The mosaic service takes a region of the sky, and builds seamless mosaic image of that part of the sky from a VO-enabled image survey. The service uses the Montage software to reproject the images, then add a linear ramp to each image in order to minimize differences on the overlaps. More details of the Montage software can be found here.

Parameters

The arguments that are sent to the service include:

• -survey: a survey to use to get the images. For example SDSS:r means the r filter of the SDSS survey and DPOSS:J means the J filter of the DPOSS survey.
• -ra: the right ascension of the center of the requested mosaic, in degrees.
• -dec: the declination of the center of the requested mosaic image, in degrees.
• -rawidth and -decwidth may be used to specify the size in degrees of the requested mosaic.
• -atlas: this allows choice of scale. TM-5-TAN-20 means 1 arcsecond per pixel, and TM-5-TAN-17 means 8" per pixel.
• -bgcorr can be set to 1 or 0 for Montage background correction (or not). The default is 0 (no background correction).

Web portal

Nesssi client code

Below is a Python program that can be used to drive the cutout service. First we find the file that contains the list of positions, then build the argument list that contains the desired surveys.

##################################################################
#  Client example: DPOSS
##################################################################
import time
import sys
import nesssi_client as nesssi
# Create a connection
# This uses a proxy certificate , or a key/cert pair from $HOME/.globus if a
# proxy can't be found
nesssiServer=nesssi.client('https://envoy.cacr.caltech.edu:8443/clarens/',debug=0)
params = "-ra 49.1 -dec 60.1 -rawidth 0.5 -decwidth 0.5 -survey DPOSS:J -bgcorr 1"
session = nesssiServer.mosaic.init()
print "Your session ID is %s." % session
nesssiServer.mosaic.run(session, params)
time.sleep(20)
msg = nesssiServer.mosaic.monitor(session)
print msg

Result

Running the monitor function will show a URL which can be monitored until a FITS file appears there, which is the result.