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  1. #1
    mtenergy1's Avatar
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    Default Zhumell Z series Planetary 3mm Eyepiece



    A couple days ago was my first look ever through a telescope so I'm not sure what to expect and would like to get some opinions.

    I purchased the celestron astromaster 130 EQ with a zhumell z series plantary 3mm eyepiece. So far I've only done terrestrial viewing & have to say I've been disappointed with the zhumell 3 mm eyepiece. The 20 mm EP that came stock with the scope I was amazed with. The image from far off in the distance was close, crystal clear, colorful & sharp. The 10 mm stock EP I was even more amazed with because the quality of the image was just as good & closer. Couldn't wait to put in the higher quality zhumell EP in & get really close. What a let down. The quality was severally reduced. The image was grayish almost grainy, color & contrast was severally reduced, image wasn't as sharp no matter how I tried to focus it. Spent the next couple hours researching and came across an article that pretty much had the same problem I was having & it was caused by viewing it through a window. Was able to sleep well after that & assumed that was my problem. Today I was able to take the telescope outside & again zoomed in on the same terrestrial image. There was absolutely no difference from when I was viewing it through the window & when I was not.

    Am I expecting to much? Is this normal for this type of lens? Every review I came across for this lens was saying that they compare to lenses that cost 3-4 times as much. Heres what one person said, "I compared the Zhummels to a TV Radian and while the Radian was better it wasn't 4 times better".

    On telescopes.com it says the highest useful magnification for the telescope is 150. I thought this was a typo considering it has a 130 mm aperture. Could it be because I have gone past the highest useful mag for this scope? It's has a 650 mm focal length so my 3 mm EP is giving me 216x. Do you think there's something wrong with the EP itself? Maybe the telescope? Or like I said before am I expecting to much? I'm a little worried because when I finally point it to the heavens I don't want to have the 3 mm EP become a $50 paperweight.

  2. #2
    jenniferchristine's Avatar
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    Default

    The problem with going over 200x terrestrially is that you're peering through mud (also called atmosphere) every particle for the next 50 kilometres is part of your scene - every dropelet of water every tinypiece of smog soot and dust. Not only that, you've also picked up all the turbulence and heat shimmer
    It's grey- Even a big fancy scope is grey!
    200x is very much a limit - my 8" was compared with a 4 inch just last week and I have to say, the 4" looked BETTER!
    It's a big ask even if you look at the sky, 200 is not always going to be clean and clear - but then an 8" is better than a 4"!
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  3. #3
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    Default

    You have also run into the diffraction limit. It starts when the magnificaton equals the aperture (130x for you). The eye resolution allows it to be larger before the details are no longer improving. That happens at about 1.5x the aperture or 200x for you.

  4. #4
    mtenergy1's Avatar
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    Default

    Thanks for the replies. The both of you have been very helpful. This might be a completely stupid question but will it be different when I'm looking into space, say Jupiter? Basically I want Jupiter to be as big as I can possible get it for my size telescope while still being able to see as much detail as possible. I don't know if I'm getting my hopes up with the telescope that I have but I would love to see some cloud bands & of course the GRS.

    Based on the diffraction limit for my scope which I don't fully understand but trust your judgement would anybody recommend that I return the 3mm in exchange for maybe a 5 mm lens giving me 130x?

  5. #5
    neal_mlc's Avatar
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    Default

    I would stick with your 10mm and get a Barlow instead. The barlow will allow you to have a 5mm with the eye relief of a 10mm. Also a Barlow will double your collection of EPs without have to buy the EPs.
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  6. #6
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    Maybe thats why its called a planetary EP and not a terrestrial EP. But yes, it should be better when used appropriately on planets. As long as your scope and seeing conditions permit.
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  7. #7
    kencrowder's Avatar
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    Default

    Quote Originally Posted by neal_mlc View Post
    I would stick with your 10mm and get a Barlow instead. The barlow will allow you to have a 5mm with the eye relief of a 10mm. Also a Barlow will double your collection of EPs without have to buy the EPs.
    I agree. This is a better choice than a 5 mm plossl ep.

  8. #8
    Philip F's Avatar
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    Default

    The Zhummell Z-series is a clone of the Orion Edge-on lanatey eyepieces which I love. Great eye releif, clear wide flield of view. The earlier answers hit the reason for the disappointing reslts your getting on the head.

    However, for general reference you can use the focal ratio of the scope to define your lowest focal length of useable eyepiece. The faster the scope the more eyepiece mag it can handle. I have a 6mm Orion edge-on for my f5 scope because only the best nights would it be able to handle a 5mm. I put my 14. edge-on in a 3x barlow for those clearest of nights to take the magnification to the limit. I would sell or trade the 3mm to someone with an unltra-fast scope.

    Since our scopes have identical apetures, focal lengths and thus f-rations, you should have the same eyepeice limitations.

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  9. #9
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    Default

    Quote Originally Posted by kencrowder View Post
    I agree. This is a better choice than a 5 mm plossl ep.
    In agreement here too. I have used 236x, but my best viewing comes a lower powers, which means more detail. Your 10mm barlowed will give you lots of usable power.
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  10. #10
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    Default

    More magnification causes the image to get dimmer and fuzzier, once you go beyond a certain point. Sure, the object may appear bigger/closer to you, but you will actually see a lot less detail than at a lower, more reasonable magnification. The only object that I've ever looked at with that much magnification is the moon, and even then I backed down to a more reasonable power soon afterwards. I would not expect a 130mm scope to give decent views beyond 150X-180X for most objects. It has a lot to do with the atmospheric conditions and the quality of the scope's optics too.
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