The spot diagram comparison to the left shows the off-axis spot performance for a 16" f3.5 Dream Astrograph (corrected Newtonian) versus a 16" f8.4 Ritchey-Chretien Cassegrain. The Dream Astrograph with 3" coma corrector is on the left of the teal colored "football." The smaller box is 20 microns square and the larger, outer box is 100 microns square. The R-C Cassegrain's spot diagram (the large, teal "football") is in the center of the 100 micron square box. The diagram above illustrates the optical quality at 22.211mm off-axis for both optical designs. This location would be the extreme outer corners of a 24mm x 36mm CCD chip. The Dream Astrograph's RMS radius at this location is 3.3 microns. The R-C Cassegrain's RMS radius at the same 22.211mm off-axis location is 24.6 microns. Click on the graphic to see an enlarged version. The spot diagrams were both based on 16" telescopes. The f8.4 R-C with a f3 primary and 14" of back focus. The Dream Astrograph with a f3.5 primary.

Click here to see the performance of the 1.8x Corrected Barlow.

Click here to see an image taken with a 16" f3.75 using the 3" coma corrector.

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