary interest is to image the M33 nucleus with ACIS-S3, and a few other CCDs can be turned on for archival use. On the ObsVis GUI, click on ACIS-S under Instrument. Toggle off S0, S1, S4, S5. in the ACIS Chips region of the GUI. Toggle on I2, I3. Type 120 in the Roll box. Type "M33" (without quotes) into the Target Name box of the ObsVis GUI. Press the New FoV button. A new Field of View (FoV) labeled (by default) "fov0" will appear in the FoV Table section of the GUI, as shown in the GUI capture below.

After requesting a New FoV, a SAO-DSS Server box will come up with the coordinates, and a DSS image will be automatically retrieved and displayed in DS9. (If you instead wish to display a FITS image of your own, use the ObsVis GUI Adjust-FoV pulldown, toggle off Image-Auto-Reload and open your image in DS9.) The coordinates cataloged for M33 are at the aimpoint. A red marker there displays the size of the default Chandra dither pattern.

Now that you have the image and correct instrument parameters, you can adjust the DS9 display for a nice proposal image. You decide for aesthetic reasons to also remove the CCD chip labels from the display. On the ObsVis GUI, click Edit/Preferences . Select FoV Defaults and toggle off Display Chips Labels . The image below shows the result using DS9's HSV color option. To use this image for a proposal, you could in DS9 select File/Print. Use Print to File and choose Level 1 under the Postscript heading for best results with latex and PDF generation.