Finder Chart: Overview

Finder Chart is a searching and visualization tool that allows cross-comparison of images from various surveys of different wavelengths and different epochs. Data can be downloaded in any of a variety of formats, either singly or in bulk. Catalogs from any of a variety of sources are also available.

This tool provids access to data sets from the Two Micron All Sky Survey (2MASS), the Wide-field Infrared Explorer (WISE) AllWISE all-sky survey, the InfraRed Astronomy Satellite (IRAS) all-sky survey, the Digitized Sky Surveys (DSS) (both First and Second Generation), and the Sloan Digital Sky Survey (SDSS).

This version of Finder Chart (which resembles many other recent IRSA tools) will ultimately entirely replace the prior version of Finder Chart. The old version of Finder Chart (with the old look-and-feel) is still available (here), but will be entirely removed in the near future.

Note that there are also Finder Chart video tutorials, available at the IRSA YouTube channel. Look for the playlist collecting all the Finder Chart videos in one place.

Please note that the DSS and SDSS data do not reside at IRSA, so the successful retrieval of DSS and SDSS data depends on the operation of the DSS and SDSS services, located at other institutions.

This service makes use of components of Montage, funded by the National Aeronautics and Space Administration's Earth Science Technology Office, Computational Technologies Project, under Cooperative Agreement Number NCC5-626 between NASA and the California Institute of Technology.

Contents of page/chapter:
+Surveys, Wavelengths, and Sky Coverage
+Searching and Results
+Visualization
+Downloading Data
+User Login

 

Surveys, Wavelengths, and Sky Coverage

DSS

The Digitized Sky Survey (DSS) is a digitization of the photographic sky survey plates from the Palomar and UK Schmidt telescopes. DSS images have one-arcsecond pixels and use three broad-band filters covering roughly 3950 Angstroms to 9000 Angstroms. None of the underlying datasets are all-sky; the DSS "surveys" are actually composites of multiple image sets taken at different times using different instruments. For more detailed information on filters, dates, and coverage, see the DSS webpage at STScI.

imagebandapprox. wavelength range
DSS1BBj3950 - 5400 Angstroms
DSS1RR6125 - 6475 Angstroms
DSS2BBj3950 - 5400 Angstroms
DSS2RR6300 - 6900 Angstroms
DSS2IRI6950 - 9000 Angstroms

SDSS

The Sloan Digital Sky Survey (SDSS) is not an all-sky survey, but covers more than a quarter of the sky in five optical filters, at about 0.5 arcsecond resolution. For more detailed information on filters, dates, and coverage, see the SDSS webpage.

BandApproximate central wavelength
u2910 Angstroms
g4810 Angstroms
r6230 Angstroms
i7640 Angstroms
z9060 Angstroms

2MASS

The Two-Micron All-Sky Survey (2MASS) is an all-sky survey. 2MASS images have about 1 arcsecond resolution and were obtained in three broadband filters: J, H, and K_s (K-short). For more detailed information about filters, dates, and coverage, see the 2MASS web page at IRSA or the 2MASS webpage.

BandApproximate central wavelength
J1.25 microns
H1.65 microns
Ks2.17 microns

WISE

Widefield Infrared Survey Explorer (WISE) is a spacecraft that conducted an all-sky survey. WISE mapped the sky in four bands (3.4, 4.6, 12, and 22 microns) with an angular resolution of about 6.1, 6.4, 6.5, and 12.0 arcseconds in the four bands, respectively. For more detailed information about filters, dates, and coverage, see the WISE webpage at IRSA. IMPORTANT NOTE: The date shown in Finder Chart is the average date for the images that go into the coadds from individual frames taken at different times. Near the ecliptic poles, these images may span several months.

