Please help me choose some quality eyepieces

[Astronut]

I'm looking into getting a Meade 12" truss dob. very soon but eyepiece research is bogging me down.

The focal length is 1524mm with a focal ratio of f/5

I've done some homework on suitable eyepiece focal lengths and have arrived at following conclusions:

a 1mm exit pupil is the minimum recommended and a 5mm exit pupil is the maximum recommended for someone my age ie. rapidly approaching 50 (7mm for someone younger) - is this correct? I have read elsewhere that the commonly quoted minimum size limit of 1mm is an internet propagated urban myth and the maximum limit of 5mm or 7mm (makes more sense given pupil dilation) can also be taken with a small pinch of salt and 10mm is acceptable providing it's not your only eyepiece.

So, assuming there's some truth in the above and according to the calculations

exit pupil = mirror aperture / magnification OR exit pupil = eyepiece focal length / mirror focal ratio AND magnification = mirror focal length / eyepiece focal length

this would give me a range of focal lengths from 5mm to 25mm with approximate magnifications from x305 to x61.

x300 is commonly quoted as the maximum practicable magnification given the usual seeing conditions and is well within the range of the x600 the mirror is capable of giving (50 x aperture in inches) so x305 would be OK - yes?

If I went for a 0.5mm exit pupil, I would be able to get a 2.5mm eyepiece which I think would be pushing it on magnification (x600 + :nono:) so that rules that out. If I went for a 10mm exit pupil, I would be able to get a 50mm eyepiece giving a low magnification of approx. x30. Ok, there'd be some stray light falling on the iris but what a nice wide field that would give and with a wide-angle eyepiece I can only imagine the view would make my jaw drop

I haven't even looked into eye relief (distance of exit pupil from eyepiece?) and I'm not aware if there's a calculation for it but I want eyepieces with comfortable eye relief. I wear glasses for short-sightedness but I take them off for the eyepiece so I don't want excessive eye-relief, just enough so I'm not pressing my eyeball too close to the eyepiece.

The eyepiece supplied with the truss is a 2" Meade series 4000 QX 26mm with an apparent FOV of 70 degs and eye relief of 17.8mm - ample eye relief and quite a wide field but is this a better than average eyepiece?

Also, am I correct in thinking that 2" eyepieces are more suitable for low power but might be a waste of money for high power?

Is there any advantage to using a 2" eyepiece over a 1.25" eyepiece in high (or even low) magnification?

I'm not too concerned about prices yet either but I may be when I total it up

I just want to know what would be the best selection to get the best out this 'scope? I've read naglers are highly reverred but pricey - would I be going OTT getting a set of these.

I'm thinking maybe 3 or 4 eyepieces + a x2 barlow might give me a good range.

Over to you, good people. Any suggestions welcome.

[GazOC]

I'm not sold on the exit pupil method as you still jsuts end up checking that you have a good spread of magnifications and older people are put off getting a widefield eyepeice beacause the exit pupil is greater than 5-6mm. Just get a good spread between x300-x250 and x50-x40. The 25mm shouldn't be your largest eyepeice as you'll want a 32mm or 40mm widefield 'finder', if you go as high as 50mm you may start losing too much contrast from the central obstruction of the Newt.

2" eyepeices are generally used when the view they show cannot physically fit in a 1.25" field stop.

You'll need to find out whether the eyepieces you are looking at give good views in short focal ratio scopes as they are very fuusy over eyepieces. A good eyepeice in a f10 scope may be awful in a f5 scope, particulary eyepieces with wide AFOVs.

BTW the Baader Hyperions may be worth a look, I use a set in my f4.5 Dob. I don't think you can do much better for the money.

[Astronut]

BTW the Baader Hyperions may be worth a look, I use a set in my f4.5 Dob. I don't think you can do much better for the money.

Do you get much coma with these in the f4.5 dob?

Even Mr. Nagler recommends using a coma corrector (ParaCorr?) for reflectors f/5 and lower and that's with Nagler and Panoptic eyepieces! - maybe that's just a marketing ploy.

Do you use a corrector on your dob. or do you just tolerate any coma?

