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THE FEUTEX TOOLKIT

Telescope Obstruction and Light Collection

Estimate clear collecting area and the fractional loss from a central obstruction.

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FormulaClear collecting area = PI*(d**2-o**2)/4; Blocked area = 100*(o/d)**2; Equal-area unobstructed diameter = sqrt(d**2-o**2)
Sources and model references

Worked example

Inputs

Primary diameter
200 mm
Obstruction diameter
50 mm

Expected results

Clear collecting area
29452.43113 mm²
Blocked area
6.25 %
Equal-area unobstructed diameter
193.6491673 mm

Load the example in the workspace to reproduce these results. Display rounding does not change the underlying calculation.

How to use this tool

  1. Estimate clear collecting area and the fractional loss from a central obstruction.
  2. Set primary diameter, obstruction diameter in the indicated units.
  3. Calculate and compare clear collecting area, blocked area, equal-area unobstructed diameter.

Try this example

{
  "d": 200,
  "o": 50
}

Accuracy and scope

Idealized educational model. Enter measured values in the displayed units; real systems may require additional corrections.

Is my data uploaded?

This tool runs locally in your browser. Input and output are not sent to a processing server. Copy or download your result before leaving the page.