A simple user interface provides access to the processed PanSTARRS images. Both warp (single epoch) and stack (combined) images are available for the grizy filters in the 3PI survey. The stack images are also combined to create color images. Images may be extracted using an RA+Dec position or using an object name. The resulting cutout images (postage stamps) are available as JPEG images within the web browser or as FITS images. The interface also provides access to download skycell images covering larger sky regions, along with an interactive display for browsing larger sky regions. Finally, there are web services that can be used for access to the images via scripts.
The web interface
The PS1 images are accessible through http://plpsipp1v.stsci.edu/cgi-bin/ps1cutouts. (This is a temporary URL that will change in the near future.) The interface has a text box to enter a position or object name plus a few other options. Type an object name or position into the box and click Submit:
The search string can be a name that is recognized by NED or SIMBAD (e.g., "ring nebula" as above) or a position in various formats (RA and Dec in degrees, hh mm ss +dd mm ss, h:m:s d:m:s, etc.). A PanSTARRS image identifier (e.g., skycell.2069.026) is also accepted and is translated to the central position of that image.
The labels above each image identify the image type (stack or warp), the image identifier (these come from skycell.2069.026), and the filter. For warp images the labels also include the modified Julian date of the observations.
Changing the parameters
The default parameters for the search return 240x240 pixel cutout images (=1x1 arcmin for the PS1 scale of 0.25 arcsec/pixel), including a color image and all five filters, grizy. The filters used for the color image are the reddest (y), the bluest (g), and the middle image (i).
The parameters allow changing the defaults:
|Filters||Select a subset of the filters using check boxes|
|File types||Include the warp (single epoch) images in addition to or instead of the stack images|
|Cutout size||Specify the extracted image size in pixels. The conversion to arcsec is shown. If this size is large, the cutout image may reach the edge of the PS1 image; in that case the pixels off the edge are filled with blanks.|
|Output size||Select a fixed size for the display images. The cutout is scaled to the selected size. This can be used either to shrink the images when the cutout size is large or to expand the image for small cutouts.|
As an example, here are images for the Ring Nebula with the cutout size increased to 512 pixels (128 arcsec), the output size set to 256 pixels (so the JPEG scale is 0.5 arcsec/pixel), and the gri filters selected (which changes the color image as well):
Warp (single epoch) images
If the warp box is checked, the results include all single-epoch PS1 images that overlap the requested sky position. Here is an example for the Ring Nebula g-band images:
The result page shows the stack image(s) followed by all the warp images. The warps are grouped by filter (grizy) and are sorted by epoch of observation. Note that the individual warps often show many regions of missing pixels due to gaps between detectors, bad pixel regions, etc. These bad pixels are rejected during stacking, and the warp pointing centers are dithered so that the final quality of the stack images is generally very good. Obviously users will need to take care in using the single-epoch images!
There are usually a large number (~20) of warp images for each filter. Some of the warp images are completely blank because the actual sky coverage for the exposure contributing to a particular skycell does not necessarily cover the cutout image region. Currently our PS1 image database does not have a detailed map of the precise sky coverage for individual exposures, so the warp images that lack sky coverage in a region are not known before the cutout is extracted. That will be improved in future versions of the interface.
Access to FITS images and interactive image display
Describe the titles above the cutouts.
Describe the FITS/FITS-cutout/Display links.
Describe the interactive display.
Scripted extraction of cutouts
Describe how to extract images using a script. Give a Python script that shows how it works.
Plans for future additions
We plan to make a number of improvements and additions to this interface in the future. Suggestions for other additions are also welcome (send to email@example.com).
- Fill in blank pixels from neighboring skycells.
- Give user the ability to select which filters are used to create the color image.
- Give user the ability to adjust the contrast in the cutout images.
- Provide an interface with easy access to corresponding cutouts from all the other associated images (weights, data quality images, etc.)
- Include more accurate footprints for the warp sky coverage in the database so that blank warp cutouts are rare.
Color 256x256 arcsec image of M8 using the PS1 gri filters created using the image cutout interface.