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Thread: eyepieces

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    jamesdmc28's Avatar
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    Default eyepieces



    need help urgently,

    I need better eyepieces than the ones supplied with a Jessops TA 1000-120 refletor scope, any ideas would be greatly appreciated!!
    Makes, Models and Prices Please, or where to look!! thanks

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    Default

    Hi James.

    Read the 'stickies' on top of this section:
    Telescope Eyepieces Forum - Astronomy Forums | Telescope Forums & Reviews | Astronomy Community

    After that, do your research and, of course, ask the forum again !

    Hope it helps

    Scope:
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    Default

    Hi James,
    First of all, what eyepieces do you have?

    Any telescope has an upper magnification limit of around 2x per mm of aperture - Imagine a digital picture.... you can zoom in so far, and eventually you'll see the pixels that make up the image - if you zoom in further, the pixels will get bigger, but you won't see any more detail.
    It's a bit like that with telescopes - once you reach that 2x per mm, you can continue to rack up the power, but you'll see no more detail.
    The image WILL get bigger, but will get more and more indistinct and blurry - all you do is accentuate any optical shortcomings in the telescope, or the atmospherics.
    I nice sharp image of Jupiter at 120x, will become an indistinct fuzzy mess at 400x

    With 102mm of aperture, the best you can expect is about 200x under ideal conditions.
    Unfortunately, we never get ideal conditions, and no telescope is optically perfect.
    Atmospherics change all the time, after all, we are looking through something like 50 miles of constantly-moving air if you're looking upwards, or possibly hundreds of miles of air if looking at an object low down near the horizon.
    It's rare that you'll get a good, sharp, image when you're near your scope's limit.

    Your telescope is a budget-range model, with a relatively long focal ratio - which points to your main mirror being of spherical figure.
    Spherical mirrors in small-ish newtonians, sadly aren't really capable of much beyond 100x, maybe 120x, before the image starts to break down (becomes 'fuzzy' and indistinct, no matter what eyepiece you use)

    Don't lose heart though - you have enough aperture to see many, many objects in the sky - Charles Messier created his list of deep-sky objects with telescopes of around 100mm aperture most of the time.
    And 100x-120x is plenty enough magnification for most observing - just bear in mind that you won't see much detail in very small objects, such as Mars.
    Some small star clusters also benefit from some extra magnification, very tight double-stars, and it's nice to 'float' across the Moon at high powers.
    Other than that, most of us don't use high magnifications all that often.

    I regularly use 8" and 10" scopes - and it's rare I go much beyond 150x - I do the VAST majority of my observing between 50x and 120x

    Your scope has 1000mm focal length, so I wouldn't go shorter than an 8mm eyepiece (125x) or maybe 7mm (143x) - and I'd only use one of those on the steadiest nights.
    I wouldn't bother barlowing any eyepieces shorter than about 15mm either - but a barlow may be useful to get alternative powers from, say a 25mm, or 20mm
    If you do decide to get extra eyepieces, go for better ones, rather than more powerful ones.
    Speaking from experience - as you continue in the hobby - scopes come and go, but you tend to hang onto good eyepieces long-term.
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  4. The Following 4 Users Say Thank You to Carlos_dfc For This Useful Post:

    JAHamm (01-16-2012),jamesdmc28 (01-16-2012),JuanM (01-19-2012),smcclenaghan (01-16-2012)

 

 

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