79 replies to this topic

[Joe Cepleur]

Back in the fall, I received two exceptional telescopes, the first I have ever had that would accept 2-inch eyepieces. I have never owned any 2-inch eyepieces and have been biding my time, waiting to buy them when I could better afford good ones. But, life is passing by during the wait, and now with the trade war and tariffs, I am concerned that costs will rise even as inventories drop on eyepieces of all grades. I am therefore considering buying an inexpensive set of 2-inch eyepieces now, with the hope that I could buy better ones later. 

 

I am hoping that objective comments may be possible about what I might expect from low-priced brands such as Svbony, Astromania, or GSO, as I have not had the opportunity to try them, let alone to compare them side-by-side with premium brands. Might they be a happy enough purchase for now, or such a disappointment that I may as well not have bought them? The attraction would be their wider fields of view, but what would be the overall quality of the images?

 

The first telescope is a 6-inch, f/4 Dob with an exceptional mirror that had served as a test mirror for my club’s founder’s optical engineering company. After he retired, it had been installed in an astrograph. More recently, that astrograph was converted to a mini-Dob, so that one of our more intrepid members could haul it for visual observing into a dark skies wilderness on a toboggan in winter. It was passed to me when the intrepid adventurer was culling his herd and I needed a lightweight telescope that I could easily lift.

 

The second is a classic, 6-inch f/10 achromatic Jaegers refractor from the early 1970s with a Unitron Superfocuser and an adapter for 2-inch eyepieces. One might argue that it is no AstroPhysics, but I would counter that I’m okay with achromats for visual use, and this is likely as fine a large refractor as I shall ever have. The contrast in this telescope is mind-boggling!

 

My personal lack of 2-inch eyepieces has not prevented using these telescopes. When friends are not loaning the finest eyepieces and coma correctors for the mini-Dob at star parties, my existing crop of 1.25-inch eyepieces certainly works. The Jaegers is such an intriguing telescope that, on the few occasions when I have used it (it’s a monster to move!), it always attracts 2-inch loaner eyepieces.

 

I have looked on Astromart and Cloudy Nights Classifieds, but find that good quality eyepieces sell for respectable prices even when used. That has led me to wonder about these lower-priced, new eyepieces. Adding to the cost would be an inexpensive coma corrector and an inexpensive Barlow, possibly one of those four-element models that attempt to emulate TeleVue Powermates. An entire set could be purchased for the price of one or two high-end eyepieces, but I know that the quality would not be the same. I would not buy any 2-inch eyepieces that would not potentially improve the field of view over my current 1.25-inch eyepieces, certainly none shorter than 20mm.

[Mike W]

30mm UFF by APM, SVbony, Celestron, etc.

[sevenofnine]

Another to consider from our sponsor. Highly forum recommended 

 

https://astronomics....a-82-2-eyepiece.

[wkight]

I've been very satisfied with the Explore Scientific 28mm 68 degree eyepiece, as well as the Apertura (GSO) 30mm ultrawide.  

[Joe Cepleur]

Another to consider from our sponsor. Highly forum recommended 

 

https://astronomics....a-82-2-eyepiece.

That one looks good, thanks, except that at 12mm, it lacks the eye relief that I prefer for use with eyeglasses. 

[Bob4BVM]

Contrary to much of what you see here, you do not need to spend a fortune for good 2" WF EP's. This is especially true for your F10 Jaegers, which is very easy on EP's.

I'd challenge most people to detect any appreciable difference in a $600 Televue and a $150 AT or APM EP of similar specs in that scope.

 

BTW, congrat's on the Jaegers. I had a 6F15 so i know what you mean about hauling it out, but it's worth it every time   I eventually folded it in half, much easier now.

 

CS
Bob

Edited by Bob4BVM, 06 May 2025 - 03:13 PM.

[SeattleScott]

F4 and F10 are two very different animals. The 30UFF (available under many different brands) is the cheapest that will perform well at F4. It should cost around $200. You could get something for half that price that would work fine with the refractor, but it would be a mess in the reflector.

A 30mm will provide a very bright background sky at F4. Honestly you almost need two 2” eyepieces. One for the F4 and one for the F10. I use an ES 24/82 at F4 or F4.8 and a 42mm LVW at F8+. A 30UFF would kind of split the difference. Exit pupil is a bit large at F4 and TFOV a bit small for the refractor. But it would be serviceable in either.

A 20mm hyperwide is another option, especially for the Dob. But the “affordable” ones (that only cost $300 or so) aren’t the best in terms of edge correction at F4, and the Ethos is massively expensive, and would really mess with balance on the little Dob.

