Planetary Eyepiece advice

[209herschel]

Hello everyone,

I'm looking to get an eyepiece to the moon and planets. I'm uncertain as to whether to get one immediately and get something in the $150-$200 category or perhaps wait and get something better at the end of the year. Any thoughts on comparisons would be appreciated.

I have a 10" Dobsonian, f5.

In the $150-$200 category, I'm looking at the:

Explore Scientific 8.8mm.
Baader Hyperion 8mm
Orion Stratus 8mm

If I wait, I'm looking at:

Televue Delos 8mm
Pentax XW 8mm
Televue Nagler t6 9mm
Vixen LVW 8mm

My question is whether the more expensive categories are significantly better than the first group? I usually wear glasses when viewing but my astigmatism is slight so I could get used to not wearing glasses.

If you think there are some other ep I should consider alongside the above, I'll certainly value the advice.

Thanks very much.

[GrahamL]

I had a pentax XF 8.5 for quite a few years and found it a great planetary eyepiece, go so far to say its a better buy than quite a few of those on quality alone , even better its a cheap to buy ! :)

have an 8.8 es now , great little eyepiece too, love the *82
planets I'd still go the XF over a lot of others,, great eypiece.

[brian nordstrom]

:) Hi Hershell , over many years I have owned and liked nearly all of these except the Pentax XW , which everyone agrees is a great eyepiece and if I was in your budget range I would go for the Vixen LVW , it has a great 20mnm eye relief that will be good for being a glasses wearer , is light and easy to look thru and most importantly is a very , very good eyepiece to use as it just dis-appares when using it , I found all Vixens do this really well a nice thing when viewing intricate detail on the planets .
Oh yes personally I like the slight yellowish ? :question: tinge ( that's VERY , VERY SLIGHT ) all the Vixens I have owned over the years , about 20 of :help: them .
Try to get to a viewing night and ask for a look thru as many as possible , we amateur astronomers are friendly people and like showing off our gear ,, well I do anyway .

My 5c worth .

Brian.

[cydonia]

Hi Brian

HD Orthoscopic eyepieces are the best I have ever used on the planets. Narrow field of view but they are sharp right to the edge and contrasty. I also have a Pentax 10mm xw which is very good but I mostly use the Ortho. If I remember they are about $120 or so from Frontier Optics

[Profiler]

Hi Herschel

As another suggestion you could simply buy one of your listed "quality" eyepieces 2nd hand right now (instead of waiting for the end of the year):thumbsup:

[MortonH]

I wouldn't use the Hyperion or Stratus for planetary unless your Dob has tracking. Edge performance will be quite poor. I had the ES 8.8mm and it is good. I now have the Pentax XF 8.5mm.

Are you sure that 8 - 9mm will give you the magnification you need for planetary? I might have thought that something in the 6 - 7mm range might be better, depending on the seeing conditions where you observe. Explore Scientific does an excellent 6.7mm model.

[David Niven]

My favourite is the ES 6.7 and the XF8.5
Both are exceptional and very affordable.

[brian nordstrom]

:)Yes Orthoscopics are probably the best planetary eyepieces made and I had a full set of CircleT volcano tops at one stage as well but I don't think they would be very good in this case as the OP wears glasses for astigmatisim and the eye relief of the ortho's might be a little tight for that .
Brian.

[MattT]

How about Vixen NLV? Only $129 at Myastro shop 20mm ER with 50º AFOV. When I compared the 9mm NLV and XW 10mm I couldn't see any difference except the TFOV. I'm tempted to get the 4 5 and 6mm in the NLV. All my scopes have tracking.

[209herschel]

I'm definitely keeping my eye open for a second hand one in the classifieds. I was about to buy an ES 8.8mm a couple of weeks ago but the eye relief worried me so I held off. I've since been out without my glasses and I think it'll be fine to keep them off. So I'll probably go for that if it shows again. Cheers.

[209herschel]

Hi Matt, I was actually looking at those. It's just I thought if I was going to buy something I'd use for long time for planets and the moon, it might be great to have the extra FOV. Now I've read some people's thoughts that a wide AFOV isn't really needed on high magnification on planets and the moon. I'd be keen to hear your thoughts on that. Cheers.

