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Looking at your specs, Beardy and in light of the other telescope thread, my advice would be to play around with your scope for a few sessions before buying any new eyepiece. Get a feel for what your scope can do, the kind of things you like looking at and what magnifications you think would not only suit those objects best but also your own atmospheric conditions and light pollution content.

Other than that, I feel a basic set up of three eyepieces and a barlow (if you like using such tools) would tide things over for a while. Looking at what I mainly use with the 10" for DSO viewing (as opposed to planetary and Lunar) something around the following magnifications (or exit pupil) would be of some help:

Low-power, widefield, something around 40x.

Low mid-power, something around 90x.

High mid-power, someting around 125x

Thus, with the Barlow you'd have 40x/80x, 90x/180x, 125x/250x.

It's no way perfect but you get an idea of useful range. For planetary and Lunar work I find a run of eyepieces necessary which can offer maagnifictions of  about 15% increases from 140x upwards to about 250x for exceptional nights of seeing.

If you were into solar viewing (which one must never do naked eye) a useful bit of kit would be Baader's Solar Film and a magnification around 50x.

Keep on asking questions here and if you hang on for just a few observation sessions when you get your 8", I think you'll be able to make a much more informed enquiry and decision. It'll also give you time to look around the secondhand market and see what kind of things are on offer and at what price.

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There are a huge range of eyepieces available and with a huge range of prices attached too - anything from around £30 each to £500+ each !

This article is worth a read if you have not already seen it:

http://stargazerslounge.com/topic/43171-eyepieces-the-very-least-you-need/

Here is another good piece by a member of this forum:

http://www.swindonstargazers.com/beginners/eyepieces.htm

In one sense the choice will be steered by what you wish to spend on them which sounds odd but will help narrow down the choice a bit.

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Beardy30..........as a general rule use your Aperture size to determine what effectively your maximum magnification should be for practical reasons. Therefore Aperture 200mm = 200x magnification, for your Highest magnification eyepiece (low focal number )  use the focal ratio ( f/6)  as a guide  so lets  say 6mm EP.  The focal Length of the Skyliner 200P/D is  1200mm . Divided, 1200mm/6mm 200x magnification. ( I personaly chose an 8mm lens for 150x magnification. I will buy a 12mm next to get my 6mm, if that confuses you?)  For your lowest magnification lens (longest focal length - wider view) divide your Aperture by an exit pupil size of 7mm  ( but maybe 4-6mm depending on your age?) so 200/7= 28x magnification. That would give you an eyepiece size of about 42mm which is pushing the boundaries of the 1.25" barrel limit for wide views , but fortunately, you can use the larger 2" barrels. That choice is yours. As for eyepieces, it seems that higher prices bring better optical quality and construction. Im investing in the BST Starguider ED lenses and will soon have the 12mm 25mm and a 2xBarlow. Already have the 8mm 60` eyepiece and happy with it.

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Beardy30..........as a general rule use your Aperture size to determine what effectively your maximum magnification should be for practical reasons. Therefore Aperture 200mm = 200x magnification, for your Highest magnification eyepiece (low focal number )  use the focal ratio ( f/6)  as a guide  so lets  say 6mm EP.  The focal Length of the Skyliner 200P/D is  1200mm . Divided, 1200mm/6mm 200x magnification. ( I personaly chose an 8mm lens for 150x magnification. I will buy a 12mm next to get my 6mm, if that confuses you?)  For your lowest magnification lens (longest focal length - wider view) divide your Aperture by an exit pupil size of 7mm  ( but maybe 4-6mm depending on your age?) so 200/7= 28x magnification. That would give you an eyepiece size of about 42mm which is pushing the boundaries of the 1.25" barrel limit for wide views , but fortunately, you can use the larger 2" barrels. That choice is yours. As for eyepieces, it seems that higher prices bring better optical quality and construction. Im investing in the BST Starguider ED lenses and will soon have the 12mm 25mm and a 2xBarlow. Already have the 8mm 60` eyepiece and happy with it.

I am sorry but I disagree with a little of what you said your maximum theoretical mag is 50x per inch or 2xmm apparture which gives a theoretical 400x possible magnification. The seeing will limit the maximumum useful  magnification which on average limits it to 150-200x mag. 250x mag on a good day and more on those very good days

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I agree - 200x - 250x are the practical maximum useful magnifications for an 8" scope generally. You might get an occasion now and then when 300x can be used on a tight binary star though but really not often.

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rowan46..........dont be sorry.......your right, maximum theoretical magnification can be based on 50x per Inch of aperture. Its the standard figure (rule -of-thumb / general guidline) number that sits  between 40 - 60 which is whats normaly quoted over the www (but optimally, half those numbers would be more suitable/practical) for  technical reasons,  and your also correct that `seeing conditions`  reduce the telescopes theoretical ability, again due to technical reasons.

But i never gave  theoretical answers to beardy30, my  reply was based on  effective (practical) reasons. i did say ...."what effectively your maximum magnification should be for practical reasons"

But now i must apologize to beardy30, for not actually reading his question properly?

beardy30 asked for "Any Top Quality EP"  well I would say Tele Vue`s Delos, Nagler &  Ethos are good top quality eyepieces, about the best you can buy actually, but maybe an overkill for the 200P. My choice is the BST Starguiders.

 
So having mis-read the original question, but now answered,  my general guide  (which is not my own own made up  guide, its from information gleaned from here and the web)   funnily enough,  work reasonably well. take care

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beardy30.....All telescopes have their extremes, limits and practical useage. I think its safer to work within the practical use range, right from the start, rather than wasting time/money  in `trying` to achieve, what`s theoretically possible, but practically impossible, due the the technical issues that surround telescopes and astronomy.  How we interpret issues, guidelines & technicalities, is all part of the fun of learning, and why therefore, these forums exist. I digress, we should be talking about your  EP brands, sorry.

