Eyepiece upgrade advice

[Finski]

I'm looking for some advice as I really have little knowledge on eyepieces.

I'm getting back into star gazing and will be using 10 and 25mm pieces for a while until I can afford to start upgrading. What kind of things are worth me buying, probably one at a time, I have a Sky-Watcher 6 Dobsonian and would like to get as much out of it as possible.

Any advice appreciated!

[Hoges]

Do you wear eyeglasses? Long or short sighted can be focused out but astigmatism means you'll have to keep the glasses on, like me. Which means I have to use eyepieces with at least 17-18mm eye relief.

Personally, I love the wide field of view - 60 to 70 degrees and my most used eyepieces are a 26mm 60 degree Meade super plossle (1 1/4") or the Televue 27mm Panoptic (2")

The Baader hyperions seem pretty good value for money (I have a few) and particularly like the 17mm - a good mid magnification/good eye relief/wide field of view. I've also got a Chinese copy of it (no brand but from a Saxon dealer) which seems just as good.

Something like a 24-32mm for wide angle low power, 17mm mid power and 9-10mm for high power plus a barlow would cover nearly all bases.

Keep weight in mind - if a heavy 2" eyepiece causes balance problems it may be a pain swapping from one to the other. You might be able to pick up some nice Televue's in the classifieds from time to time - there's usually some very nice EP's in there. Some of the cheaper stuff out of China can be very good also - I'm sure you'll get lots of recommendations.

[mental4astro]

Fnski,

Do not consider the Baader Hyperion line for your dob. These are designed for refractors, SCTs and Maks as they all produce a convex focal plane. Newtonians produce a concave focal plane and these Hyperions, because of the optical mismatch will result in an image with significant aberrations that make the purchase of these eyepieces a waste of money.

These aberrations can be tolerated ( some people more than others), but the cost of the eyepiece needs to merit the compromise. Having to work with the modest budget you have, a good inexpensive 2" eyepiece for your dob would be a 30mm GSO SuperView. Also not an optical match for a Newt, but for the price the degree of aberration present is ok. If you are shelling out the same dollars that a Hyperion costs, you will find better suited eyepieces for your Newt.

The Hyperion line was most significant in my understanding of optics, in particular the relationship between scope design and EP design, and how they work to produce the final image. As if turns out, it is easier and cheaper to design and fabricats eyepieces for scopes that produce a convex focal plane. Scopes that produce a concave focal plane present a unique set of optical properties that make designing EPs to suit much more difficult and significantly more expensive to produce. Because few people take the time to properly inform themselves about optics, most of the recommendations and reviews on EPs is shrouded in ignorance and blind Brand loyalties that do nothing to progress the astro cause.

The Hyperion Zoom eyepieces actually do work really well in Newts, but the design of these zoom EPs has nothing to do with the neat single focal length eyepieces. The only thing they share in common is the same "Hyperion" name.

Another good and inexpensive eyepiece for your dob is the GSO 15mm SuperView, the smaller brother of the 30mm I mentioned above. Again not an optical match, but the 15mm shows less aberrations than its big brother. Both of these eyepieces have a generous 68° apparent field of view, which is much larger than the 52° provided by plossl eyepieces.

Another lot of inexpensive but great eyepieces for your dob are the TMB Planetary Type II line. This line while firstly designed for refractors, the complex nature of contemporary EP designs also means that some "non Newt" eyepieces can perform really well in Newts. Some better than others - take the SuperView line. The TMB line is unique that the entire line does quite well in Newts, and of course some individual focal lengths better than others, but even the poorest performer in Newts does very blooming well. I've tested the entire line fod this purpose in both Newts and refractors. The 9mm does very wel, and the 5mm is a ripper in Newts, and both of these will serve you very well. The only focal length of the TMB line I would give a miss is the 6mm. All the others for their price are great.

As for plossl eyepieces, while they are an optical match with Newts, slow ones in particular, this 150 year old design has certain practical shortcomings that newer contemporary designs leave them for dead, especially as the focal length gets shorter than 25mm. As the focal length gets shorter and shorter with plossls, the eye lens (the lens you look into ) gets smaller and smaller, while the eye relief also gets shorter and shorter until you need to park your cornea on the eye lens to look into the eyepiece.

These TMB's, making use of new glass types and newer designs mean that the eye lens across the entire line is big 20mm (yes, even for the 2.5mm!) & the eye relief is really long and easy to use. The AFOV of these TMB's is also 58°, compared to the 52° of plossls.