[209herschel]

Thanks for the advice. I was originally going for the 6.7mm but I recently bought a Bintel 2x ED barlow so I thought I'd use the 8.8 then barlow if I made it out to a dark site. I'm undecided because I'm in my yard in Inner Sydney most of the time so the 6.7mm might get more use? Cheers.

[MortonH]

It's worth trying to figure out what kind of magnification is useable in your yard. Of course the seeing conditions are different every night but you may be able to figure out what eyepiece you can use most of the time, and save the Barlowed high mags for the nights of exceptional seeing.

I have no yard but two balconies - one faces East and one faces West. On the East facing one I can use 200x most nights in my 8" Newtonian. However, the other side looks over a busy road and the air turbulence limits me to 150x or less.

If your scope has a focal length of around 1200mm you would get 200x with a 6mm eyepiece, so that would be my starting point. But 8.8mm or 8.5mm would be good too, and could be Barlowed on those great nights when you really want to crank it up.

[MortonH]

There's a nice TMB 6mm planetary eyepiece for sale here

http://www.iceinspace.com.au/forum/showthread.php?t=123354

[Renato1]

An 8mm eyepiece would only give you 159X - hardly worth the effort in my opinion.

You'd want at least a wide angle 5mm for around 250X or 6.3 mm for 200X.

If you Barlowed or Powermated that 8mm eyepiece that you want, then you'd get 320X, which might be okay on some or many nights, depending on where you live. But it might be frustrating too.
Regards,
Renato

[209herschel]

I'm now thinking that the 8mm magnification won't be enough. I've got a 9mm plossl and while the better quality, greater AFOV might be great, I guess it won't increase the size of the view.

After reading a few things and getting some responses along the same lines as yours, I'm now thinking of something in the range of 5-7mm. If I can get by without glasses, I'll definitely go the ES 6.7mm. I'd love to get the Vixen LVW 5mm. Then if I hold off, the Delos 6mm at the end of the year would be my ultimate choice. Would you agree that the quality runs in this order?
+

[casstony]

If you're not completely comfortable without your glasses hold off for something with longer eye relief - you'll have a much more enjoyable time at the eyepiece.

[MattT]

Now your talking! Can you use the 9mm plossl without glasses?
If yes then anything is usable. I don't have astigmatism in my eyes but I believe it only shows up in longer FL eyepieces for those who do. I guess your dob doesn't have tracking so 70º+ eyepieces are probably the go….can be expensive though. Pentax XW's barlow well so get the XW 10 and 7 + a 2X barlow to give 5 and 3.5. Meade HD5000 60º eyepieces are pretty good too, cheaper than XW/Delos, with 17mm ER worth a look. As my scope has tracking I get away with narrow FOV Ortho eyepieces.
Matt

[MortonH]

I agree with that quality order. Don't forget Pentax XW - pretty much the same quality as Delos (some say slightly better).

The Delos are very expensive. I wouldn't pay full price for one. Either advertise for a used one or wait for Tele Vue to have a sale - happens at least once a year. I got my 14mm Delos on sale.

In fact, I wouldn't pay full price for any of the premium eyepieces unless you've tried one. They all have different ergonomics and sometimes that's the deciding factor between different models/brands.

[Renato1]

I can't comment on any of those eyepieces, since I haven't tried them.

If you are pushing your dob around though, you'd definitely want something with at least a 60 degree or better field of view. The 50 degree ones are do-able, but do get annoying.

The other factor that isn't mentioned much is the size of the sweet spot in an eyepiece. The eyepiece I've used most over the years has been my old 6.4mm 5 element series 4000 Meade Superplossl. When S&T did a comparison, they found that the Televue Plossl was slightly better at the sweet spot than the Meade, but that the Meade had a much bigger sweet spot covering most of the field. See the problem? While better, the Televue would be harder to keep in the sweet spot for the best view than would the be the case with the Meade. So try keep an eye out for this factor in reviews that you read for the wider angle eyepieces -probably the newer Televue eyepieces address this.