I'm having trouble picking out short focal length eyepieces - it's difficult to choose the right focal length for the highest power. If I choose one that gives me a little too high magnification (say x330 +), I might end up being limited to using it only 1 or 2 nights a year (or never!) depending on the 'seeing'. Conversely, if I choose one that gives say x260-270, I might not be close enough to the limit, if you see what I mean.

With this in mind, I've been looking at the Televue zoom 3-6mm - I like the concept of it. According to what I've read, it can be fine tuned to pick a focal length in between each the 'clicks' of 3,4,5,6mm depending on 'seeing'. It would give me a range between x254 - x508 How good an eyepiece this is, I don't know, but from what I've read so far, it can't be half-bad if it's a Televue

It's a tad pricey at around £320 but it's like having 4 Televue radians in one. I may just treat myself.

I'd like a wide-field 2" eyepiece but again, it's proving difficult to compromise between focal length and AFOV.

I may end up paying more on eyepieces than the 'scope itself at this rate - maybe I should have resisted temptation and not even looked at Televue's site

The 31mm Nagler 5 is way over the top at £500 though and I definately can't justify paying that much for a wide-field. The 35mm Panoptic is quite a bit cheaper but is it really worth it to spend that much on a wide-field eyepiece - I really don't know. It is tempting though, I'll say that much. Could I get by with just 2 eyepieces?

I have to consider the issue of filters too - I don't want to end up having to buy 2 sets of filters - 1 for 1.25" and another for 2". Maybe there's some sort of adaptor for attaching a 2" filter to a 1.25" eyepiece?

I'm not a high earner, by any means, but I sometimes think I've got more money than sense but then again I've nothing else to spend it on (at the moment)

Maybe I should just get the 'scope 'as is' first before I go silly spending. One step at a time, as they say.

[edit]

I just read this and have found it very informative. It's also made me think again about spending silly money on eyepieces.

http://www.cloudynights.com/item.php?item_id=366

I still like the look of the Televue zoom though for high power.

I'm thinking I need at least 3 eyepieces now, not 2 - I was forgetting about the 'sweet spot' (focal length of roughly 2 x focal ratio).

Maybe I should just get a set of good quality parfocal plossls and a decent barlow and forget about the 'spacewalk' factor.

I used to have an Erfle eyepiece back in the '80's on my newt (f7 or f8? - can't remember) and I remember the view of M42 was spectacular. That was the widest field eyepiece available at the time. It was about 65 degrees, not so wide by today's standards, but i had to move my eyeball around to take all the view in. I think I'd be happy again with that amount of wide-field.

[/edit]

[FLO]

I'm thinking I need at least 3 eyepieces now, not 2 - I was forgetting about the 'sweet spot' (focal length of roughly 2 x focal ratio). Maybe I should just get a set of good quality parfocal plossls and a decent barlow and forget about the 'spacewalk' factor.

Good idea

I used to have a collection that included Kellners, Plossls, orthos, Lanthanums, budget super-wides, Panoptics and Naglers (including the 3-6 zoom) but sold them all last year and settled on an eyepiece set. There is a lot to be said for having a number of good quality Plossls or Super Plossls that share the same optical characteristics and FOV.

Of course, I reserve the right to weaken and fall under the spell of an exotic brand ..... :drunken:

[Andrew]

This is not the most objective post since I haven’t looked through a very wide range of eyepieces. However, if you’re willing to spend serious money on eyepieces I’d consider a Pentax.

I have a similar scope to the one you’re considering ~ A 300 mm f5.3 dob with a focal length of 1590 mm. The eyepiece that I use most often is a Pentax XW 10 mm. It gives x159 which is about as much power as seeing conditions allow on a typical night for me and a FOV of just over 26’, which is ample to encompass the majority of objects (although not of course everything). In my scope it also gives pin point stars across the whole FOV (unlike anything else I’ve looked through). Cloudy nights has a series of reviews/discussions dealing with the Nagler vs Pentax debate and opinion is divided about the relative merits of each.

If possible I’d certainly try to have a look through some different eps in your scope before parting with that kind of cash (i.e. get the scope first) – there’s always the SGL star party

[Merlin]

I like my BAADER orthoscopics. These are top quality eyepieces and they won't break the bank. I use the following orthos: 12.5mm, 9mm and 6mm. Above these, I use TELEVUE Plossls: 25mm and 15mm. Above these I have a 40mm Super Plossl for low power sweeping.

