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Stellarium Occulars Plugins Question - camera lens diameter

planetarium software
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#1 erpagris

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Posted 26 May 2020 - 08:53 PM

Hello,

 

I am trying to find out the value to enter in the diameter field under the telescopes tab for a photo lens. When I search on lens diameter for a specific lens, I get results on how to determine the filter size. Is that the same as the lens diameter? On some of my lenses, the lens diameter looks quite a bit smaller than the filter thread diameter. I would like to be able to simulate what images would look like using a camera lens in addition to of a telescope.

 

Thanks,

Eric


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#2 LarsMalmgren

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Posted 26 May 2020 - 10:09 PM

I use the relation between focal length and f-number to calculate the diameter.

f = D * N, where F is focal length & N is f-number.

 

so

f = D * N  <==>  D = f / N  <==>  N = f / D.

 

For example a 100 mm f/4 lens, the diameter is 25 mm.

The front lens can be bigger since this is the diameter of the aperture stop inside the lens.

 

 

I think Stellarium uses this to calculate the angular resolution of the optics so if you're mostly interested in the field of view box then you can pretty much put in any diameter.


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#3 erpagris

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Posted 27 May 2020 - 12:54 PM

Thank you very much. That will be helpful.

Eric




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