Telescope Secondary Size, Strehl Ratio Spread Sheet

Mirror Diameter (inches) user input
Focal Ratio (f/#) user input
Focal Length (inches)
Focal Length (mm)
Secondary (inches) user input
Central Obstruction (%)
Airy Disk (%)
Strehl Ratio
Focuser Height (inches) user input
Tube Radius (inches) user input
Secondary to Focal Point (inches)
Circle of Full Illumination (inches)
s'
Secondary mirror offset (inches)
Image Size (minutes) on 35mm


This form will help you determine the optimum diagonal size for your telescope. Where needed, fill in "user input" fields and click the [Calculate] button. The default values are from our observatory's 15" telescope. Values from other members telescopes are listed below.

Mirror Diameter (inches)

13.10

14.80

23.50

Focal Ratio (f/#)

4.50

5.57

4.50

Focal Length (inches)

58.95

82.44

105.75

Focal Length (mm)

1497.33

2093.87

2686.05

Focuser Height (inches)

2.50

1.50

1.50

Tube Radius (inches)

8.00

9.00

13.20

Secondary to Focal Point (inches)

10.75

10.75

14.95

Secondary (inches)

3.21

2.80

4.18

Aperature (sq inches)

134.78

172.03

433.74

size of moon

0.53

0.74

0.95

 

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This web page was last updated 07/09/16