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Below some 86° and 100° coma correcting eyepiece designs. For each eyepiece you'll see the lens configuration, the ray trace results for 10 field angles, the spot diagrams at the 10 field angles, and the Eyepiece Quality Score (lower is better). In the spot diagrams you'll find in the upper right two circles of 2' and 5' diameter that are convenient for evaluating the quality of the design (for reference, the maximum resolution of the human eye is 1'). Star images that fit inside a 2' circle are virtually perfect, inside a 5' circle are very good. The designs have mostly been optimized at f/4. They will still work very well at f/3, obviously with larger aberrations because of the
faster light cone. At f/5 the eyepieces will perform even better than at f/4.
32 mm 81° Coma Correcting EyepieceThis eyepiece has a huge field stop of 45 mm, about the largest that you can fit in a 2 inch barrel. It is very well corrected and will deliver pinpoint star images right to the edge of the field. Layout:  Ray trace results:  Angle Field Spot Circle RMS Relief Curvature Vignet Power rad/tan 0.00° 0.04° 0.7'x 0.7' 0.26' 20.11 0.082 /m 0.00% 37.44/ 37.44 0.12° 4.45° 0.7'x 0.8' 0.31' 20.05 0.108 /m 0.00% 37.42/ 37.39 0.24° 8.90° 0.8'x 1.1' 0.40' 19.85 0.186 /m 0.00% 37.37/ 37.26 0.36° 13.35° 0.9'x 1.4' 0.48' 19.52 0.312 /m 0.00% 37.33/ 37.05 0.48° 17.79° 0.9'x 1.7' 0.55' 19.09 0.479 /m 0.00% 37.33/ 36.78 0.60° 22.24° 0.9'x 2.0' 0.64' 18.57 0.675 /m 0.00% 37.48/ 36.45 0.71° 26.72° 0.8'x 2.5' 0.80' 17.99 0.870 /m 0.00% 37.85/ 36.08 0.83° 31.26° 1.0'x 3.3' 1.01' 17.40 1.007 /m 0.00% 38.44/ 35.69 0.95° 35.86° 1.9'x 3.9' 1.24' 16.89 1.008 /m 0.00% 38.66/ 35.25 1.07° 40.35° 1.0'x 4.5' 1.30' 17.00 0.985 /m 17.74% 36.18/ 34.64 Eyepiece Quality Score: Spot Diagram 0.002034 Power Target 0.000027 Eye Relief 0.000002 SA Exit Pupil 0.000021 Field Curvature 0.000319 Distortion-AMD 0.000047 Vignetting 0.000162 Size 0.001070 Glass mass 0.000353 Cost 0.000698 ========================= Total Score 0.004733 This eyepiece produces a true field that is nearly 25% larger than the Televue Nagler 31 in a Paracorr, in a compact package with the largest lens 65 mm in diameter.  28 mm 86° Coma Correcting EyepieceProviding a 41.5 mm field stop with tight stars right to the edge, without distortion, this eyepiece would provide the maximum 7 mm exit pupil in f/4 Newtonian telescopes, like the original 28 mm Pretoria eyepiece (but with 86° instead of 50° apparent field of view!). Layout:  Ray trace results:  Angle Field Spot Circle RMS Relief Curvature Vignet Power rad/tan 0.00° 0.04° 0.9'x 0.9' 0.32' 19.41 0.095 /m 0.00% 42.72/ 42.72 0.11° 4.70° 0.9'x 1.1' 0.42' 19.35 0.128 /m 0.00% 42.70/ 42.67 0.22° 9.39° 1.1'x 1.6' 0.60' 19.18 0.224 /m 0.00% 42.67/ 42.51 0.33° 14.09° 1.4'x 2.2' 0.75' 18.90 0.374 /m 0.00% 42.66/ 42.26 0.44° 18.78° 1.5'x 2.4' 0.84' 18.53 0.561 /m 0.00% 42.73/ 41.93 0.55° 23.49° 1.7'x 2.7' 0.89' 18.07 0.757 /m 0.00% 42.97/ 41.53 0.66° 28.25° 1.7'x 3.0' 1.00' 17.54 0.918 /m 0.00% 43.48/ 41.09 0.77° 33.07° 1.9'x 3.8' 1.25' 16.96 0.973 /m 0.00% 44.23/ 40.60 0.88° 37.97° 2.7'x 4.8' 1.54' 16.43 0.838 /m 0.00% 44.64/ 40.06 0.99° 42.77° 1.4'x 4.9' 1.43' 16.44 0.471 /m 20.61% 41.38/ 39.30 Eyepiece Quality Score: Spot Diagram 0.002633 Power Target 0.000078 Eye Relief 0.000064 SA Exit Pupil 0.000006 Field Curvature 0.000232 Distortion-AMD 0.000062 Vignetting 0.000244 