Now, if your budget is less restricted, it opens up other EP choices. But if you need to be careful of the $$$, the ones above will serve you very well. I still have my 30mm and 15mm SuperView eyepieces. While I've moved on to other EPs, and bought and sold dozens to have the kit I have now, I've kept these modest EPs because they are really easy for novices to use, and they are my main outreach EP's. I also have kept half a dozen of the TMB's because they are really bloody good, and I've seen them outperform $400 eyepieces!

Because of the nature of optics, I don't blindly follow brands for my eyepiece selections. Istead I use as many different EOs as I can in as many different scope types as I can, and decide for myself what works best for the different scopes I have. Most of my EPs work best with either convex or concave focal planes. Very few perform really well with both.

Alex.

[dannat]

The astrotech paradigm/ bst explorer are a good mix of value,60 deg fields and good ep design which will given u good views. Someone has a 15mm in the classifieds here

[Wavytone]

Finkski, best buy for your scope is a set of Plossls - they are an excellent match for dobs.

[doppler]

+1 for the Plossls, starting out I wouldn't go overboard buying fancy eyepieces. The eyepieces that came with the scope are most likely Plossls. You already have a 10mm and 25mm, so I would suggest a 32mm for a nice widefield view and then a 6mm for when you get a clear night and want to bump the magnification up for a bit of lunar or planetary viewing. If you are into planetary viewing a 2x barlow will double the magnification of your eyepieces so add one to your list.

[bigjoe]

+1..For these Dan..used the TS VERSION 3.2mm and 8mm Dual EDs , for viewing doubles , and left all the TVs in the case ..yes even the Deloi..there really the most surprising EP Ive ever used (great contrast)...and Ive used many!
Will buy more for my" B set"..but really, there better than that.
PS:There not TV quality but very good.
bigjoe.

[bigjoe]

I agree with this Alex; the Hyperions I had were awful in my 12 dob ..15mm Superview a surprise.
PS:Might myself try a few of the TS 6 element versions of the TMBs when I order a big APO.
bigjoe.

[geolindon]

g day Finkski,

as this moon wanes i will be often setting up in dark places south of canberra and am happy for you to try my ep's. pm me if you like.
beware though . . . . aperture fever is contagious :)

this idea has prompted another; how about a wider invite to get together?

i'll post in 'community events'

L

[Wavytone]

Joe the ones I’m most curious about - if I had a larger APO refractor with field flattener - are the APM ultra-flat-field ones. The set is a bit limited though spanning 10-30mm so you’d need something else like a 5mm SSW or 3.5mm SSW for high power.

[bigjoe]

Have not tried these Wavy....there 8 element in 5 groups , so you would think well corrected and has APMs name on them .. a Smyth or Barlow combo inside the EP would do this ..but does this have it?...or is it an entirely new design?AND what type of glass is used?
And does an Apo need a field flattener with these?
May purchase just to try out.
bigjoe.

[bigjoe]

Just found out the 30mm APM FLAT FIELD has 9 elements in 5 groups for those interested in a purchase..So you would imagine it to be better corrected across the field than a 30mm Superview with only 5 elements for example.
bigjoe.

[Wavytone]

Joe from the threads on cloudynights about these:

- they are new designs,
- they appear to be extremely well corrected, anecdotally as good or better than TV eyepieces though that hasn’t been verified by someone doing a real side by side test on a bench with the gear to measure them;
- ostensibly they’re for Flat-field scopes which strongly implies APOs with flatteners - or flat-field APOs (as mine is, a quad).
- they should also suit large long focal length scopes where the field curvature isn’t as significant as it is with small scopes. I would not recommend them for short dobs or refractors under 1600mm focal length.

The downside is they have a LOT of elements and that raises questions about ghosts and scattered light in extreme-contrast situations (lunar limb, Jupiter).

[tmz]

Wish I was close by. Awesome of you to offer, hopefully Finski takes you up on the great offer

[bigjoe]

From the look of these EPs.. looks like Marcus may have got Long Perng to design a totally different one from what we have seen before..which us a good thing; look what long Perng (owned by Synta) have done with the Esprit line and 120 ED objective for the BD range ..they should be very good then..Time will tell as usual.
bigjoe

[Wavytone]

The optical designer was a personal friend of Markus. Not Long Perng. His name appeared somewhere on CN.

The metalwork may well be by LP as I'm sure these would have been manufactured in China, and it would be quite usual to involve the manufacturer in the barrel design to optimise the assembly and testing.

Another aspect is whether these have undercuts or tapers on the barrels - in some photos they are tapered, others they aren't - and its still totally unclear what the situation is. A while back several on CN made it quite clear to Markus that most wanted straight tubes because the tapers and undercuts combined with compression rings frequently lead to the eyepiece being decentered or tilted.