Also, a lot depends on where you live, and how quickly your dob cools down, and how well collimated it is. The best views of the planets I've ever seen with any of my telescopes have been through my 14.5" f/4.5 dob - but that was extremely rare and always at the end of a four hour observing session. So - depending on circumstances, you may not actually wind up using the expensive eyepiece that much or you may. Perhaps if you got an inexpensive Barlow and used it with your 9mm, you'd get a good idea of how quickly things settle down, and how often you would use a better quality eyepiece.
Regards,
Renato

[209herschel]

Thanks very much for all of the advice. I don't have tracking so I'm leaning toward as wide a field as I can afford. I'll look into the Meade ep now. I've got a 2x Barlow, bintell 2" ED. Would you all recommend something like a great 9mm ep that I could Barlow or would I get better results with a 6mm ep that isn't barlowed? Would a Barlow affect the quality of the view significantly? Thanks again.

[MattT]

In that case the ES 82º 11mm and 8.8 barlow beautifully. The only problem is short ER, not as bad as a 9mm plossl though. I'm not a TV type but will say the TV barlows are the best. Your 2" GSO will be fine, I know I have one!
Can you borrow an ES to try it out?

[209herschel]

Thanks very much. The 8.8mm and 11mm get rave reviews everywhere also, even more so than the 6.7. If they barlow really well, I'm thinking the 11mm because 5.5 is pretty high, probably be about as good as I could possibly try in the yard.

I've only ever looked through my 9, 15 and 25mm GSO plossls! So my intention is to get to an event as soon as I can. I've kept my glasses on with the 15 and 25 and it wasn't too bad so I can't see how the ES pieces would be so bad. I also think I should be fine without glasses - I think it's really just a habit in that I never really take my glasses off. It's just so hard to go past the ES pieces, they seem such great value for money. Cheers

[MortonH]

I had the 11mm and 8.8mm ES82 eyepieces. The eye relief on the 11mm was particularly short, so I didn't keep it long.

I later sold the 8.8mm in favour of a Pentax XF 8.5mm, despite the narrower FOV.

You might want to consider the TMB planetary eyepieces. They go for around $60 used these days. Maybe get a 9mm and 6mm or 5mm to see how you like them. If they're not for you I'm sure you'll get your money back on resale.

[bratislav]

Given that you have undriven telescope, there are two things you can do.

1. get a Paracorr. That will allow whatever eyepiece you get to work much more than approx 1 mm circle you get to play at f/5 before coma destroys the image. Between variable seeing and you nudging the scope all the time, chances of seeing planetary detail get to zero rather quickly. With Paracor, planet can drift from edge to edge and stay as sharp as it was in the middle. If you get a well corrected, wide angle design (I've seen Type 1 Nagler 4.7 go for as low as 100 bucks) you suddenly have many minutes to observe, not mere seconds at the time.

2. (better) Make a platform. Driven telescope will allow you to see much more on planets.

Contrary to popular belief, the eyepiece plays only a few last few percent in planetary work. That is, a high quality mirror on a driven mount with a cheap Chinese Plossl will work million times better than an average mirrored, undriven scope with a $$$$$ Zeiss Abbe Unobtanium polished by Norwegian virgins using Rouge made from rusting samurai swords during a total solar eclipse.

[N1]

Want!!! :rofl:

[209herschel]

Hi there, I had a look at this one. I've tried checking the specs but I'm a little confused. There's a 9mm planetary II that's going in the classifieds for $45 but this 6mm was $100. Is there a difference or were there different series of the TMB Planetary II? I think I'll go with the 9mm. It has 12mm eye relief so I'll then know if the ES 6.7mm eye relief will be ok. It also has a 58 degree field so a bit better than my current 9mm plossl. I'll try to barlow it also to see what it looks like at 4.5mm.

[astro744]

I would put driven platform first and foremost as a moving object is more difficult to concentrate on even if the entire field is sharp although the Paracorr option is a good idea.

With regards to your last sentence your limiting factor is your "average mirror". Put the good Zeiss eyepiece on a premium mirror and you will notice a difference.

Good eyepiece + good mirror = good view
Good eyepiece + bad mirror = bad view
Bad eyepiece + good mirror = bad view
Bad eyepiece + bad mirror = bad view

Your eye, local seeing, collimation and a few other factors also come into play.

