Extended Sources: Ability To Meet Level 1 Specifications

Photometry - Detailed analysis shows that we meet the specifications under nominal circumstances. However, two problems exist which severely degrade the photometry. First, airglow causes 25% of all scans to violate the Level 1 specification (on H photometry). We will probably need to relax the Level 1 specification as well as rescan the worst airglow scans. Second, J-band background variations in some of the data also cause severely-degraded photometry.

Positions - Are Excellent.

Source Size and Orientation Parameters - These parameters are contaminated by the telescope / camera PSF. Although the position angle is largely correct for most individual galaxies, with errors of only 5-15°, there is a significant bias averaged over all galaxies.

http://spider.ipac.caltech.edu/tchester/2mass/oct98/l1spec2.html Comments and feedback: Tom Chester Last update: 27 October 1998.

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