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  1. #1
    armor's Avatar
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    Post wanted to know your opinion on a eyepiece



    hi friends

    wanted to know your opinion on a eyepiece,I have one (Celestron Astromaster 114eq and I want to buy one of these two eyepiece:

    X-Cel Series 1.25 in - 2.3mm

    X-Cel Series 1.25 in - 5mm

    which is best?

  2. #2
    Bob327's Avatar
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    Need the Focal Length of the scope to give you any "honest" answer...

    Both eyepieces are of the same design by the same manufacturer so the eye relief etc should be very similar....

    In my Celestron 114 GT (a Newt vwith a FL of 1000) the 2.3 mm would yield 434x and the 5 mm would yield 200x....

    The 2.3 mm Would be too much magnification for MY scope to handle even under absolutely positively PERFECT seeing conditions.. the 5 mm MAY be able to be used one or two nights every 2 or 3 years ...

    In General 50x per inch is the Maximum you can get the scope to be able to handle ...so 4.5" x 50x means IN THEORY you will be able to use up to 225x..

    Bob G.
    CPC1100 housed in a slotted domed observatory (Exploradome) 4 and 5 inch refractors for use from the lawn, a 8" Sct (NS 8i) for star parties...
    I Hate the winter so I use heated Motorcycle clothing to stay warm while observing in winter
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  4. #3
    Inkie's Avatar
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    I purchased a large, very nice Meade 8.8mm Super Plossle before I took delivery of my 11" Celestron. I have had few good views with that combination, and can't say I have had any excellent ones. So, on the basis of probability, if my 15 years of using telescopes counts, you are highly unlikely to have any comforting use of the 2.5mm eyepiece, or of the notion that it was a wise investment. I wouldn't bet much on the larger one either.

    For the scope you are using, even if the optics are exceptional, you would almost never enjoy magnifications greater than about 200X. The reason is that the skies above you will almost always be the great determinant of good viewing. When you push a scope close in magnification to the diameter of the primary optical light path, you quickly experience diminishing returns.

    -Crandell

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  6. #4
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    Arrow

    then, could be the best option the X-Cel Series 1.25 in - 8mm



    thanks for you time

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    Quote Originally Posted by armor View Post
    then, could be the best option the X-Cel Series 1.25 in - 8mm



    thanks for you time
    Hi Armor ..First of all , Welcome to the forums ...I started out with a scope simular to yours in the meade brand .... 114/1000mm and the highest power my scope could handle was about 200 power .... It also depends on what you like viewing ? Nebula's/galaxys , planets/moon , or constelations and cluster's ...And what other eyepieces and barlows you already have ....
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  9. #6
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    Quote Originally Posted by roverich View Post
    Hi Armor ..First of all , Welcome to the forums ...I started out with a scope simular to yours in the meade brand .... 114/1000mm and the highest power my scope could handle was about 200 power .... It also depends on what you like viewing ? Nebula's/galaxys , planets/moon , or constelations and cluster's ...And what other eyepieces and barlows you already have ....

    hello roverich, Inkie, Bob327 and everyone.... I like to see all Nebula's. Galaxys, planets / moon .... I have one of two eyepieces 20mm and 10mm, but I like to see with my telescope, the rings of Saturn, or galaxies, clusters of stars, make the most of my telescope, I have the opportunity to buy one of these eyepieces for this purpose, but as you have experience like me to help me make a good decision

    A better option would be...

    Celestron 2x Omni Barlow:

    Meade 6.4mm 1.25" Plossl Eyepiece
    Celestron 6mm High Power 1.25 Plossl
    Celestron 9mm 1.25" Omni Plossl

    or Celestron 8mm X-Cel Long Eye Relief Telescope Eyepiece

    which could be the best combination?

    really thank you very much for your time, I have an existential problem ..


  10. #7
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    Maybe the right way to go about this decision is to decide what you want your scope to do for you. Keeping in mind its light-gathering power, its focal length, and the quality of the optical system, I hope you understand that textbook images of Jupiter and galaxies is definitely an unrealistic expectation. Perhaps in truly exceptional seeing, if the mirrors are really well collimated, plus cooled, and the Gods smile on you, you could anticipate some breathtaking images with a CCD if you were to stack them with expensive software. But your Mark I Eyeball and so-so seeing with a mirror that is well cooled and still not fogging up on you, will give you 'normal' views that such systems should deliver, and that mortals should anticipate.

    Two of us have opined that about 200 power is the most you should ask of your scope. What would you want to examine at that magnification? I suspect that the Moon and any of the visible planets are about the most one should should think of at that magnification. Even exceptional comets won't look great at that magnification. For faint fuzzies, extended objects (Andromeda, for example), you would want about 20-50 power at most. Chances are you have such an eyepiece already.

    I take it that you know how to compute the magnification that an optical system renders with a given ocular focal length? Take the focal length of the prime mirror and divide that by the focal length of the ocular you intend to use. The resulting figure is your magnification. Altering the formula, you can figure out what eyepiece focal length will give you the maximum useful magnification for you telescope...we agree on 200? (Please nod.) So, if you were to divide the focal length of your scope by 200, you will get the focal length of the ocular you need for the magnification. Plug in the figures and look for an ocular that you don't already have. For a focal length of 1200m, you get a 6 mm eyepiece.