Note I'm not saying all expensive eyepieces are good or all cheap eyepieces are bad. Just remember the eyepiece is half your telescope.

[bratislav]

Not even close. A cheap (not defective! just cheap) eyepiece will show you close to 99% (on axis) of what a "premium" one will, even in a perfect scope.
You will need a special subject (say, tiny low contrast details on Jupiter), once in a year seeing and lots of patience to see the difference between a ZAOII, AP superplanetary or TMB monocentric and an inexpensive no brand Ortho ("Tanny"). Been there, done that. Sold my "premium" set.

Read what people like Dragesco and Texereau have to say about it. Newsgroups and blogs are hardly a reference when it comes to optics.

[astro744]

Are you using a premium mirror or an average one? The view is only as good as the lowest common denominator.

Note I did not equate cheap with bad so my Boolean algebra still applies.

[Renato1]

I read below where you only have GSO eyepieces so far - I find them decent enough, but not wide enough for when pushing around a dob at higher power.

If you are going to get into going to dark sites and hunting faint galaxies, nothing beats a 2mm exit pupil. Just multiply the exit pupil you want by the f ratio, in your case 2mm x5= 10mm eyepiece. If you get a coma corrector that adjusts the f ratio, you'd get a different eyepiece result.

And, that 2mm exit pupil eyepiece should be as good and as wide an angle as you can afford. A 9mm eyepiece such as you have and were thinking of getting, will give a slightly smaller exit pupil. That makes it a bit harder to find galaxies out in the country, but gives slightly more pleasing views in light polluted skies.

Apply a good quality 2X Barlow, or even better a Powermate, to that 2mm exit pupil eyepiece, and you have a nice high powered view.
Regards,
Renato

[bratislav]

Your "logic" implies that both objective and eyepiece contribute the same amount to image quality, which is very, VERY far from the reality.

Objective must deliver the wavefront with unbelievable precision; in case of a good planetary telescope, the maximum allowable wavefront error is in order of 1/10 wave (~1/20 on the optics). The eyepiece's task is to only magnify this image and deliver wavefront that is contained within eye's ability to resolve (which is several arc minutes). In case of planet observation, this condition has to be met only on axis (and near it).

Virtually ALL eyepiece designs that you can buy today will satisfy this condition. All of them. In other words, eyepiece tolerances are many thousands, if not millions of times more loose than those for objective side of the telescope. Good mirror or lens is made by a master optician and travels many many times from polishing machine to testing apparatus and back, often tested on the sky (star test) or interferometer before it is declared good enough. Eyepiece lenses are made in bulk by automated machines with no testing whatsoever of its optical surfaces (yes, even those at Zeiss and Leitz).

Have a look at on axis spot diagrams for eyepieces in Rutten and Van Venrooij's book (or more recent Smith, Ceragioili and Berry). All of them are virtually indistinguishable on axis. What you pay in a premium eyepiece is its off axis performance, first and foremost, and then we can talk about quality of polish and coatings. And those last two items make just about 1% or so of the total performance on planets.
Seeing differences in scatter (which will be the ONLY visible difference between your cherished Zeiss and my non brand Ortho on planets) is, as said before, not easy, and definitely not obvious. It requires special object, near perfect seeing and lots of patience; again, I have done this comparison, many times over the last 40-odd years. In refractors (yes, premium APOs as well as observatory class refractors like 24" and 20" Zeiss), reflectors (yes, premium reflectors with mirrors by LOMO, OMI, Suchthing, Zambuto, Galaxy, Lockwood, Barry Adcock, my own, and many others), catadioptrics (Maksutovs, SCTs, Wrights) and compound exotica (Schiefspieglers, Schupmanns) with same results.

Unless we talk about things like apparent field of view and off axis perfromance (which is totally irrelevant for planetary work), differences between eyepieces on axis are always going to be very, very small.

