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Thread: How to focus

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    Default How to focus



    So guys, i have similar questions to the above, my question is, if you take the lens off camera, and set the camera up with a t2 adapter etc, exactly how do you focus on the image in the scope? do you use the telescope focuser? ie the barlow lens or whatever you have connected to the scope? and as you adjust the focuser, it moves the camera in or out to the scope?
    Obviously a newbie to this, but have the basic idea!

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    Default Re: How to focus

    This has been shifted so doesn't make much sense now....

    What i'm trying to work out is, when mounting a camera to a telescope, and using a T2 adaptor, which requires removing the cameras lens, how do you then focus the camera? As you wind the scope eyepiece in or out, does that focus the image to the camera?
    thanks for your help in advance!

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    Default Re: How to focus

    This is called prime focus photography and the telescope becomes the lens and you focus with the telescope focuser. Think of it this way, my telescope has a focal ratio of f/4 and a focal length of 1000 mm. When I attach my camera I am shooting through a 1000 mm telephoto lens with a focal ratio of f/4.
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    Default

    When you use a t adapter, you connect the camera to your scope and then focus with the telescope the same way you would focus if you were using an eye piece. The telescope becomes the lens. It sounds like you have the right idea.
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    Default Re: How to focus

    In my experience, the camera focuses in a different place from the eyepiece. I generally can't see the object I'm shooting in either live view or the viewfinder. This is my procedure, and if someone can improve on it, please let me know.
    First, I find the brightest star in the area where i'm shooting, put on the Bahtinov mask, and take pictures of the star. I move the telescope focus back and forth until the diffraction spikes on the image appear right. A 30 or 40 second exposure seems to work. After I get the right diffraction spikes, I slew back to the the object I'm shooting, hope for the best, and fire away. Attached is my best result, so far.M51.jpg
    So far, that is the best I can do.
    Kazakonyi, I hope this helps a little.
    Bob (rhb007)
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    Default Re: How to focus

    Thanks so much for your reply's guys, i have trawled through a heap of previous posts about this and and have got the idea, (some pretty confusing posts some of them....,), and found a U tube vid ( Attaching an SLR camera to your Newtonian Telescope - YouTube) Thanks rohitud, that explained it simply!
    Now to get the T thread and have a go, i have since worked out the live view through laptop (how interesting!)
    rhb007: nice shot!

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    Default Re: How to focus

    hi guys, newbie back again!
    So, i have a variable projection eyepiece camera adapter, i have fitted my Canon to the T piece end, the other to the scope (skywatcher 114/900), I am using a 20mm eye piece (the largest i have), and i can see the view via the "Live view" on the camera, but it is too magnified, ie I can only see half the moon, not all of it, i have tried the variable projection at the closest position (which gives the largest FOV), and of course at the furthest point it is a smaller FOV, so my question: what size eye piece do i require to get to photograph all of the moon? 30mm?
    I tried this variable projection piece as a prime focus set up, but that requires the camera to be really close to the scope, and i can't get it close enough, (i did physically hold the camera up to the scope and got some pictures like that, but not really a satisfactory way of doing things!)
    So not sure where to go now, a barlow lens set up with camera adapter fitted?
    Thanks for your replies in advance!
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