You'll get greater clarity and brightness with these "simple" eyepieces than you would with complex and costly types like BAADER Hyperions and Naglers.

[Astronut]

Steve: I like the look of the Meade eyepiece set. I was looking at Televue Plossl's last night and they seem quite reasonably priced (quite cheap compared to the other exotic varieties they do) - I believe they invented the Plossl but I may be mistaken (I'm suffering from information overload and lack of sleep ). The Meade set have a wider AFOV of 60 degs compared to the Televue's 50 degs which is nice. This means the 32mm Meade would give me a FOV of 1.26 degs which is quite a decent wide field - probably comparable to that Erfle I used to have. I'll have a read up on them particularly on how well they perform (re. coma) on an f/5 'scope.

I'll be contacting you soon regarding purchasing the Lightbridge. I'd like a weekend delivery but if that's not possible to arrange, I could drive down and collect when it's ready.

Andrew: It's reassuring to know that you're not seeing coma on your f5.3 dob. with the Pentax eyepiece. I'll dig out those cloudynights.com debates re. nagler vs. pentax. I've not really looked at the Pentax's in any detail yet. The SGL party might not be do-able for me as I may be working the day after (it's on a Saturday, right?) - would like to go though, as I'll hopefully have my Lightbridge at that time and it would be a good opportunity to test it in the field

Merlin: Like you, I'm beginning to think that less is better ie. less glass = brighter views - makes sense to me anyway I'll have a look at Baader eyepieces too.

[GordonCopestake]

Televue didn't invent the plossl but they make the best ones and have done since the 80's (70's?). Many modern eyepieces can compete with them for FOV and contrast but for the price, brightness and crispness I doubt you can beat them for the price

[edit]

http://en.wikipedia.org/wiki/Georg_Simon_Pl%C3%B6ssl

The plossl was invented by Georg Simon Plössl in 1860!

[Astronut]

Thanks Gordon - I've just got back from surfing the net and the general consesus is that Televue Plossls are the best plossls as you say. The only thing that worries me about them is the short eye relief in the short focal length versions.

I was looking for information on the Meade 5000 Plossls and I read one worrying report at iceinspace (australian forum) from a guy who said he had reviewed the entire range of the Meade 5000's and he had come to the conclusion (about the super plossls)... "The 60 degree field is too wide for the correction of the design and all had serious edge-of-field astigmatism and aberrations". His words, not mine. I assume 'correction of the design' means adding extra elements to give a wider 60 degree AFOV. He didn't mention which 'scope or 'scopes he was using though. He also said that the Meade SWA and UWA eyepieces were... "much better and in a different class".

It's difficult to sort out the fact from the fiction and the above is just one guys opinion.

Steve at FLO seems to like his set though.

Question for Steve: What 'scope are you using for your Meade 5000 super plossl set?

I've read alot of glowing reports about the Meade 5000 SWA 28mm and I'm beginning to think this may be a good choice for a wide-angle eyepiece. The exit pupil on this would be 5.6mm which is close to the maximum of anything I'm considering.

A review at cloudynights was particularly favourable from a middle-aged (like me) user and he was using it in a 16" f/4.6 and he was wearing glasses!

ohno damn my bath water's gone cold - I've been surfing for hours - again!

[GordonCopestake]

They dont go below 8mm for that very reason: short eye relief. Even the 8mm is a bit short, but thats the nature of the design. If you need more eye relief look at radians or LVW's instead

[FLO]

Question for Steve: What 'scope are you using for your Meade 5000 super plossl set?

Whatever comes my way...

The fastest so far has been f5.

Whilst they are no match for a Pentax XW or TeleVue Panoptic, they are remarkably good for the money.

You are welcome to borrow one of mine It might break you free of this paralysis thru analysis

[Astronut]

Thanks for the offer Steve - very generous of you. If I can get to the star party, I'll try one out.

No.1 priority is to get the 'scope asap.

