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  1. #1
    Sunnycharlie's Avatar
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    Default Which ep is best?



    I am hoping to buy a 4.7mm ep for viewing planets and the moon with my new Orion XT8i - when it arrives. I was hoping to buy the Meade 5000 4.7mm uwa ep from the States and get it sent over here by my cousin. I am, however, having problems paying for things from the UK- I may get it sorted. I have come across the Explore Scientific 4.7mm 82° Series Eyepiece from another post in this forum and they are available at a reasonable price in the UK.
    So my question is which is better? And if one is better, then how much better? Will I notice a difference?

    Many thanks!

  2. #2
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    Default

    You will not noticed any different.
    Either one will work equally as well, when skies allow.
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  3. #3
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    Default

    A 4.7 mm eyepiece in your Orion XT8i eyepiece will give you 255x magnification. There are very few nights in a year where you can use this much magnifications because of seeing conditions.

    Instead, I would get a 2x barlow lens to double your magnification on the eyepieces that came with your telescope. This should give you as much magnification as you are likely to use.

    Then I would look at purchasing a 2" low power wide focal view eyepiece such as a 32 or 32mm for lovely wide views of the sky.

    Most of my higher magnification viewing on my XT8i is usually at 100x (10mm) to 120x (8mm). I almost never use the 4.9mm eyepiece I purchased.
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  4. #4
    Sunnycharlie's Avatar
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    Default

    Thankyou for that. I have already purchased a 2" 30mm wide angle ep and am looking forward to some spectacular viewing when my scope arrives.

    I know the 4.7mm ep is not for everyday(night?), but I wanted to buy a good quality high powered ep for the nights when I can use it. I do love looking at the moon and the planets.

    I have already had a discussion about barlows and whether they impair the view at all. It seemed to me that an ep is at its best without a barlow and that is why I wanted to buy a 4.7mm ep. I already have a selection of less good quality eps.

    I am still interested in any opinions on the 2 eps mentioned originally.

  5. #5
    Bob327's Avatar
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    Default

    While I agree that I personally would NOT buy any 4.7 mm eyepiece for you scope for the reasons others have already stated (lack of usability) I see not reason at all to buy a Ultra wide angle high powered eyepiece ...none at all.. !

    High powered views are for the moon and planets ...at 250-x that planet will still be the exact same size ..but will appear even smaller in a UWA eyepiece because the FOV is so much larger...the net effect on you brain is that the target is smaller...

    I also agree that your eyeballs will not be able to tell if you have a Barlow in a 9 mm eyepiece or you are using a 4.7 mm eyepiece by itself.

    For quality High Powered eyepieces I personally would look for either a Televue Radians or Pentax XF or XW's... If you want Good but not spend a lot of money the Baader Hyperions would be on my short list...

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  6. #6
    Sunnycharlie's Avatar
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    Default

    I think I'm getting confused now......

  7. #7
    MarkM's Avatar
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    Default

    Quote Originally Posted by Bob327 View Post
    While I agree that I personally would NOT buy any 4.7 mm eyepiece for you scope for the reasons others have already stated (lack of usability) I see not reason at all to buy a Ultra wide angle high powered eyepiece ...none at all.. !

    High powered views are for the moon and planets ...at 250-x that planet will still be the exact same size ..but will appear even smaller in a UWA eyepiece because the FOV is so much larger...the net effect on you brain is that the target is smaller...

    I also agree that your eyeballs will not be able to tell if you have a Barlow in a 9 mm eyepiece or you are using a 4.7 mm eyepiece by itself.

    For quality High Powered eyepieces I personally would look for either a Televue Radians or Pentax XF or XW's... If you want Good but not spend a lot of money the Baader Hyperions would be on my short list...

    Bob G
    Again, I disagree.

    I have used all sorts of FOV EP's and the image always appears the same size to me in an EP with the same mm FL. Never have I seen the phenomenon you describe.

    Bob, when is the last time you had to nudge a Dobsonian telescope to keep a planet at high magnification in view?

    Having to nudge a scope less often at high magnification for small objects (planets) is a huge plus to owning wide angle eyepieces. It is clear you are not fond of them, Bob; many others find them very useful. I would love to use Radians in my scopes--but the constant nudging due to the narrow FOV would negate my positive viewing experience--if I had tracking like you do--sure, bring on those eyepieces.

    With respect to use of a 4.7mm in an 8" reflector, I have used a similar EP (5mm) (240x) on my XT8i many, many, many, many, many times on Mars, Jupiter, Saturn, Uranus and Neptune and have gotten a very clear image--maybe my jet stream isnt as bad as others have it. But for my XT8i this was a little over half of the useful mag I can get from it. Often I would go to 340x or even 400x for additional details. And yes, higher magnification is also used on Deep Sky Objects depending on the situation--it is not only for the moon and planets. I have ample references where high magnification is used in reflectors for detecting structural details of these objects if anyone is interested.

    Regarding a Barlow--if you use an average Barlow with a high end eyepiece, you will get an average image. Your view will be reduced to the weakest link in the optical train. Sure you can get to 250x by adding a Barlowing a 9--but I would still go wide angle if you dont have tracking. I know in my Dob (because I have done the studies looking at the number of moons, colored bands, dark surface markings, etc.) that the view is NOT quite as good with or without the Barlow [I own a Celestro Ultima] using same quality eyepieces giving identical or similar magnifications. Would these results be the same if I owned an SCT--I dont know--which is why I would never feel comfortable giving advice to owners of these higher f number instruments.
    Location: 30° 19' N; 97° 54' W; elev 248 meters; yellow/green zone; NELM 5.7
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  9. #8
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    Default

    Thankyou, you have reassured me that I am doing the right thing. I trust your advice as you have the same scope that I will have.

    I think I will wait a while anyway, enjoy the eyepieces I have and look around for a good offer somewhere. There is no rush!!

    I am still interested in any comments on the 2 eyepieces I originally asked about.... I read a review somewhere that the Meade is better in a faster scope- did I get that right? I must admit to not knowing quite what that means or whether it is important....

  10. #9
    MarkM's Avatar
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    Quote Originally Posted by Sunnycharlie View Post
    Thankyou, you have reassured me that I am doing the right thing. I trust your advice as you have the same scope that I will have.

    I think I will wait a while anyway, enjoy the eyepieces I have and look around for a good offer somewhere. There is no rush!!

    I am still interested in any comments on the 2 eyepieces I originally asked about.... I read a review somewhere that the Meade is better in a faster scope- did I get that right? I must admit to not knowing quite what that means or whether it is important....
    That is a good plan. Hard to tell at this stage if your atmosphere will support higher mag views--it may or may not, but you will find out. Also---see if you can borrow eyepieces from someone to get more data.

    A "fast scope" refers to the f number; there is no definite cutoff, but most folks would say a f/5 scope is reasonably fast and f/10 is slow. In general, dobs occupy the realm of the "fast", whilst SCT's and refractors are "slow".

    The faster scopes tend to require slightly better quality eyepieces. Your XT8i is f/5.9---so it is kind of in between--this mean it is really handy as a dual purpose instrument because planets do well with slower scopes and deep sky objects are best with as much mirror as you can throw at them (which can often be accomplished most economically with a reflector)
    Location: 30° 19' N; 97° 54' W; elev 248 meters; yellow/green zone; NELM 5.7
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