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The Warthog

Eyepieces - the very least you need.

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TV's are nice but Warthog wrote this back in 2009.

I have TV plossl's but also the BST Explorers and find I am equally happy to put either in any of the scopes I have.

I don't think when Warthog produced this BST, or Astro Tech Paradigms as they are, were around.

Not even sure that that other ones such as Celestron X-Cels were either, or if they were they were more of an unknown factor.

TV's are nice but from the general feedback you will not go wrong with either BST Skyguiders or Celestron X-Cels.

I bought the TV plossls for the reason that they had a good QA system and a bad/poor one was unheard of, well the other two mentioned seem to have good QA applied.

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Indeed!

The middle ground does seem to have improved greatly over the last few years. However, issues can arise with the faster 'scopes.

Meissa, you have to decide for yourself! If you're happy with the BSTs in your 12" then there's no problem.

The Explore Scientific 82o range are a notch up without getting into TV territiory. But get yourself to a local observing session where you can compare and (possibly) try them in your own 'scope.

Only then can you decide if you're content with what you've got or are willing to save for the TVs.

But, isn't it a bit like life in general? We don't all save up for porsches, most people manage quite nicely with a Ford Fiesta/Escort. There wouldn't be the increasingly diverse range of EP suppliers if only TV will do.

Like lots of products, EPs are on a sigmoid curve, there are duff ones at the bottom for peanuts to be avoided at all cost, the greatest quality to price benefit is in the middle, but if you want to squeeze every last photon out of your equipment then that's where the top of the range come in.

You just have to find where you fit, what you're happy to spend and be very content with the lovely sights possible from your own back garden!

Cheers

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+1 for celestron x-cel. I used them in a 12 dob and views through them was excellent. Also if you only want one extra wide field ep the maxivision 24mm 82degree eps come in at around £130 and that would be a great addition to top off x-cels.

http://www.firstlightoptics.com/celestron-eyepieces/celestron-x-cel-lx-eyepiece.html

The 18& 12 plus a two times barlow gives you a great range, chuck in the maxivision and u really would have a great range.

Sent from iphone.

Edited by bomberbaz

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Well my a ope is a 6f/8.3 scope and I got a mixed bag from my low end low power eyepieces like a uo 24mm Koning And my mid-range is a 12.5 Antares orthoscopic and I got a nice set of TMB planets ties for high power viewing with the planets from a 4mm to a 7mm And celestron 2x Japan ultima Barlow lens DAle

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Great post Warthog, really simplified what sometimes seems confusing to us newbies!!

Thanks so much,

Mark

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Even four years after it was initially posted, a great, informative read that is easy on newbies. These helpful posts by veterans are the stuff for which people sign up to SGL. I certainly did.

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Brillaint post and one that's helping me, I am pretty useless at maths so the spreadsheet above will come in handy (thanks for that).

Would just like to check that I'm buying correctly before hitting the Purchase button!

Sky Watcher 130pm scope owned:

To Buy - Skywatcher 2x Deluxe Achromatic 1.25" Barlow

To Buy - Skywatcher SP Plossl eyepieces 17mm and/or 20mm

I'm not rich so cant afford the more pricey models, but not sure if there's a vast difference between 17mm and 20mm? bearing in mind they are out of stock of the lower EP anyway, bit lost with that so thanks for any help in advance!

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Should have read it before starting!!

What I have noticed is that eyepiece package supplied with a scope a will get you by but don't have the clarity of better eyepieces.

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Just wanted to say my thanks to a great guide, I am a total noobie to this game and after owning my first starter scope for a couple of months now am at a stage to buy some new eyepieces. Being new all the numbers and focal stuff shot over my head like a shooting star. After reading this article I now have some grasp on what I am doing, your post is extremly easy to read for a noobie like myself and for that I am very greatful.

Daz :biggrin:

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Like many others have said this post is exactly what I was looking for too. an excellent, easy to understand guide on EP's.  As a newbie looking to put together my first EP collection with my new scope, due in a few weeks, and not wanting to make costly mistakes buying rubbish I think this guide is invaluable.

Many thanks Warthog

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I'm glad everyone is finding this guide helpful.  Myself, I find some of it quite confusing...

e.g. this.

Suppose you have a 10", f/5 Dob. You will have a focal length of 1250mm, and will get 200x with a 6.25mm eyepiece.

In practical terms, a 6.5 to 7.5mm eyepiece will be what you will find available.

Yep, I totally get this.

This though

To get a 5mm exit pupil out of a 250mm mirror, you will need an eyepiece that gives you 50x. This means a 25mm eyepiece.

To get a 7mm exit pupil out of the same mirror means a magnification of 36, and a 35mm eyepiece.


I don't get what he is saying here - at all.

And then there is this

If you can afford slightly better eyepieces, then buy those, with the length guidelines still in mind.

