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  1. #1
    brian's Avatar
    brian Guest

    Default eyepiece advice..

    Ok, here's my question:

    I have an 8 inch newt on a german eq mount. I have a nice televue
    panoptic for looking at deep sky stuff and a celestron xcel for
    planetary viewing. Of course i've gotten used to the superior optics of
    the televue so I want to get another for the planets. I've made a few
    calls to the local telescope shop and the guy tells me that I want a
    televue nagler type 6 at 3.5 or 5mm. They're both the same price and he
    wasn't real clear on the difference so I'm hoping the fine folks on this
    bb can pass on any advice in this area. So, which piece do you think is
    best? Or is there something more awesome than the vaunted Televue line?
    Money is no object so if there's some kind of ultra sophisticated
    eyepiece crafted by japanese hermits in a secrete underground laboratory
    ....I wanna know.
    Thanking you in advance for your expert advice,


  2. #2
    Odysseus's Avatar
    Odysseus Guest

    Default eyepiece advice..

    brian wrote:

    How short an eyepiece you can use depends on the focal length of your
    primary. The usual rule of thumb says that you won't benefit from a
    magnification greater than 50X per inch of aperture, so your limit
    will be about 400X. If your mirror's focus is shorter than 400 * 3.5
    mm = 1400 mm (meaning that the 'scope is faster than about f/7), the
    3.5-mm EP should let you make the most of good seeing conditions, but
    if it's longer (slower) than that the 5-mm EP would be a better choice.




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