Check out  BST` Starguiders, TMB`s, ES(Explore Scientific) all good value.

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James - I understand from your post you have (or will be getting) a 200P dob. If you state a budget for your eyepieces then it will be much easier to suggest some brands and sizes that you will find useful.

E.g. do you want to get 5 eyepieces totaling £500 or do you want to spend £500 per eyepiece? Or maybe your budget is £150 and you're after three eyepieces?

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As Qualia has already said, I think I'd use the 'scope for a while before diving straight in with EP purchases.

The SW 25mm isn't usually that bad at all, so if budget is tight, I wouldn't look to replace it straight away.

The 10s can vary apparently, but you'd need to wait and give it a go before deciding whether you could live with it.

BST are a good place to start, but I wouldn't get a 5mm to begin with. I know people have already mentioned all the theoretical and practical magnification limits, but in my experience from a rural site, a 5mm is for nights of very good seeing/transparency.

The 8mm would be a safer bet (or a 6mm if your back garden is dark, but BST don't do a 6mm!).

Cheers

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Beardy30,

Another vote for the BSTs from me. They retail for about £49.00 each at the moment and really do work well with the 200P scope that I have.

You can buy them from Skys The Limit (they are sold via an Ebay shop). Alan, who runs the business is a great guy to deal with, very helpful!

As you can see from my sig I have a mixture of eyepieces (a collection built up/changed over some time btw!), some were quite costly, but even so, work very well with the modest 200P that they are used in, not overkill at all, in my humble opinion :smiley:

Regards

Doc

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As Space Beagle has said the 5mm is better on Planets and the moon in good seeing conditions i hardly use mine the 18 and the 8 get the most use i have just bought the 15mm so will be giving that a go, the 25mm that came with the scope is not a bad eyepiece  so the 18 either the 15 or 12 and the 8mm would be good starters for you that said the 15mm was voted best in its class by sky at night magazine that is why i bought it instead of the 12mm but i will be buying the last two in the set.

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Bst 25mm,12mm and 5mm.

Nick.

Yes, I agree with that. Now we have a budget the choice gets much easier !

For a little more flexibility your £150 could buy you 4 Vixen NPL's which are also nice eyepieces I feel. In this case the focal lengths I'd go for would be:

6mm = 200x

8mm = 150x

15mm = 80x

30mm = 40x

It's good to have a couple of higher power options.

The 3x BST Starguider option is also good though.

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I never said that Wookie, mind you I do agree about the 5mm.. :smiley:

The whole set seem to be good quality ep's for the cost and do seem to work well in my f5 scope!

I meant that being high magnification which you said would be better on Planets and moon i didnt explain as  good as i should sorry if i offended you there was no intent.

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Beardy30.........( Space Beagle) ...Hi,  When I referred to overkill, I dont think spending 200-600GBP on a lens is always necessary. The optical quality and construction of a Tele Vue Delos for example may be the dogs, but their only as good as the light and resolution presented to them from the telescope. I dont doubt they work very well, but if conditions are poor, they wont improve the image any more than the supplied 25mm kellner that a Skyliner provides. Sorry If  misleading!.  

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Beardy30.........( Space Beagle) ...Hi,  When I referred to overkill, I dont think spending 200-600GBP on a lens is always necessary. The optical quality and construction of a Tele Vue Delos for example may be the dogs, but their only as good as the light and resolution presented to them from the telescope. I dont doubt they work very well, but if conditions are poor, they wont improve the image any more than the supplied 25mm kellner that a Skyliner provides. Sorry If  misleading!.  

Sorry but I disagree with this on the basis of personal experience. Quality eyepieces will allow the scope to deliver the very best it can under the prevailing conditions without adding any aberrations of their own.

The Skyliner 200P is an excellent scope (as you know !) and will benefit from top quality eyepieces.

You don't need to spend £hundreds on Pentax XW's and Tele Vue Delos's though. If you can accept the smaller field of view and tighter eye relief the Tele Vue plossls, Baader Genuine Orthos and Astro Hutech orthos will deliver image quality as good as these more exotic brands for £50-£80 a throw.

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Beardy30.........( Space Beagle) ...Hi,  When I referred to overkill, I dont think spending 200-600GBP on a lens is always necessary. The optical quality and construction of a Tele Vue Delos for example may be the dogs, but their only as good as the light and resolution presented to them from the telescope. I dont doubt they work very well, but if conditions are poor, they wont improve the image any more than the supplied 25mm kellner that a Skyliner provides. Sorry If  misleading!.  

Edit: Pipped at the post by John ;)

Premium eyepieces are about more than simple optical equality. Build quality, eye-relief, apparent field of view all come into the equation. You certainly don't need to spend a fortune to get the best quality of view. The 6, 10 and 18mm Baader classic orthos would be right up there. But, the eye relief is tight if you wear glasses and the apparent field is only 50°, the low price is reflected in the construction (compared to the old BGO's for example). 

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Beardy30.........(John)   ......maybe my play on words, but I feel the scope has already delivered to the focal point, the eyepiece cant interfere with that, it can only use whats there, and  If that delivery  is inferior in anyway, the lens really cant help that much, but If the light and resolution is perfect, then there`s no argument, the quality lens wins.( RikM ).....likewise, there is much  more than just optical quality. I see from your posts, your light years ahead of me. Me, I just want to try and simplify things for people. After all, its  just opinions and observations.

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