widefield eyepiece for 9.25 SCT

[Tony_ (Tony)]

Does anyone know a good wide angle eyepiece that will give a flat field view in a 9.25 sct?
I currently use a 25mm WO swan - but the coma is terrible for most of the outer field of view. I was thinking of the 82d 18mm explore scientific - has anyone used this on an sct?
I don't do much visual work - but I want to get at least one decent eyepiece for when I do - preferably under $300.

Tony.

[brian nordstrom (As avatar)]

Hi Tony , I have a 2 inch Celestron 31mm , 82* Axiom LX and it works very , very well in my C9.25 .
Sharp almost to the edge and that's a l-oo-nn-gg way across .
I love mine its a great eyepiece.

These are (were , as they are not made anymore) a poor mans TelVue 31mm Nagler , almost as good , as huge and heavy as the telemangler at a cheaper price sorry its no help , but if you shop around you might find one 2nd hand .

Celestron now sell the Luminos? style that look a lot like the Axiom's but from what I have heard are not as good , made in another factory I am lead to believe.
But these come with some new Celestrons , especially the 23mm one so there are a few Luminos out there ?? worth a try ? .

Brian.

[Tony_ (Tony)]

Thanks Brian,

The 31mm axiom is (was) 1.3kgs! That's a big eyepiece.
The Luminos are around $200 from USA via ebay. I might see if I can find some reviews. It's also 82 degrees - I might check out the 19mm one. I wonder which is best out of these and explore scientific?

Regards,
Tony.

[astro744]

Are you looking for a 1.25" or 2" eyepiece?

There is a Tele Vue 41mm Panoptic in eyepiece classifieds at the moment with the tag "Make me an offer!".

This eyepiece has the maximum field stop diameter possible (46mm) in a 2" barrel giving you the widest true field of 1.1 deg. in a C9.25 and an apparent field of 68 degrees that is just about right without having to pan around.

You can also get a brand new Tele Vue 55mm Plossl for $299.00 at the moment which has the same field stop diameter but only 50 deg apparent field. This is the 'standard' eyepiece for maximum true field and also maximum exit pupil of 5.5mm, (4.1mm for the 41 Pan) at f10.

If you have only a 1.25" visual back then the eyepiece of choice is the Tele Vue 24mm Panoptic. This eyepiece has the maximum possible field stop (27mm) in a 1.25" barrel and will therefore give you a maximum true field of 0.66 deg with the C9.25. You also get the 68 deg apparent field that is easy on the eye. The 24mm Panoptic is currently $379.00 new locally. It is more than your $300 limit so you would have to decide if it is what you want to spend.

The 24 Pan is one of the most versatile eyepieces around and performs exceptionally in just about any telescope and also only uses 1.25" filters for lower cost (especially with narrowband filters). An alternative to the 24mm Panoptic is the Tele Vue 32mm Plossl which will give you the same maximum true field but only 50 deg. apparent field. These are $175.00 new locally.

If you have a 0.63 reducer/corrector you can use that in combination with the 24mm Pan or 32mm Plossl. Note you cannot combine the 0.63 reducer/corrector with a 2" diagonal and 41mm Pan as you will not get focus.

A note on the 41mm Panoptic. Due to the design of the eyepiece having an upper body that is flat on the bottom can cause some inconvenience when tightening the lock screw if the lock screw is small as is the case on some star diagonals. A diagonal with a larger lock screw with longer shaft resolves this issue. Another issue is weight as the eyepiece can cause the visual back to rotate due to the weight of the eyepiece so ensure the visual back is locked tightly. A third potential issue is that the eyepiece body may foul the focus knob of the SCT. A longer visual back or shorter focus knob solves this problem.

Note there are many variations to the SCT visual back configuration and some variations cause no issues whatsoever. I had all the issues above and solved them with a WO SCT-2" visual back and WO 2" diagonal, both of which have nice long and large lock screws. The weight issue depends a bit on ambient conditions and how well the threads bind on the night. I also try to keep the eyepiece in a vertical position no matter where the telescope is pointing to avoid rotation due to weight.

A final though is you could also consider the 35mm Panoptic which is $469.00 new but does at times come up for sale used as people move to the 31mm Nagler. This eyepiece is 2/3 the weight of the 41mm Panoptic and is a superb performer in an SCT.

[brian nordstrom (As avatar)]

I think you will find they are almost the same internally , same factory , just a different skin as per the client's specs/etc.
Yes Astro477, my 24 Panoptic is an awesome eyepiece , as is the 27mm .

Brian.

[AG Hybrid (Adrian)]

ES 30mm 82*

There's so much information on how well this eyepiece performs that I'm not even going to bother explaining why you should consider it.

