• Download M17_GBT.fits: FITS file, 366 KB

• FITS File, 366KB Download M17_GBT.fits

• Other images may be downloaded through the NRAO Image Gallery: M17

Image Data

Observing Information

• Scanning in the RA direction, 40 seconds per scan.
• 30 arcsec spacing in Declination between scans.

• Scanning in the RA direction, 45 seconds per scan.
• 30 arcsec spacing in Declination between scans; 180 stripes.
• GBT beam size at 8.4 GHz (HPBW) is about 88 arcsec.
• Integration 0.1 second per 12 arcsec pixel in the RA direction.

Processing

• Calibration and gridding was done by the "aips++" package.
• A linear baseline was subtracted from each scan.
• Some smoothing was done to minimize the stripe artifacts.
• Edge areas were blanked; these pixels have the value "NAN" in the FITS file.

Map Information

• Values in Jy/beam; 306x292 pixels; pixel size 18x18 arcsec.
• Max value in map; 54.0 Jy/beam
• rms per pixel in blank areas about 0.01 Jy/beam.
• Coordinates are of epoch B1950.
• (yes, the header information in the FITS file is woefully inadequate!)

Credit: this image was taken during GBT telescope commissioning in February 2002;

Credit: this image was taken during GBT telescope commissioning in February 2002;

%META:TOPICINFO{author="FrankGhigo" date="1204819740" format="1.0" version="1.1"}% %META:TOPICPARENT{name="GBTImages"}%

GBT Image of M17, the Omega Nebula

• Download M17_GBT.fits: FITS file, 366 KB

Image Data

• Observed with the GBT on February 8, 2002 as part of commissioning tests.
• continuum observation at a frequency of 8.4 GHz with a bandwidth of 320 MHz
• recorded with the GBT "DCR" (digital continuum receiver).
• Mapping over a 1.5x1.5 degree area by "on-the-fly" method.
• Scanning in the RA direction, 40 seconds per scan.
• 30 arcsec spacing in Declination between scans.

Calibration

No corrections for atmospheric absorption were made, but at 8.4 GHz these probably do not amount to more than 2-3%. Our recollection is that the observations were made on an excellent clear night.

Our most optimistic guess is that the calibration is maybe as good as 5%, and probably good to better than 10%.

Credit: this image was taken during GBT telescope commissioning in February 2002;
investigators: Frank Ghigo, Dana Balser, Ron Maddalena, Glen Langston.
The National Radio Astronomy Observatory is a facility of the National Science
Foundation operated under cooperative agreement by Associated Universities, Inc.

-- FrankGhigo - 06 Mar 2008

with

%META:FILEATTACHMENT{name="M17image_small.gif" attr="h" comment="M17Image Thumbnail " date="1204820325" path="M17image_small.gif" size="9085" user="FrankGhigo" version="1.1"}% %META:FILEATTACHMENT{name="M17_GBT.fits" attr="" comment="M17 Image, FITS file, 366 KB" date="1204820443" path="M17_GBT.fits" size="365760" user="FrankGhigo" version="1.1"}%