BandApproximate central wavelength
W13.4 microns
W24.6 microns
W312 microns
W422 microns

IRAS

The InfraRed Astronomy Satellite (IRAS) is a satellite that flew in 1983 and conducted an all-sky survey in 12, 25, 60, and 100 microns. The angular resolution of the instrument varied between about 0.5 arcmin at 12 microns to about 2 arcmin at 100 microns. The original images have been reprocessed into the IRAS Sky Survey Atlas (ISSA) and IRIS (Improved Reprocessing of the IRAS Survey). For more detailed information about filters, dates, and coverage, see the IRAS webpage at IRSA or the IRAS documentation. For specific information on IRIS, see the IRIS webpage at IRSA.

BandApproximate central wavelength
IRAS-112 microns
IRAS-225 microns
IRAS-360 microns
IRAS-4100 microns

Searching and Results Overview

The only mechanism for searching in Finder Chart is searching by position. One can submit a single target ("single position") or a list of targets ("multiple positions"). (More on searching.)

The search results appear in up to three "panes" (like "window panes"). You can grab and drag the division between the panes to change their relative sizes.

If you searched on only one target with no catalogs, then the only window pane will be that containing the array of images. If you searched on a list of targets, the left pane is a list of the targets on which you searched, and the green highlighted row is the current object being displayed in images in the right pane. When searching on either single or multiple targets, if you ask for it to search catalogs from the initial search page, the catalogs appear in a pane along the bottom of the window. The window panes are all interlinked in that selecting a different row on the left pane changes the contents of the right pane, or selecting an object from the catalog on the bottom changes what is highlighted in the images.

In the window pane with the thumbnail images meeting your search criteria, there may be several things overlaid on each image. The blue circle overlaid by default is the search position you submitted. The images are grouped into rows according to the survey origin -- DSS, SDSS, 2MASS, WISE, and IRAS, depending on which surveys you selected for your search. These images are the real data, and you can interact with these data via the visualization tools. If you searched on catalogs from the main search page, the catalogs are also overlaid on their corresponding images -- 2MASS on 2MASS, WISE on WISE, etc. You can also overlay and plot additional catalogs after you search.

See more on searching for more information about searching.

Visualization Overview

The images meeting your search criteria are shown as the results of the search. The blue circle overlaid by default is the search position you submitted. Some of the various symbols that appear on the 2MASS images by default are image artifacts.

Move your mouse over any image that is returned by your search. Details about the image and, specifically, the pixel beneath your mouse cursor, appear along the top of the window with a variety of useful items. Some information is updated in real time (such as coordinates); some information (such as flux densities) is updated when you stop moving your mouse for a second or two. The image can be interactively investigated in this fashion.

There is a toolbar across the top of the window from which you can interact with the FITS image files as shown -- you can control the stretch, add a coordinate grid, etc. Clicking on the icon that looks like two black arrows zooms enlarges the images to take up more space in the browser, and you can further zoom to make a single image take as much space in the browser as possible. You can scroll through all of the images in this maximally "zoomed-in" view. You can also add or remove overlays (such as coordinates or distances) to your images. See the Visualization section for more on visualization.

If you searched on catalogs from the main search page, the catalogs are also overlaid on their corresponding images -- 2MASS on 2MASS, WISE on WISE, etc. You can also overlay and plot additional catalogs after you search. You can also make plots from catalogs. Click on the blue "Catalogs" tab near the top of the page to initiate this process. See the Catalogs section for more on catalogs.

Downloading Data Overview

There are two ways in which you can download the data.

If you are looking at one object and just want to see all of these, well, finder charts for this object in one place, click on the "PDF" icon in the upper right. This will generate a PDF you can save to your disk or print, just for the object you are currently viewing.

You can also download to disk the individual files in any of a variety of file formats, or if you've searched on multiple targets, you can save a PDF (one object per page). Click on "Prepare Download" in the top of the images pane. A pop-up window asks if you would like to download data for just the current target or all targets, whether you want FITS files, HTML, PDF, or PNG files, and whether or not you want to be emailed when the packaging is done. Click on "Prepare Download" to begin the packaging and data download process -- the download then gets passed to a background job for packaging. See the section on Downloads or the section on the Background Monitor for more information.

User Login Overview

Finder Chart can remember you when you return. See the user registration section for more information.