Size 0.001050 Glass mass 0.000366 Cost 0.000688 ========================= Total Score 0.005424 This eyepiece provides a larger field of view with less distortion than the Nagler 31 in Paracorr. It delivers its goodies in a much lighter and more convenient package:  24 mm 86° Coma Correcting EyepieceProviding a 36 mm field stop with tight stars right to the edge, without distortion, this eyepiece would provide a 15% larger field than the Televue Ethos 21 plus Paracorr combo the author is currently using on his 1100 mm f/3.6 telescope, in a significantly lighter and more compact package. Layout:  Ray trace results:  Angle Field Spot Circle RMS Relief Curvature Vignet Power rad/tan 0.00° 0.05° 0.6'x 0.6' 0.26' 19.81 0.094 /m 0.00% 49.92/ 49.92 0.10° 4.77° 0.7'x 0.9' 0.34' 19.75 0.128 /m 0.00% 49.87/ 49.85 0.19° 9.53° 0.8'x 1.4' 0.48' 19.57 0.226 /m 0.00% 49.72/ 49.62 0.29° 14.27° 1.0'x 1.8' 0.61' 19.27 0.376 /m 0.00% 49.52/ 49.26 0.38° 18.99° 1.1'x 2.2' 0.70' 18.87 0.556 /m 0.00% 49.34/ 48.78 0.48° 23.70° 1.1'x 2.4' 0.76' 18.37 0.736 /m 0.00% 49.29/ 48.21 0.57° 28.42° 1.1'x 2.9' 0.89' 17.80 0.871 /m 0.00% 49.46/ 47.56 0.67° 33.16° 2.1'x 4.0' 1.26' 17.21 0.916 /m 0.00% 49.86/ 46.86 0.76° 37.94° 3.1'x 5.0' 1.67' 16.68 0.867 /m 0.00% 50.02/ 46.08 0.86° 42.67° 1.0'x 4.6' 1.36' 16.67 0.899 /m 18.13% 48.32/ 45.15 Eyepiece Quality Score: Spot Diagram 0.002422 Power Target 0.000031 Eye Relief 0.000021 SA Exit Pupil 0.000016 Field Curvature 0.000148 Distortion-AMD 0.000012 Vignetting 0.000173 Size 0.001051 Glass mass 0.000330 Cost 0.000739 ========================= Total Score 0.004943 It is interesting to compare the performance of this eyepiece at various focal ratios. The image below shows the spot diagrams at f/4, f/3 and f/5. Click on the image for a full-size version.  In practice you'll probably not use it at f/3, it would produce a 8 mm exit pupil. Then again, you might! 20 mm 100° Coma Correcting EyepieceProviding a 35 mm field stop, this would be the ultimate wide-field eyepiece for very fast Newtonian telescopes. It would provide a 10% larger field than the Ethos 21 in Paracorr combo, in a lighter and more compact package. The eyepiece has been optimized to provide a generous eye relief between 17 and 20 mm which will contribute to the observation comfort. Layout:  Ray trace results:  Angle Field Spot Circle RMS Relief Curvature Vignet Power rad/tan 0.00° 0.06° 1.3'x 1.3' 0.57' 20.13 0.241 /m 0.00% 59.88/ 59.88 0.09° 5.54° 1.4'x 1.5' 0.59' 20.09 0.298 /m 0.00% 59.91/ 59.80 0.19° 11.09° 1.5'x 1.8' 0.67' 19.94 0.455 /m 0.00% 59.99/ 59.54 0.28° 16.65° 1.5'x 2.2' 0.77' 19.69 0.677 /m 0.00% 60.16/ 59.13 0.37° 22.23° 1.6'x 2.6' 0.88' 19.34 0.906 /m 0.00% 60.45/ 58.55 0.46° 27.84° 1.9'x 3.3' 1.10' 18.86 1.069 /m 0.00% 60.80/ 57.82 0.56° 33.48° 3.1'x 4.8' 1.58' 18.25 1.107 /m 0.00% 60.93/ 56.92 0.65° 39.09° 4.1'x 5.8' 1.97' 17.49 1.039 /m 0.00% 59.93/ 55.76 0.74° 44.48° 3.2'x 4.9' 1.62' 16.63 1.106 /m 0.00% 56.11/ 54.22 0.83° 49.56° 3.1'x 5.7' 1.89' 16.87 0.788 /m 15.33% 60.06/ 52.35 Eyepiece Quality Score: Spot Diagram 0.003386 Power Target 0.000021 Eye Relief 0.000031 SA Exit Pupil 0.000083 Field Curvature 0.000211 Distortion-AMD 0.000074 Vignetting 0.000107 Size 0.001181 Glass mass 0.000633 Cost 0.001153 ========================= Total Score 0.006879 A comparison of the eyepiece with the author's Televue Ethos 21 in Paracorr:  | ||||
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