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Thread: Magnification with fixed camera body

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    I just bought an Olympus Pen E-PM1, which uses the Four-Thirds lens system. For Four-Thirds, the fixed number should be different from the number 50 given by AustinPSD. On my camera the sensor size is 17.3mm x 13mm, and the maximum resolution is 4032 x 3024 pixels, so, according the the calculator Yoddha linked to (Thank you!), the magnification with my Meade ETX-80AT (with a 400mm focal length) should be about X18.5, which sounds about right judging from the images I'm getting. So if I understand correctly, the magic fixed number for cameras using the Four-Thirds lens system should be 21.64, rather than 50.

    What I'm wondering now is what I need to be able to change/increase the magnification. Is there some kind of Barlow lens meant to fit between the scope and the camera adapter?

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    Excuse me, I meant "Micro Four Thirds," not "Four Thirds." I hadn't realized there was a difference.

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    Default Re: Magnification with fixed camera body

    Very helpful discussion. Thanks folks!

    Steve

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    Default Re: Magnification with fixed camera body

    Quote Originally Posted by littlenemo View Post
    What I'm wondering now is what I need to be able to change/increase the magnification. Is there some kind of Barlow lens meant to fit between the scope and the camera adapter?
    I know this is an old thread, but I am wondering the same thing. Can someone please touch on this?

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    Default Re: Magnification with fixed camera body

    Quote Originally Posted by Mikester View Post
    I know this is an old thread, but I am wondering the same thing. Can someone please touch on this?
    In prime-focus configuration, the magnification is fixed based on the telescope's focal length and sensor diagonal size. The only means of altering this, in prime focus configuration is use of a focal-reducer. For SCT's, this is a fairly common practice, and the reducer fits in the rear-cell of the telescope. This is less common for Newtonian reflectors and refractors, but there are threaded reducer lenses that can be used with these telescopes.

    Using eyepiece-projection techniques it is possible to increase the focal length/magnification - there are adapters that allow the use of a limited number of eyepieces in the barrel of the adapter that re-image the eyepiece view onto the camera sensor. This configuration is more difficult in general to use, and requires more rigidity in the optical system, a very steady and rigid mount, and can difficult to obtain focus - it is typically used for planetary photography as an alternative to video-imaging based planetary AP.
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    Default Re: Magnification with fixed camera body

    Thanks for the info. So if I understood correctly, I can use a focal reducer/corrector to change my exit pupil at higher magnification for observing; but for photography, I am either bound by the ratio of the camera body-to-scope lens ratio, or I would need to mount a camera to an eyepiece vs. fix it to the OTA?

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    Default Re: Magnification with fixed camera body

    A question about the DSLR cal. I have a Canon 550d, sensor info. is 22.3 x14.9 and my scope is 1500mm FL. When I put the figures in the calculator it gave me 56x, My question is, is this the power at Prime Focus? Thanks in advance

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    Default Re: Magnification with fixed camera body

    Yes, it is the power in the prime focus
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    Default Re: Magnification with fixed camera body

    Or to be more precise, the chip will capture the same field of view as a 30mm eyepiece :-)

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    Default Re: Magnification with fixed camera body

    Here is a handy calculator.
    Calculator for DSLR Astrophotography
    Bill

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