    I can't end this post without reiterating that you will very likely not enjoy much use out of that eyepiece. Once you have tried it a few times, you will almost never get it out of its protective cover. That is what happened to my very costly Super Plossel from Meade.

    To put this into perspective, I have an 11" SCT with good optics...not great optics, just good optics. 90% of my viewing over 15 years has been with 17mm and a 32 mm eypieces. For specatacular wide viewing of galaxies and clusters, I have a 60mm Ultima eyepiece from Celestron. Its exit pupil is now too large in diameter for my aging eyes to use fully. I would now be better to use a 45mm eyepiece, maybe a 50 mm. For my 11" scope, with a 2800 mm focal length, the most powerful ocular is the 17 mm, as you would anticipate, and it yields only 164 power. With that magnification and the smaller field of view, the inner Orion Nebula is very pretty, but I only see a very little of the grander view the nebula offers. Saturn, on the other hand, is quite spectacular. When I convince myself that I have a really good night of seeing, I have switched to the 8.8 mm and been disappointed more times than I can say.

    I'm just trying to provide you with some guidance, and hoping to spare you some dollars and disappointment. I would guess that an eyepiece near 8-10 mm would be about the most you can expect your scope to agree to work for you.

    -Crandell
    Last edited by Inkie; 12-22-2009 at 05:57 AM.

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  12. #8
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    Quote Originally Posted by Inkie View Post
    Maybe the right way to go about this decision is to decide what you want your scope to do for you. Keeping in mind its light-gathering power, its focal length, and the quality of the optical system, I hope you understand that textbook images of Jupiter and galaxies is definitely an unrealistic expectation. Perhaps in truly exceptional seeing, if the mirrors are really well collimated, plus cooled, and the Gods smile on you, you could anticipate some breathtaking images with a CCD if you were to stack them with expensive software. But your Mark I Eyeball and so-so seeing with a mirror that is well cooled and still not fogging up on you, will give you 'normal' views that such systems should deliver, and that mortals should anticipate.

    Two of us have opined that about 200 power is the most you should ask of your scope. What would you want to examine at that magnification? I suspect that the Moon and any of the visible planets are about the most one should should think of at that magnification. Even exceptional comets won't look great at that magnification. For faint fuzzies, extended objects (Andromeda, for example), you would want about 20-50 power at most. Chances are you have such an eyepiece already.

    I take it that you know how to compute the magnification that an optical system renders with a given ocular focal length? Take the focal length of the prime mirror and divide that by the focal length of the ocular you intend to use. The resulting figure is your magnification. Altering the formula, you can figure out what eyepiece focal length will give you the maximum useful magnification for you telescope...we agree on 200? (Please nod.) So, if you were to divide the focal length of your scope by 200, you will get the focal length of the ocular you need for the magnification. Plug in the figures and look for an ocular that you don't already have. For a focal length of 1200m, you get a 6 mm eyepiece.

    I can't end this post without reiterating that you will very likely not enjoy much use out of that eyepiece. Once you have tried it a few times, you will almost never get it out of its protective cover. That is what happened to my very costly Super Plossel from Meade.

    To put this into perspective, I have an 11" SCT with good optics...not great optics, just good optics. 90% of my viewing over 15 years has been with 17mm and a 32 mm eypieces. For specatacular wide viewing of galaxies and clusters, I have a 60mm Ultima eyepiece from Celestron. Its exit pupil is now too large in diameter for my aging eyes to use fully. I would now be better to use a 45mm eyepiece, maybe a 50 mm. For my 11" scope, with a 2800 mm focal length, the most powerful ocular is the 17 mm, as you would anticipate, and it yields only 164 power. With that magnification and the smaller field of view, the inner Orion Nebula is very pretty, but I only see a very little of the grander view the nebula offers. Saturn, on the other hand, is quite spectacular. When I convince myself that I have a really good night of seeing, I have switched to the 8.8 mm and been disappointed more times than I can say.

    I'm just trying to provide you with some guidance, and hoping to spare you some dollars and disappointment. I would guess that an eyepiece near 8-10 mm would be about the most you can expect your scope to agree to work for you.

    -Crandell
    ohhh, thank you very much, I have been very helpful in making this decision, thanks Inkie,roverich and Bob327....... is the first forum I go I respond so quickly, and so seriously, I am eternally happy, thanks to everyone

    happen to have pictures of their telescopes?

  13. #9
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    Crandell's (aka Inkie) reply would make a great sticky in the eye-piece section, I think! As a new scope owner, I am trying to overcome the urge to buy accessories before I have fully learned to use what I have. This is another post that has really helped me put things into perspective. Thanks Crandell!
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    Another item to consider is comfort. I've never owned an ep in the X-cel line, so take this info as second hand, but many people who do own these either love them or hate them. It seems that eye position is tricky with this series. If your eye isn't just in the right spot the eyepiece suffers from blackouts and kidney beaning (think kidney bean shaped black out).

    Just something to consider in addition to the other great advice you've been given...
    Craig

 

 
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