[SkyWatch]

Have you considered the Long Perng planetary eyepieces? I understand they are the same as the Orion "edge on", but only $79 at Andrews. I have used the 3mm and 5mm versions and they compare very well with a barlowed Nagler 13, and even my Nagler 3-6 zoom (which is magic by the way!). Not quite as wide-field (55-60 degree) as the Nagler 13, but nice and sharp across the field.
While on-axis performance is critical for any eyepiece, for a non-motorised dob it is good to have a relatively wide sharp field, even for planetary viewing, because it gives you more time looking and less pushing and waiting for the vibrations to settle again. It is really annoying if the image worsens significantly when the planet moves off centre, and this is often the case for budget eyepieces.
The LP's also have a 20mm eye-relief, which is very helpful with glasses and makes a big difference compared with plossls or orthos, irrespective of their cost.
All the best,
- Dean

[bratislav]

Only if your telescope is capable of delivering sharp images over that wide field, which Newtonian cannot, due to coma.
A 10" f/5 Newt will deliver "planetary" quality wavefront (~1/10 wave, ~1/30 wRMS or ~0.95 Strehl) over a field that is only a tiny bit larger than 1mm.

The only way around that is if you add Paracorr. Or, better, an EQ platform.

[SkyWatch]

I suspect all this is getting quite confusing for the OP.

For the record, I have a 12" f5 scope, and the eyepieces I mentioned (even the cheap LP ones) are well corrected for coma at that f-ratio, and give sharp images across virtually the whole field, so you can watch a planet pretty much from one edge of the field to the other without having to move it into the centre of the field for the whole time.

For visual use they do a great job, and are a lot cheaper than a Paracorr or an equatorial platform... ;)

- Dean

[209herschel]

Thanks very much Dean. I ended up buying a Tmb Planetary II 9mm to compare with my plossl. 58 degrees field and 12mm eye relief and they're supposed to be pretty good for planetary. I'd never even thought of the Long Perng and I knew Andrews had them. I'll start researching now - I appreciate the advice. The wide and sharp field on planetary is what I'm after before I get something great for dso which will be another topic entirely! Even with the 9mm plossl now, Saturn is pretty much through the field by the time the vibration settles and I've only seen it somewhat sharp when I've put the scope ahead and waited and had the focus on. Thanks again.

[SkyWatch]

Regarding vibration: do you have vibration-isolation pads? I have found they cut the vibration time considerably and have been very useful. Meade and Orion make them, although a lot of people experiment with their own.

[bratislav]

Sorry to say, but I find that extremely unlikely. The only eyepieces that I know of that were capable of correcting Newtonian's coma are now long defunct Pretoria line.
Which makes sense, as any eyepiece with inbuilt negative coma would be completely unusable in refractors and SCTs. No manufacturer today would deliberately cut out such a significant slice of the market.

In any case, enjoy your eyepieces; that is what counts in the end - for all of us.

[209herschel]

Actually, I didn't even know there was any such thing. I'll look into that. Thanks again.

[Don Pensack]

I agree with Bratislav, except with these caveats:
If your scope is undriven and you are pushing it to follow a planet that drifts from side to side across the field, then definitely a coma corrector like the TeleVue Paracorr is called for. Otherwise, the image will be unsharp outside of a very small area in the center.
IF, on the other hand, you add a tracking platform and you now can hold the planets dead center, then, for planets, you don't need a coma corrector and just about any decent eyepiece will show you all the scope can see in the seeing conditions under which you're observing. Seeing is the greatest factor in determining the quality of the image, not the eyepiece. There is no magic eyepiece that suddenly makes seeing better.

For wider, extended, objects, then merely having tracking is not enough, and the coma corrector becomes more important again. We have all read innumerable accounts how such and such an eyepiece is "terrible in my dob", but "the images clean right up when a coma corrector is added". Well, duh. Of course they do--you just eliminated the coma from the mirror and, in the case of a Paracorr, also flattened the field slightly.

The primary difference you'd see between the top tier eyepieces like the Delos, and a lower-tiered one like the Hyperion, is at the edge of the field. Being free from induced astigmatism, the star images in the outer 50% of the field will be a lot better looking with the Delos. Will that matter for planets held in the center? Not really. Will it matter when you are letting the planet drift across the field? Yes. But we still get back to the coma corrector once again.