[Camelopardalis (Dunk)]

If you're out of the City and have dark enough sky to support the low magnification, I'd suggest a 40mm Paragon...the Panoptic is supposed to be excellent also but I've not had the fortune to try one.

If you've got some sky glow then the ES82 30mm is a great eyepiece. I used to see a little coma towards the edges with my old C8, but the same would be true with any eyepiece pushing the wider field of view (including the 2 above).

Alternatively, you could try the Celestron reducer/flattener...it's supposed to clean up the view quite nicely for DSOs, and depending on what eyepieces you already have, you might not need another.

[brian nordstrom (As avatar)]

Thanks Dunk , I have one of these as well , don't use it much since I sold my Takahashi M210 and at 2415mm fl it performed very well , I will try it in my C9.25 and report back , yes a good eyepiece .

Brian.

Originally Posted by Camelopardalis

If you're out of the City and have dark enough sky to support the low magnification, I'd suggest a 40mm Paragon...the Panoptic is supposed to be excellent also but I've not had the fortune to try one.

If you've got some sky glow then the ES82 30mm is a great eyepiece. I used to see a little coma towards the edges with my old C8, but the same would be true with any eyepiece pushing the wider field of view (including the 2 above).

Alternatively, you could try the Celestron reducer/flattener...it's supposed to clean up the view quite nicely for DSOs, and depending on what eyepieces you already have, you might not need another.

[Gem (Grant)]

With my C9.25 I have used a variety of the EPs listed earlier in the thread (I have a 15mm Axiom, 24mm Pano, and a 32mm & 55mm TV Plossl). Although the Axiom is an ok EP - assuming your C9.25 is on a tracked mount, I would prefer a TV Plossl to the Axiom. If the budget allows, the Pano would be my option. The views are crisper than an Axiom and you don't need the extra FOV IMO if you are on a tracked mount. Otherwise, go the 32mm TB Plossl. Same FOV as the 24mm Pano. Any EP over 30mm is more for star hopping with a dob in my experience.
Personally I prefer a Pano to a Nagler for a tracked mount - but I know I will get plenty of opinions on that issue.
That said, I have over a dozen EPs covering the brands of Celestron (Axiom & Plossl), Sirius (Plossl), GSO (Plossl), Bintel (Plossl), TV (Plossl, Pano and Naglers) and seriously think TV is the most consistent - even in the Plossl range.

[Shano592 (Shane)]

I have the 41mm Panoptic, and it really is a magnificent view! At about 940g, it is certainly a heavyweight, but these sized scopes can take them easily.

However, my favourite eyepiece is my 21mm Ethos. It has 100 degree field of view ... you literally find yourself craning your neck to see the edge of the field of view.

[Tony_ (Tony)]

Thanks for your replies everyone!
The ethos would be nice - but at $999??

I do mostly imaging but it would be good to have a few decent eyepieces.
I might go for a 82D 18mm to start with or maybe a 31mm and get a celestron reducer (I've currently got a Hirsch one but it isn't very good - maybe it will work with a better eyepiece?) That should give me enough combinations.

Regards,
Tony.

[mental4astro (Alexander)]

There are a couple eyepiece lines that Celestron currently makes that are designed for use in SCT's. In Schmidt Cassegrains they work brilliantly, but placed in other telescope optical designs, like a Newt, and they are poor performers. No flaw in the eyepiece, just not an optical match. This is like the Baader Hyperions - great in SCT's (for which they are designed for) but poor in any other scope.

These are the Ultima LX line and the Luminos. I have the 8mm and 13mm Ultima LX eyepieces. Brilliant in my C8. The 8mm is particularly easy on the eye - I love using it while doing my Lunar sketches as it gives me the least amount of eyestrain. But both are useless in my fast Newtonians.

Nothing wrong with the Luminos either. Yes they are made in a different factory from the discontinued Axiom, but they are a different design to the Axiom - nothing to do with the manufacturer being different. Some of the old Axiom LX line were great across different types of scopes. The 31mm and 23mm are really good in Newt's. But Celestron does not make large Newt's anymore. They can concentrate on making their premium line of eyepieces for SCT's that way.

We expect every single eyepiece to perform exactly the same from a refractor to Newtonian to SCT to Mak. But we forget that these are all distinct optical designs, all with different shaped focal planes, and with a great range of focal ratios between each adding to the complexity. It is also the same for eyepieces that they will also be differences between them, and different ones will be best suited to different optical systems of scope's. Few are the designs that will do well in ALL systems, and even within an eyepiece line, there will be performance difference - there has to be. Unfortunately manufactures DON'T tell us these things, for fear that their products would be seen as faulty. We as consumers get it in the neck when we purchase an eyepiece, stick it in a scope, and are disappointed with the resulting image. Just as bad though, we then proceed to write off this eyepiece as crap, when we haven't matched the EP to the scope.