I'd be happy to buy one or two to see if they're any good - if they had straight barrels - but the reply I got from Markus was ambiguous.

My other reservation remains the number of elements. Vixen achieved superb results with their SSW eyepieces with 2 fewer elements so its clear these APM ones aren't pushing any envelopes, optically, and the coatings would have to be something phenomenal to beat the SSWs (I have the 7, 10 and 14).

[bigjoe]

0

Good to know Wavy..SSWs have great reports ..but I only have some of Vixens Plossls. I like the 30mm.
I personally like the bevelled barrel, as on the newer Pan 19mms I have ..otherwise just straight would do me...I will talk to him or Wolfi at TS when Im ready to order about next month..Youd imagine Markus would not put his name on crap.
bigjoe.

[Wavytone]

Oh they aren't crap, that's for sure.

The big question is how the APM UFF 10 and 15 compare against say Vixen LVW 8 and 13, the Vixen SSW10 and 14, or the TV Nagler/Radian/Delos/Delite/Panoptic.

I'm thinking of ordering the 30mm and maybe the 18.

Here's another thought for you too... someone has recently revisited Dollond eyepieces (a cemented achro doublet) and concluded the image quality really is excellent if you can live with a 30 degree field of view. In particular the clarity and contrast are quite striking, and concluded that centuries ago refractor users really were able to push their scopes to the limits. It has had me scrabbling around tonight to find some optics I can cannibalise to make a Dollond, just to try. I either have to dismantle a 10mm LV (hmm...Kunama wants one) or a camera lens...

[Finski]

Thanks for the info guys!

What are different lengths good for? like a 10mm for planetary viewing and so on?

[Wavytone]

Given your scope is f/7.8 a useful range is from about 6mm (200X, high power) to a 25mm eyepiece (low power). It has a 1.25" focuser which rules out the larger 2" ones like the APM 30mm or Prostar 38mm 70-degree UWA.

[bigjoe]

Good review of APMs UFF 30MM over at Cloudy Nights.
bigjoe.

[bigjoe]

This sounds like the old adage that less elements is more in optical terms. An old Japanese 12.5 Kellner I had from Unitron had the sharpest and clearest image Ive ever seen on axis !
bigjoe

[Wavytone]

Joe there's even better - take the Kellner apart and use the doublet alone, plano side towards the telescope. The clarity and contrast will astound you, though the useful field of view is typically around 30 degrees.

An achromatic doublet used this way is actually a Dollond eyepiece and just goes to show that 18th century observers really did not lack good eyepieces. You want a really, really, fast doublet - say f/2 - and 12mm and 6mm focal lengths could be a bit hard to find.

I can safely say that a doublet used this way is better than the original Steinheil monocentric, and the contrast is almost as good as you would get from a spherical eyeiece (single element being a glass ball, with extremely limited field of view and virtually impossible to apply multilayer coatings). The bonus is the 30 degree FoV which, in its era, was first class. You can see why the RAS types swore by this eyepiece at the time, if they had one from a competent optician. No wonder the Steinheil was controversial in its day.

[bigjoe]

Sounds good will do..who cares about the field..were all obsessed with that aspect..Clarity first I say!
bigjoe

[Finski]

It comes with the 2" adapter, can/should I look at some 2" EPs also?

[Wavytone]

Sure, as per my previous post. But the maximum aperture inside the focuser will limit the useful field of view in low-power eyepieces. It will be a "bottleneck", in the literal sense, like sticking the narrow end of a coke-bottle into the focuser then trying to look through the bottom, as these big low power beasties have field stops in excess of 45mm - which is rather wider than your puny focuser.

Alternatively at some point you may decide to replace the focuser you have with a proper 2" one. Thus begins the slippery slope of upgrades, and at some point you will realise there is more merit in upgrading to a better scope rather than tinkering with what you have.

But IMHO resist the urge to upgrade bit-by-bit, it is ultimately futile when you are using consumer-grade gear. Best to live with what you have and its limitations, for a year or two. Learn the sky, and what there is to be seen. You will know when you are ready to upgrade and when that time arrives, flog the lot and buy a better scope - if you dare.

The only exception to that rule is when you have a scope that is quite special and you will keep for many, many years, possibly forever. My Santel MK91 is one such scope and deserves to be modernised carefully. The other scope to aspire to is a Questar, if you are lucky enough to have one these are treasures for life despite being vintage 1954 mechanically.

[wavelandscott]

I think that there is merit in this advice...It is easy and tempting to buy “upgrades” early in the hobby. Patience is a virtue and good gear (if taken care of) will last a lifetime. Take your time learn what you like by attending viewing nights and looking through other folks gear, then and only then (in my opinion) look to upgrade