Where would I put my money if I were a hardcore planetary and lunar viewer?
1) tracking platform.
2) coma corrector
3) THEN maybe a better eyepiece, though it is hard to beat the lowly Plossl for planetary images.
so, maybe:
4) Gasoline. To drive me and my scope to sites where the seeing is better.
We have a few sites around here that are that much better than average. Everyone, with every eyepiece in every scope remarks that the images are better at those sites. Just points out how important seeing is.

[Don Pensack]

Sure, your *eyepieces* are corrected for coma, as all good eyepieces are, but your *scope* is not. The coma free zone in your scope is only 2-3mm wide in the center of the field, and adds coma linearly as you move toward the edge of the field. Even if you don't notice appreciable coma at the edge of the field (and, in 50 degree eyepieces you probably won't), the sharpness of the planetary image will slowly diminish in a linear way as it nears the edge of the field. A 10mm Plossl has about a 7.5-8mm field stop, so coma certainly won't be severe at the edge in that eyepiece. But there is coma in the image as soon as you are 1.1-1.3mm away from the center of the field. That's why tracking is so important.

Or a coma corrector if tracking isn't present.

Having said all that, though, the variation in seeing that occurs will totally swamp the best correction possible:
Perfect optics + Perfect collimation + Perfect equilibrium temperatures in the optics + perfect eyepiece + tracking + bad seeing = bad image.
Alas.

[astro744]

Exactly what I was getting too earlier in the discussion, I just didn't add all the parameters as I had done so in a previous similar thread a while back.

You can also add bad eyesight to the mix. If any one is bad the result is bad.

[bratislav]

This was very educational thread; I have certainly learned a couple of things, and for that I am grateful.

[209herschel]

Thanks very much for all of that information. I bought my 10" dob from Andrews so I know there are mirrors that are a lot better but I have to say I'm really enjoying my scope. I've never had an eyepiece with greater magnification that 9mm so I thought that something like 5mm or 6mm would make a difference with something like Saturn? At the same time, I know I might sacrifice some clarity. High on my list is to try to get to a watching event where I can talk to some more experienced people. Thanks for the advice.

[SkyWatch]

Just to weigh in again: I haven't had the scope out for a while, but managed a really nice view of Saturn tonight. Very good seeing for once!

Some of the previous comments about coma in an f5 scope and the "unlikelihood" of a sharp fov with a planetary eyepiece like the Long Perng 5mm made me doubt my memory, so it was nice to have a chance to check. I understand the fov must deteriorate past the centre couple of mm due to uncorrected coma, but high power eyepieces only effectively use the centre of the field anyway. Coma is certainly present at the edge of the fov at low power, and that is where a coma corrector shines, but I must say I am not sure that one is absolutely necessary at higher power, even with an undriven scope like mine. Especially when one like the Paracorr can cost as much as the entire scope, and more than 10x as much as the cheaper high power eyepieces...

Tonight's viewing showed me the following:

The Long Perng 5mm showed a beautiful view at 300x (12" f5 scope), and I could see a sharp Cassini division and nicely contrasting cloud bands from edge to edge of the 60 degree apparent field, letting it drift in and out. The contrast and sharpness was perhaps slightly better at the centre, but it was very hard to notice any difference apart from a tiny bit of lateral colour near the edge of the fov: but almost all eyepieces show some lateral colour near the edge.

My Nagler T6 13mm (115x) was beautifully sharp and contrasty right across the 82 degree apparent fov.

I compared with a 6mm Vixen LV (45 degree fov, 250x), a 7.5mm Takahashi (50 degree, 200x), and a 3-6mm Nagler zoom.
All showed a beautiful, sharp image from edge to edge.

The Long Perng 5mm was certainly not put to shame, at roughly 1/2 to 1/4 the price of the others, and it has a wide enough fov to enjoy the view for a while before it drifts out of the field and requires moving the scope again. Much more so than (say) the Vixen. Its 20mm eye relief is a great asset as well if you have to use glasses- way better than a standard plossl. Well worth a look.

It would be nice to use a driven scope, especially at 300x(!), but because of the sharpness of the eyepieces it didn't really matter much at all if the image drifted off centre.

All the best,

Dean