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You are here: Home Telescopes Magellan Instruments PANIC Panic online documentation Observer Information Panic Observer's Manual Observations Image Quality and Distortion

Image Quality and Distortion


PANIC produces excellent images. The best image quality recorded to date is 0.20'' FWHM in the Ks filter. If you have observed yet better image quality, please let us know!

PANIC does have some optical distortion that becomes important for dither sequences with step sizes greater than about 5''. The distortion is purely radial, that is it is symmetric about the center of the field, and has been well-characterized from a ZEMAX model of the instrument's optical design. The percent distortion at a distance r arcseconds from the center of the field is:

p = a0 + a1*r + a2*r2     (2)

where a0 = 8.870579e - 03, a1 = - 1.618900e - 03, and a2 = 2.379338e - 04. The distortion is in the sense that objects will appear further from the center of the field than they actually are (pincushion distortion).
It is important to correct for this distortion when combining multiple dithers. For example, a 10 - 20'' dither step in a five or nine position dither sequence will lead to a couple pixel shifts in the centroids of objects near the corners of the array. The above equation corrects for the distortion to a better than a tenth of a pixel. The IRAF script distcor in the panic package implements this distortion correction.

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