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  1. #1
    ddfurlow1s's Avatar
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    Default low mag for xt10



    hey guys i was just running the numbers for mag on the 1200 focal length xt10, it seems that a 25mm ep would give me a magnification of 48x
    i most likely wouldn't need anything lower than that would i?
    what i am wondering is, would a ep at this mag with a fov of 70 capture the entire view of most extended objects?
    thanks guys

  2. #2
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    Default

    Quote Originally Posted by ddfurlow1s View Post
    hey guys i was just running the numbers for mag on the 1200 focal length xt10, it seems that a 25mm ep would give me a magnification of 48x
    i most likely wouldn't need anything lower than that would i?
    what i am wondering is, would a ep at this mag with a fov of 70 capture the entire view of most extended objects?
    thanks guys
    My lowest power combination is 42X. Nice for the Double Cluster and Pleiades.

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    Orion XT12i Intelliscope on a Tom Osypowski Equatorial Platform
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  3. #3
    Canon Pete's Avatar
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    Default

    The math is right. Probs be as low as you would want to go.

    Clear Skies

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  4. #4
    ddfurlow1s's Avatar
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    i;m really glad you replied, i like your setup, i think i'm gonna go for the laser/finder scope using the dual finder method you are using, i'm also thinking i'll get a telrad for the winter months
    i was wondering how you like those q70s in your xt10 and if they are the same as the agena astro just rebranded

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    My lowest power for my XT10i is 34x with my 35mm Panoptic. That gives me a 1.84 degree field of view and its great for those large open clusters and nebula.
    Adlartok...Chris

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    Default

    Quote Originally Posted by ddfurlow1s View Post
    hey guys i was just running the numbers for mag on the 1200 focal length xt10, it seems that a 25mm ep would give me a magnification of 48x
    i most likely wouldn't need anything lower than that would i?
    what i am wondering is, would a ep at this mag with a fov of 70 capture the entire view of most extended objects?
    thanks guys
    If you're young you might go to 35x, but if you are my age 48x is the best you can do.

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    Default

    My lowest magnification is 30x, in my Pan27. The view is gorgeous! I can almost get all of M31 into it, on the rare nights when it is dark enough to see most of it.

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  8. #8
    reborn's Avatar
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    Question

    Quote Originally Posted by kencrowder View Post
    If you're young you might go to 35x, but if you are my age 48x is the best you can do.
    why is that? I understand the exit pupil would not be optimal but is there another reason you wouldnt want lower power? My 35panoptic gives an exit pupil above 7mm but the extra FOV it provides is beautiful.
    Adlartok...Chris

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    kencrowder's Avatar
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    Default

    Quote Originally Posted by reborn View Post
    why is that? I understand the exit pupil would not be optimal but is there another reason you wouldnt want lower power? My 35panoptic gives an exit pupil above 7mm but the extra FOV it provides is beautiful.
    When the exit pupil is larger than the eye iris, you have lost the effect of your aperture. That's the only reason I know of. For example, at 25x and a 5 mm iris you have a 125 mm equivalent scope even if the physical dimension is 12 inches.

    I like the math, so for others like me the limit is when the aperture divided by the iris is equal to the magnification. The magnification is equal to the aperture times the f/no (scope fl) divided by the ep fl. Thus you may see the rule that the ep fl should be less than the iris times the f/no.

    I find it interesting that it depends only on F/no. The aperture drops out of both sides.

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  11. #10
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    My lowest mag in my XT10i is x42 with my Skywatcher Nirvana 28mm, with it's 82 degree AFOV it delivers 1.9 degrees TFOV and an exit pupil of 5.9mm

 

 
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