The Ultima LX line can be had from the States from around US$100. If all you have is an SCT, then these are a good eyepiece for your scope. You will find the 32mm will do well in your C9.25.

Focal reducers are designed for photographic applications. They do not do well with eyepieces as a whole (there will be exceptions). Don't forget, reducer-come-correctors will by definition alter the shape of the focal plane of the outgoing light cone from the initial one, to suit an SCT with its inherent aberrations. Eyepieces are not designed to handle this change, so the resulting image is poor - nothing to do with having a crap eyepiece. Your Hirsch reducer is the exact same one that Celestron and Meade sell for five times the price! Nothing wrong with the reducer. Everything wrong with what you are expecting the reducer to do for you.

Mental.

[astro744]

Here is a low cost alternative you may consider; 1rpd 30mm/80deg. http://www.astrobuffet.com/ab/30mm.html

I have one of these that permanently sits in my ED80 case. I bought it for my Newtonian but it is a poor performer in that but not too bad with the ED80. I have not used it in my C9.25 but will try next clear night.

It was this eyepiece that introduced me to Tele Vue and I have never looked back such was it's performance in a Newtonian (significant field curvature in outer 30%). In a Newtonian it simply cannot hold up to a 31 Nagler or 41 Panoptic but I have not tried it in my C9.25 as I bought the SCT after my Tele Vue eyepieces.

As was already mentioned by another user, it is the eyepiece and telescope combination that gives the final result and what eyepiece works for one telescope may not for another. However I must say, Tele Vue work very well for all and if you ever are getting other designs of telescopes, you cannot go wrong with what Tele Vue have to offer. The most you will ever want to add is a Paracorr on a fast Newt, but some people are more annoyed by coma than others and it is primary mirror coma in its purest form, not astigmatism and other aberrations caused by poor eyepieces.

[Renato1 (Renato)]

I guess it all depends on what you want to use the eyepiece for, and whether you like using a 1.25" or 2" star diagonal. If you want it for faint DSOs, you'd want an eyepiece with a a 2mm exit pupil - meaning a 20mm eyepiece plus or minus a millimeter (or two, perhaps).

The choices are somewhat limited for a 1.25" diagonal. I used a 20mm Erfle for years to look at around 1500 DSOs in Sky Atlas 2000, though I recently switched to an inexpensive but very good 19mm flat field eyepiece with 65 degree field (sold under various names e.g. Orion Edge on/BST/Smart Astronomy/ Orbinar). I also have an 18mm Meade Series 5000 Ultrawide which fits in the 1.25" diagonal - magnificent views - but is very heavy and I have to really tighten the thumbscrew in the diagonal hard (it cost me around $160 new on US Ebay).

But if you like using a 2" diagonal with heavy eyepieces, then you have heaps of choices. I find the 2" diagonal awkward on an SCT, (though I have two of them) and mainly use it occasionally with a cheapish ultrawide angle 30mm eyepiece or wide angle 40mm eyepiece for the visual treat of sweeping around the Milky Way.
Regards,
Renato

[PeterHA (Peter)]

I have got the ES 24 mm 68 degree and it is visually like an extension to the Delos range. ER just good enough to use with glasses and optically like my 17.3 mm Delos, has the max field for a 1.25" barrel.

[Camelopardalis (Dunk)]

IMO 2" is the only way to go for pushing the widest FOV you can get...at maximum, the 2" eyepiece can offer up to 3x the field area compared to that of the 1.25" barrel.

But they're not all heavy, just many are. I've mentioned the Paragon before which is about 500g, and the Baader Aspheric 36mm is maybe slightly less (and slightly less FOV).

[uwahl (Ulrich)]

I came across this thread on doing a search. I am interested in having a very long FL eyepiece (50 or 55mm) for my 10" Meade F8 ACF. I had been told that at these focal lengths you start to see the shadow of the secondary in the middle of the field of view so have been reluctant to invest.
I see that some of you use 55 mm eyepieces in F10 SCT's with no issues and would be most interested in the views of experienced members re the above.

[Camelopardalis (Dunk)]

It depends how dark your sky is and how much you tolerate sky glow. In a suburban area, I wouldn't bother...at 45x you're likely to be overwhelmed by artificial lighting obscuring the fainter details you might otherwise gain from using the larger exit pupil.

[Tony_ (Tony)]

I bought a 18 mm 82d explore scientific from another IIS member.

It is much better than the 72d 25mm WO SWAN that I have been using. The stars are rounder for close to 90% of the view and much less pronounced coma towards the edge - not seagulls like the WO.

It seems to have better contrast and gives more details of GCs and Nebs. I will consider the ES 30mm next. I wanted a wide AFOV more than the wide actual field. The higher magnification combined with the wider field gives great views of the larger globular clusters especially 5139, 6752, 6397, m22, m55 etc.