Focal Length??????????

Discussion in 'Astronomy, Exobiology, & Cosmology' started by Tristan, Aug 4, 2001.

  1. Tristan Leave your World Behind Valued Senior Member

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    What does the Focal length affect as far as telescopes go?? I thought it was just 2 types really, one for Visual observing and one for astrophotography. Help me and anybody else who needs to know.

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  3. Chagur .Seeker. Registered Senior Member

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  5. Caronte Registered Member

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    The focal length its about how many space is between the componets to make focus. For example an 16" SCT has something like 4500mm wile a 8" has 2200mm, but both at F10, that means that the same light passes thru each one but the proyection in the 16" is bigger, in astrophotography you often compress the image to get (for example) F6.5, that means that you are going to reduce the time of exposures, increase the light at the cost of getting a smaller image.
     
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