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Knowledgebase: IRAC
What is the accuracy of measuring the relative separation between two sources in an IRAC observation?
Posted by Seppo Laine on 21 November 2008 11:54 AM
The relative accuracy of measuring the separation of two sources in IRAC images is probably better than 0.3" for source with signal-to-noise ratio greater than 10 on the same BCD image. One of the main factors limiting the accuracy is the uncertainty in the knowledge of the distortion, which we think is known to 0.1" or better. If the two sources are in different BCDs, and the position difference is being measured on the mosaic, then the error will be dominated by the error in the pointing refinement. We've measured this to be ~0.3" for frames where the pointing refinement has worked well. For a difference this should be multiplied by sqrt(2), but that's probably a little conservative as the errors in any patch of sky are probably correlated.