# Image Quality

• Useful guide to evaluate the image quality and frequent optical aberrations (information in Spanish).
• 4M PF IMAGING:
• See here the as-per-design image quality at PF with MosaicII. This is based on diffraction encircled energy plots with the optical model in Zemax. Note the residual coma+trefoil pattern in the corners, well confirmed by the individual field aberration maps below. So far, to my knowledge, the best image achieved at PF with MosaicII (july 6th, 2000) had a fwhm of 0.54" (15sec, R filter). There are several other cases around 0.60" in long exposures.
• Residual field aberrations in the optical design of the PFADC: coma, astigmatism, trefoil, there is no quadrafoil left over, some small amount of 5th order terms). For reference, MosaicII CCD array is 123mm square. These maps are built with the Zernike coefficients delivered by Zemax. The quadratic sum of the 3 main aberrations in the corners sum up to a d80 = 0.48", rather close to the diffraction encircled energy d80 = 0.53" given by Zemax (see plot above). Note that the minimum coma field point is not the field center due to the assymmetry of the ADC prism angles (1.17 and 1.37deg respectively). A 5 arcsec tilt of M1 is required to zero the coma on-axis (see result). In theory, the effect of the ADC is only to produce a rotation of these patterns around the field center.
• Ellipticity measurements of Mosaic images.
• Depth of focus with Mosaic. You can deduce from this graph how well you need to focus initially and then watch out the temperature changes.
• See the effects of not using the ADC at different wavelengths and elevations on this plot.
• Infrared Side Port Imager (ISPI): spot diagrams in J band, H band, K band (fields are R, 0.85R, 0.70R, 0.50R, 0.35R and 0, where R is half the diagonal of the array). Diffraction encircled energy in J band, H band, K band. Through focus sequences in J band, H band, K band. Plate scale is 0.31 arcsec/pixel. Boxes are 2x2 pixels. No interband refocusing. Previous optimization (RMS spot size based) yielded the spot diagrams currently on the ISPI web page and the following EE at J band, H band, K band.
• IQ Status 2009 Summary
• IQ Status 2010 in Blanco 4.0-m Optical Status 2010