I've been doing further eyepiece research and have narrowed my choice down to Meade 28mm 5000 SWA for low-power, Pentax 10mm XW for mid-power and Nagler 3-6mm zoom for high-power. All seem to get good reviews in fast dob's. (I reserve the right to change my mind again at a moment's notice )

After arriving at this choice, I found a review of the Pentax 10mm and 14mm XW's over at cloudynights and the reviewer has the Meade 28mm SWA also in his small collection of eyepieces. He uses them on his 16" f4.6 truss dob and is very happy with them.

I think one of those Moonlite focussers would be a fine addition too

Expensive choices but you can't take it with you as they say

[russ]

Thanks for the offer Steve - very generous of you. If I can get to the star party, I'll try one out.

No.1 priority is to get the 'scope asap.

I've been doing further eyepiece research and have narrowed my choice down to Meade 28mm 5000 SWA for low-power, Pentax 10mm XW for mid-power and Nagler 3-6mm zoom for high-power. All seem to get good reviews in fast dob's. (I reserve the right to change my mind again at a moment's notice Wink )

After arriving at this choice, I found a review of the Pentax 10mm and 14mm XW's over at cloudynights and the reviewer has the Meade 28mm SWA also in his small collection of eyepieces. He uses them on his 16" f4.6 truss dob and is very happy with them.

I think one of those Moonlite focussers would be a fine addition too Smile

Expensive choices but you can't take it with you as they say Wink

my god you did well to pick your way through that thread and come up with that selection. :shock: Must be a couple dozens eyepieces recommended in this thread, from just about every type. Just goes to show there is no definitive eyepiece choice...everyone has a personal favourite and what works for one person probably won't for the next. Some people like comfort (Lanthanums, Hyperions, Radians), others like purity (plossl, Ortho) but if you want both (Pentax XL, Panoptic, Nagler) you pay through the nose.

I think you did very well, don't doubt yourself now. You could be here all year

[GordonCopestake]

My eyepiece collection has recently been blown out of the water, but it looked something like this:

I was quite pleased with that line up (other than replacing the 30mm 80 degree with a 31mm 82 degree)

That being said, I'm seriously looking at the hyperion zoom though to replace the 11mm T6 and maybe even the 24pan. A 3-6, 8-24 range covers 99% of stuff I think.

[FLO]

I used a Meade 28mm SWA for a while and really liked it!

[Merlin]

Gordon's advice about using Radians or some other "complex" eyepiece to give wide fields with high mags defeats the purpose of maintaining the maximum clarity and brightness we get with "simple" eyepieces. Gordon's a wide-field freak,aren't you,Mate?

[GordonCopestake]

it depends on the target. If i'm viewing saturn etc then FOV makes no difference and orthos give the best views (or my 3-6 zoom). If i'm looking at DSO's then I want as wide a FOV as possible with the highest magnification.

[Astronut]

It depends on the 'scope used too.

Wide field, I would think, would be a positive boon on an unquided dob. This factor has been an infuence over my choice.

[GazOC]

I was more than happy with my orthos until I got a Dob (and still use them on my motorized mounts) but they are just not practical to use on a 1350mm focal length Dob - you need more eyerelief and FOV. I plumped for a set of Hyperions, they seemed to offer the value/ performance ratio that suited my wallet. I'm still happy with the choice.

[FLO]

Wide field, I would think, would be a positive boon on an unquided dob.

Definitely.

[John]

The 1st quality eyepieces that I ever bought, in the late 1980's were 3 Tele Vue Plossl's. I eventually sold them to get something more exotic and have tried quite a number of brands and types over the invervening years but I've now gravitated back to Tele Vue Plossls again - I'm picking up the 25mm on Monday which will complete my 1.25 inch set; 8mm, 11mm 15mm, 20mm, 25mm and 32mm. I've not bothered with the 40mm as it won't show me any more sky than the 32mm.

I've found that these perform very well right across the field with all types of scope and, for me at least, I feel that I'm getting the best that the scope and conditions allow when I'm using them. They perform very well with my Celestron Ultima Barlow and they are parfocal as well so only minimal re-focussing is needed when changing eyepiece. Another bonus is, IMHO, that they are not too expensive when they crop up used - £40-£50 apiece.

Everybody has their favorites - for what it's worth mine are TV plossls