Preliminary lens table for SLAS-SPOC Clark Refractor
Sort order: Increasing magnification, decreasing TFOV
List has not be verified with drift measurements

Scope Aperature_mm Aperature_in Eyepiece focal length mm Barlow AFOV (dec_degrees) Telescope_fl_mm Magnification TFOV dec_degs TFOV arc_min TFOV arc_sec Dawes Limit arcsec 116/Dmm Rayleigh Limit arcsec 138/Dmm Mag/inch Mag type Used for
Clark 7.87" F/16.8 199.89 7.87 0 1 50.8 3360 1.0 0.9 52 3119 0.58 0.97 0.1 Very low Direct projection astrophotography
Clark 7.87" F/16.8 199.89 7.87 52 1 50 3360 64.6 0.8 46 2786 0.58 0.97 8.2 Low Large angular size objects
Clark 7.87" F/16.8 199.89 7.87 40 1 54 3360 84.0 0.6 39 2314 0.58 0.97 10.7 Medium Small clusters and galaxies
Clark 7.87" F/16.8 199.89 7.87 32 1 52 3360 105.0 0.5 30 1783 0.58 0.97 13.3 Medium Small clusters and galaxies
Clark 7.87" F/16.8 199.89 7.87 40 2 54 3360 168.0 0.3 19 1157 0.58 0.97 21.3 High Planetary and lunar details
Clark 7.87" F/16.8 199.89 7.87 20 1 52 3360 168.0 0.3 19 1114 0.58 0.97 21.3 High Planetary and lunar details
Clark 7.87" F/16.8 199.89 7.87 32 2 52 3360 210.0 0.2 15 891 0.58 0.97 26.7 High Planetary and lunar details
Clark 7.87" F/16.8 199.89 7.87 15 1 52 3360 224.0 0.2 14 836 0.58 0.97 28.5 High Planetary and lunar details
Clark 7.87" F/16.8 199.89 7.87 40 3 54 3360 252.0 0.2 13 771 0.58 0.97 32.0 Very high Specific planetary lunar detail
Clark 7.87" F/16.8 199.89 7.87 12 1 52.5 3360 280.0 0.2 11 675 0.58 0.97 35.6 Very high Specific planetary lunar detail
Clark 7.87" F/16.8 199.89 7.87 32 3 52 3360 315.0 0.2 10 594 0.58 0.97 40.0 Very high Specific planetary lunar detail
Clark 7.87" F/16.8 199.89 7.87 12 1 45 3360 280.0 0.2 10 579 0.58 0.97 35.6 Very high Specific planetary lunar detail
Clark 7.87" F/16.8 199.89 7.87 20 2 52 3360 336.0 0.2 9 557 0.58 0.97 42.7 Extreme Double stars
Clark 7.87" F/16.8 199.89 7.87 9 1 52 3360 373.3 0.1 8 501 0.58 0.97 47.4 Extreme Double stars
Clark 7.87" F/16.8 199.89 7.87 8 1 52 3360 420.0 0.1 7 446 0.58 0.97 53.4 Extreme Double stars
Clark 7.87" F/16.8 199.89 7.87 15 2 52 3360 448.0 0.1 7 418 0.58 0.97 56.9 Extreme Double stars
Clark 7.87" F/16.8 199.89 7.87 20 3 52 3360 504.0 0.1 6 371 0.58 0.97 64.0 Extreme Double stars
Clark 7.87" F/16.8 199.89 7.87 12 2 52.5 3360 560.0 0.1 6 338 0.58 0.97 71.2 Extreme Double stars
Clark 7.87" F/16.8 199.89 7.87 6 1 52 3360 560.0 0.1 6 334 0.58 0.97 71.2 Extreme Double stars
Clark 7.87" F/16.8 199.89 7.87 12 2 45 3360 560.0 0.1 5 289 0.58 0.97 71.2 Extreme Double stars
Clark 7.87" F/16.8 199.89 7.87 15 3 52 3360 672.0 0.1 5 279 0.58 0.97 85.4 Empty Nearly useless
Clark 7.87" F/16.8 199.89 7.87 9 2 52 3360 746.7 0.1 4 251 0.58 0.97 94.9 Empty Nearly useless
Clark 7.87" F/16.8 199.89 7.87 12 3 52.5 3360 840.0 0.1 4 225 0.58 0.97 106.7 Empty Nearly useless
Clark 7.87" F/16.8 199.89 7.87 4 1 52 3360 840.0 0.1 4 223 0.58 0.97 106.7 Empty Nearly useless
Clark 7.87" F/16.8 199.89 7.87 8 2 52 3360 840.0 0.1 4 223 0.58 0.97 106.7 Empty Nearly useless
Clark 7.87" F/16.8 199.89 7.87 12 3 45 3360 840.0 0.1 3 193 0.58 0.97 106.7 Empty Nearly useless
Clark 7.87" F/16.8 199.89 7.87 6 2 52 3360 1120.0 0.0 3 167 0.58 0.97 142.3 Empty Nearly useless
Clark 7.87" F/16.8 199.89 7.87 9 3 52 3360 1120.0 0.0 3 167 0.58 0.97 142.3 Empty Nearly useless
Clark 7.87" F/16.8 199.89 7.87 8 3 52 3360 1260.0 0.0 2 149 0.58 0.97 160.1 Empty Nearly useless
Clark 7.87" F/16.8 199.89 7.87 4 2 52 3360 1680.0 0.0 2 111 0.58 0.97 213.5 Empty Nearly useless
Clark 7.87" F/16.8 199.89 7.87 6 3 52 3360 1680.0 0.0 2 111 0.58 0.97 213.5 Empty Nearly useless
Clark 7.87" F/16.8 199.89 7.87 4 3 52 3360 2520.0 0.0 1 74 0.58 0.97 320.2 Empty Nearly useless
Knisely's Table of Useful Magnifications
Units: Magnification per inch of aperture

Low Mag Per Inch High Per Inch Low Exit Pupil mm High Exit Pupil mm Useful Mag Description Used For
0.0 3.7 N/a N/a Very low Direct projection astrophotography
3.7 9.9 6.9 2.5 Low Large angular size objects
10.0 17.9 2.6 1.4 Medium Small clusters and galaxies
18.0 29.9 1.3 0.8 High Planetary and lunar details
30.0 41.9 0.7 0.6 Very high Specific planetary lunar detail
42.0 75.0 0.5 0.3 Extreme Double stars
76.0 200.0 0.2 0.0 Empty Nearly useless

Source: Adapted from Knisely's Useful Magnifications from D. Knisely, 5/14/2004 sci.astro.amateur Usenet post, Thread, "Eyepiece Advice"

Prepared by: fisherka@csolutions.net 5/2006