Finding images using IRSA tools

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Finder Chart and IRSA Viewer are two tools at IRSA. Both use software that is called "Firefly", and as a result, both tools have a similar look-and-feel. Finder Chart was originally designed to create finder charts for use at a telescope, but it has evolved into one of IRSA's most popular tools. It provides images from up to 5 surveys in up to 21 bands, and allows simultaneous searches of the corresponding catalogs. IRSA Viewer is a more generic version of Finder Chart, providing the FITS viewer and one-by-one image retrieval and catalog searches.

In both cases, the search capability is integrated with the FITS viewer capability. (In Skyview, these capabilities are not integrated.) When Finder Chart or IRSA Viewer give you images as a result of a search, you are looking at (and interacting with) the original FITS files. There is a toolbox on the top of both tools that can be used with the images. You can change color stretches and color tables, you can leave markers on the image, you can read in catalogs (and ds9 regions files), etc. In Finder Chart, by default, all the images are locked together, so what you do to one image (zoom, etc.), happens to all of them. (To unlock them, click on the lock icon in the image toolbox.) (Just for completeness, in IRSA Viewer, there is no a priori guarantee that the images that are loaded are of the same patch of sky, so they are by default NOT locked.)

You can also measure distances in Finder Chart (or IRSA Viewer), which is a very common need. Click on the ruler icon, then click and drag in the image to measure a distance. Click on the layers icon to bring up a pop-up that specifies the units for the length of the vector you have drawn in degrees, arcminutes, or arcseconds.

Images retrieved via Finder Chart or IRSA Viewer are coming from the original archives corresponding to each survey, so they are basically guaranteed to be unresampled images, so they are OK for doing detailed science, including photometry. There is an excruciatingly simple way of guesstimating photometry within Finder Chart or IRSA Viewer, but it's nowhere near accurate enough for scientific analysis.

Finder Chart and IRSA Viewer also let you retrieve and overlay catalogs. Skyview doesn't let you do that at all. On the other hand, Finder Chart and IRSA Viewer are limited to the tiles currently publicly stored here at IRSA; most of the time, you won't notice the tiles, but the 2MASS tiles are crazy small (that's a technical term) so if you ask for any reasonable amount of sky at all, you'll get a tiny 2MASS image surrounded by black, blank sky. In order to get big 2MASS images, you should use IRSA Viewer to access the 2MASS 6-degree (not 6x deeper but 6d) images, which are larger tiles, so you are less likely to find an edge.

Click on "prepare download" to get the FITS (or the pngs, or a pdf, or the html for that matter).

The IRSA YouTube Feed has playlists collecting videos on both Finder Chart and IRSA Viewer.