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Thread: How to know which reflectors will reach focus for AP

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    Default How to know which reflectors will reach focus for AP



    As the title states I'm considering a reflector for viewing and AP and was wondering how to tell which ones will reach focus with a DSLR in the eyepiece?

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    Default Re: How to know which reflectors will reach focus for AP

    Ones that are labeled as astrographs will achieve focus...
    Most ordinary reflectors, will not.
    You would have to either move the primary mirror up in the tube, or use a barlow to bring the focus point inwards.
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    Default Re: How to know which reflectors will reach focus for AP

    Quote Originally Posted by jimminCT View Post
    Ones that are labeled as astrographs will achieve focus...
    Most ordinary reflectors, will not.
    You would have to either move the primary mirror up in the tube, or use a barlow to bring the focus point inwards.
    So in that case does that mean that every reflector can reach prime focus then with a Barlow or are there still odd ones that don't?

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    Default Re: How to know which reflectors will reach focus for AP

    Quote Originally Posted by Sean90 View Post
    So in that case does that mean that every reflector can reach prime focus then with a Barlow or are there still odd ones that don't?
    Most will... but at the expense of FoV.
    There's always a trade off in this game...

    **edit**
    I know enough to NEVER say never, or always... 'cause that ain't how life works...
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    Default Re: How to know which reflectors will reach focus for AP

    Quote Originally Posted by jimminCT View Post
    Most will... but at the expense of FoV.
    There's always a trade off in this game...

    **edit**
    I know enough to NEVER say never, or always... 'cause that ain't how life works...
    Thank you very much for the information

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    Default Re: How to know which reflectors will reach focus for AP

    Are you needing a mount to go with it? If all you need is the OTA, take a look at the offerings from GSO in their F/5 line. They look to get good solid reviews, with optics set for astrophotography, and, include an extension tube for visual. They also come with mounting rings, finder, and dovetail bars, all at a VERY reasonable price. I've been eyeballing the 6" f/5 myself.

    https://agenaastro.com/telescopes/te...hopby/gso.html
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    Default Re: How to know which reflectors will reach focus for AP

    Using a barlow for visual with a standard reflector is less than ideal. It increases the focal length, increases the f-ratio, narrows the field of view, inserts more pieces of glass in the optical train which can create distortions.
    With an astrograph you may have the opposite problem in that the focuser my not come out far enough to reach focus for visual use. This is easily remedied by using an extension tube.

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    Default Re: How to know which reflectors will reach focus for AP

    I personally wouldn't consider a reflector for AP. A nice refractor would be ideal for AP. Even the reflectors that are astro graphs aren't gonna give you the same shots as a refractor. I just use a reflector for visual, but that's me.
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    Default Re: How to know which reflectors will reach focus for AP

    Do NOT use a Barlow because it will make your scope much slower. Get an astrograph, they are quite affordable and can yield great images when used with a coma corrector (see geethq, Kathy, … many examples of how well Newts can perform).

    Personally I recommend a Mak-Newt, they don't require a coma corrector and give a very flat field. The Comet Hunter is my 6" Apo... works for visual and AP.

    Keep in mind you will need to use extension rings because the focal plane needs to be inside the eyepiece for visual and way outside of it for AP.
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    Default Re: How to know which reflectors will reach focus for AP

    First light optics sell the P-DS tange of scopes.
    The 130/150 and 200PDS.

    All very affordable and they focus a DSLR, visually they work well and I have no complaints with my 130PDS, it comes with all the bits and pieces that make it a simple case of attaching the camera without having to purchase additional adapters.


    First light optics-reflectors.

    In the link look for the 130/150/200 P-DS!
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