From jack.f.eastman@lmco.com Mon May 8 15:45:04 2000 Subject: 20" Chamberlin, analytic results To: gjonesdas@juno.com, rstencel@du.edu, Greg.Marino@windsorind.com, rpearson@ecentral.com Cc: gene.cross@lmco.com, Skyhawk-@mindspring.com, victor.nikolashin@lmco.com, telscope@europa.com, lensmaker@ap.net, rclark@speclab.cr.usgs.gov, rsinnott@skypub.com All... Here's some results of ZEMAX fiddling with a "Chamberlin-like lens" The assumptions were that it is a Littrow design, sort of, and the thicknesses and spacing are my best guesses from Greg's measurements and our looking at the lens, poking laser pointer light through it and all. I gave it my best guess, and used GENII to optimize the initial Littrow formula. I allowed R4 to become slightly convex, as opposed to fiddling with aspherics, and obtained ~1/55 wave performance at W=587.6nm. The glass was assumed to be the good old ubiquitous BK7 and F4. Chasing N ad V from Church's S&T article (Mar 1982, Thanx, Roger!) for the other AC lenses (36" and 40") hasn't gotten me any closer, quite yet. Next try, French glass instead of the good old Schott. First, at the optimum visual configuration: <<...OLE_Obj...>> <<...OLE_Obj...>> Above... Wavefront at W=550nm, full scale is .01 waves (!!), showing slight overcorrection, 1/200 wave (!!) This is 4X better than the GENII analysis which gives 1/55 wave undercorrected! Believe it or not, this is due to a slight difference in the wavelengths for the analysis. GENII was at 587.6. I changed it to 550, refocused and the two are now indistinguishable. (whew!) The nasty looking OPD's to the right are 1 deg. off axis, and is primarily coma Next is the color/focus curve. Below, system data. System/Prescription Data File : C:\ZEMAX\SAMPLES\CHAMBER20in.ZMX Title: Chamberlin 20" Visual Mode Date : MON MAY 8 2000 LENS NOTES: Apologies to Alvan Clark, & C. A. R. Lundin ! GENERAL LENS DATA: Surfaces : 10 Stop : 1 System Aperture : Entrance Pupil Diameter = 508 Ray aiming : Off Apodization :Uniform, factor = 0.00000E+000 Eff. Focal Len. : 7797.516 (in air) Eff. Focal Len. : 7797.516 (in image space) Back Focal Len. : 7615.825 Total Track : 7730.835 Image Space F/# : 15.34944 Para. Wrkng F/# : 15.34944 Working F/# : 15.34165 Image Space N.A.: 0.03255721 Obj. Space N.A. : 2.54e-008 Stop Radius : 254 Parax. Ima. Hgt.: 136.1061 Parax. Mag. : 0 Entr. Pup. Dia. : 508 Entr. Pup. Pos. : 0 Exit Pupil Dia. : 502.3042 Exit Pupil Pos. : -7710.098 Field Type : Angle in degrees Maximum Field : 1 Primary Wave : 0.55 Lens Units : Millimeters Angular Mag. : 1.011339 Fields : 2 Field Type: Angle in degrees # X-Value Y-Value Weight 1 0.000000 0.000000 1.000000 2 0.000000 1.000000 1.000000 Vignetting Factors # VDX VDY VCX VCY 1 0.000000 0.000000 0.000000 0.000000 2 0.000000 0.000000 0.000000 0.000000 Wavelengths : 10 Units: Microns # Value Weight 1 0.350000 1.000000 2 0.400000 1.000000 3 0.450000 1.000000 4 0.500000 1.000000 5 0.550000 1.000000 6 0.600000 1.000000 7 0.650000 1.000000 8 0.700000 1.000000 9 0.750000 1.000000 10 0.800000 1.000000 Now, the spacing is increased by 150mm, to produce the "blue" photographic correction: <<...OLE_Obj...>> <<...OLE_Obj...>> Above... Best wavefront plot @W=450nm, Now ~3 waves undercorrected (!) At this setting, the spherical overwhelms the off axis coma, so the edge of the field looks "better". It is just that the axis is a whole lot worse. Next, the color/focus plot at the Pg setting. System/Prescription Data File : C:\ZEMAX\SAMPLES\CHAMBER20in.ZMX Title: Chamberlin 20" Photographic mode... Date : MON MAY 8 2000 LENS NOTES: More apologies to Alvan Clark, & C. A. R. Lundin ! GENERAL LENS DATA: Surfaces : 10 Stop : 1 System Aperture : Entrance Pupil Diameter = 508 Ray aiming : Off Apodization :Uniform, factor = 0.00000E+000 Eff. Focal Len. : 7325.164 (in air) Eff. Focal Len. : 7325.164 (in image space) Back Focal Len. : 6818.504 Total Track : 7083.504 Image Space F/# : 14.41961 Para. Wrkng F/# : 14.41961 Working F/# : 14.38665 Image Space N.A.: 0.03465416 Obj. Space N.A. : 2.54e-008 Stop Radius : 254 Parax. Ima. Hgt.: 127.8612 Parax. Mag. : 0 Entr. Pup. Dia. : 508 Entr. Pup. Pos. : 0 Exit Pupil Dia. : 489.2366 Exit Pupil Pos. : -7054.603 Field Type : Angle in degrees Maximum Field : 1 Primary Wave : 0.55 Lens Units : Millimeters Angular Mag. : 1.038352 Fields : 2 Field Type: Angle in degrees # X-Value Y-Value Weight 1 0.000000 0.000000 1.000000 2 0.000000 1.000000 1.000000 Vignetting Factors # VDX VDY VCX VCY 1 0.000000 0.000000 0.000000 0.000000 2 0.000000 0.000000 0.000000 0.000000 Wavelengths : 10 Units: Microns # Value Weight 1 0.350000 1.000000 2 0.400000 1.000000 3 0.450000 1.000000 4 0.500000 1.000000 5 0.550000 1.000000 6 0.600000 1.000000 7 0.650000 1.000000 8 0.700000 1.000000 9 0.750000 1.000000 10 0.800000 1.000000 Cheers... FJE