Exactly what, constitues "better eyepieces"?

Not really much in this guide that explains the differences in eye pieces?  This is just mostly talking about mm.

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Well,.......that makes things very clear....THANK YOU.  It puts everything I need to know into a concise...easily understandable post. Maybe it should be a sticky?

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I have a question regarding objective lenses: Is there a single standard size for the barrel or several? Only one such lens (20mm) came with my scope and the ones from my Science Museum Magnum have smaller barrels so they could actually fall right through the eyepiece holder. There's a kludge I might be able to use in that the 3X Barlow that came with the Magnum is thicker at the top end so that it will just fit and then I can use a couple of the Magnum lenses in that. However that will put the magnification way over the top with anything under the 12mm (4mm effective) I would be transferring. Nor will I have much in the way of flexibility with just 2 lenses and the Barlow giving X45, X75, X135 and X225. Or could I be greedy wanting more intermediate mag factors?

As an afterthought: Do the filters screw into the lens barrel from the bottom or the top over the final objective lense?

And another afterrthought: Are spares reasily available for a Tasco Luminova? Mine came without the top caps.

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Oops! forget the X135. That would be the 12.5mm lense which doesn't fit the eyepiece tube without using the Barlow. Damn: I must be getting old ... :embarrassed:

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I don't get what he is saying here - at all.

And then there is this

Exactly what, constitues "better eyepieces"?

Not really much in this guide that explains the differences in eye pieces?  This is just mostly talking about mm.

Exit pupil can also be found by this equation

EP = A / FR (Exit Pupil = Aperture / Focal Ratio)

It is difficult to define 'better eyepieces' because factors like eye relief play a big part (a person with glasses could not use a 4mm Abbe-Orthoscopic eyepiece with them, so in this instance this is not a very good eyepiece, and any long eye relief eyepiece would be bettter). But, generally it is defined as having less optical aberrations. However, no eyepiece is perfect so generally you have to lose out on some things (i.e. You can't have perfect correction for everything and have a 100 degree FOV and have 20mm eye relief). Many observers prefer eyepieces that are sharp, so in this case, a better eyepiece is one that provides sharpness. Here's an interesting thread for you to read:

http://stargazerslounge.com/topic/180987-eyepiece-designs-and-sacrifices/

HTH 

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I've got a Celestron Astromaster 114EQ with a focal length of 8.77 so have I worked it out right that I need? (as close as possible):

High power eyepiece
6.58
Med-high
10.96
Med-low
17.5
Low
26.3
It comes with a x10 and a x20

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I've got a Celestron Astromaster 114EQ with a focal length of 8.77 so have I worked it out right that I need? (as close as possible):

High power eyepiece

6.58

Med-high

10.96

Med-low

17.5

Low

26.3

It comes with a x10 and a x20

According to Celestron the focal length of this telescope is 1000mm (It achieves this in its shorter tube length by using a kind of in-built Barlow lens). You should use this figure to recalculate your 'ideal' eyepieces.

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I've got a Celestron Astromaster 114EQ with a focal length of 8.77

I think you meant F8.77 here, your calculations looks right to me.

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I would suggest that when buying eyepieces you factor in the odds that you might want to progress to a bigger scope in the not-so-distant future. If it's on the cards and you're 'made an offer you can't reuse' (horse's heads optional) then why not pick up a damn good lens or two that are beyond the capabilities of your current setup? Astronomy aside I've bought many tools several months or even years before I've had much - if any - use for them and later congratulated myself on the savings considering how much they cost by that time.

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Please be aware that Plossls have very short eye relieve at short focal lengths, meaning that you need to put your eye right up against the eyepiece.

Have you read the sticky at the head of this section:- http://stargazerslounge.com/topic/43171-eyepieces-the-very-least-you-need/

Generally you won't need to go much above 180x-200x.

Hi, yes I read that thread & notived that one person also a novice was advised to start a thread specific to his/ her scope, as it gets a bit bewildering on there for a novice.

Is there another type of ep you would recommend besides plossls then ?

Thanks for the reply

Hi spiral . I'd advise reading this.

http://stargazerslounge.com/topic/43171-eyepieces-the-very-least-you-need/?view=getnewpost

Power and high magnification is not the be all and end all . Most deep sky objects will require low and medium powers .

As for collimating the telescope . It's not difficult to do and I'd say get yourself a Cheshire collimating tool , they are simple to use and do the job , some may recomend lasers but it's down to personal preference .

High power is useful on some objects. , the moon and planets for example, but even then you need to stick within the limits of the telescope you use and take conditions into account.

Hi, its the ex two strike bike tuner in me that always wants to extract maximun power ;-)

I think I will go lower than a 4mm then, I have just seen a nice 5mm from a link on another ep thread that might be the answer, I'll definately get the Cheshire, thanks.

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