The above table indicates eyepiece magnification. Also shows exit pupil. A negative magnification number means the eyepiece either goes below 5x to the inch, or above 50x to the inch. In other words, overkill.
Where needed, fill in "user input" fields and click the [Calculate] button. To compute focal length, enter mirror diameter. To computer mirror diameter, enter focal length. In ether case, you must enter focal ratio. 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 |
11 |
|
Focal Ratio (f/#) |
4.50 |
5.57 |
4.50 |
10 |
|
Focal Length (inches) |
58.95 |
82.44 |
105.75 |
110.24 |
|
Focal Length (mm) |
1497.33 |
2093.87 |
2686.05 |
2800 |
|
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 |
3.75 |
|
Aperature (sq inches) |
134.78 |
172.03 |
433.74 |
|
|
size of moon |
0.53 |
0.74 |
0.95 |
For more detail on individual eyepiece performance, click here.
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This web page was last updated 04/22/20