Understand what is involved with configuring a coma corrector. Basically you have to make your eyepieces parfocal. So plan on extension tubes and parfocal rings and a good deal of trial and error. Obviously parfocal eyepieces are a plus. And then there is the stack, and weight, of hanging a coma corrector with a 24mm 82 or 20mm 100 sticking out of it, protruding from the mini Dob. People complain Dobs look like WWI mortars. But you wouldn’t have that problem. Your Dob wouldn’t look like anything! It would be the weirdest looking telescope most novice stargazers have ever seen. You would have a line of people just curious about what the heck it is. And you would need significant counterweight for balance.

Ok so now what I would do:
38mm Agena SWA (for the refractor)
20mm Long Perng (for both)
The Long Perng is 80 AFOV with good ER and great edge correction. My 14mm is pretty close to parfocal with my 1.25” eyepieces, which should make configuring a coma corrector easier. It isn’t particularly expensive for a premium 2” eyepiece. The downside: it is only somewhat wider view than a 1.25” max FOV eyepiece (maybe 10% wider).

Another potential option: the 20mm Houdini. This would go a bit wider, and eliminate the need (and hassle, and stack) of a coma corrector.

[Augustus]

I would get a 30mm UFF or the new 20mm Houdini and call it a day, it will work well enough in both, and isn't too heavy and tip over the 6" f/4. Exit pupil isn't that bad

Your widest field 1.25" eyepiece is the same FOV as a 20mm 80-degree and while a 30mm UFF doesn't max out the field in the Dob anything more is gonna have coma and be a very heavy eyepiece anyway. Leaving an MPCC screwed on isn't that expensive though and neither is just getting the Houdini with built in coma correction

 

Understand what is involved with configuring a coma corrector. Basically you have to make your eyepieces parfocal. So plan on extension tubes and parfocal rings and a good deal of trial and error. Obviously parfocal eyepieces are a plus. And then there is the stack, and weight, of hanging a coma corrector with a 24mm 82 or 20mm 100 sticking out of it, protruding from the mini Dob. People complain Dobs look like WWI mortars. But you wouldn’t have that problem. Your Dob wouldn’t look like anything! It would be the weirdest looking telescope most novice stargazers have ever seen. You would have a line of people just curious about what the heck it is. And you would need significant counterweight for balance.

MPCC just screws onto eyepiece, HRCC and Paracorr are adjustable

And I have such a scope, granted I use it on a GEM too

[k5apl]

You might want to keep in mind that really wide field eyepieces require us to  move our heads around to see the entire fov.  That is why I buy approx 65-70 degree eyepieces.  And the same works for me with binoviewers.  Just

food for thought.  Have fun with those two nice scopes.

 

Wes

[Starman1]

Back in the fall, I received two exceptional telescopes, the first I have ever had that would accept 2-inch eyepieces. I have never owned any 2-inch eyepieces and have been biding my time, waiting to buy them when I could better afford good ones. But, life is passing by during the wait, and now with the trade war and tariffs, I am concerned that costs will rise even as inventories drop on eyepieces of all grades. I am therefore considering buying an inexpensive set of 2-inch eyepieces now, with the hope that I could buy better ones later. 

 

I am hoping that objective comments may be possible about what I might expect from low-priced brands such as Svbony, Astromania, or GSO, as I have not had the opportunity to try them, let alone to compare them side-by-side with premium brands. Might they be a happy enough purchase for now, or such a disappointment that I may as well not have bought them? The attraction would be their wider fields of view, but what would be the overall quality of the images?

 

The first telescope is a 6-inch, f/4 Dob with an exceptional mirror that had served as a test mirror for my club’s founder’s optical engineering company. After he retired, it had been installed in an astrograph. More recently, that astrograph was converted to a mini-Dob, so that one of our more intrepid members could haul it for visual observing into a dark skies wilderness on a toboggan in winter. It was passed to me when the intrepid adventurer was culling his herd and I needed a lightweight telescope that I could easily lift.

 

The second is a classic, 6-inch f/10 achromatic Jaegers refractor from the early 1970s with a Unitron Superfocuser and an adapter for 2-inch eyepieces. One might argue that it is no AstroPhysics, but I would counter that I’m okay with achromats for visual use, and this is likely as fine a large refractor as I shall ever have. The contrast in this telescope is mind-boggling!

 

My personal lack of 2-inch eyepieces has not prevented using these telescopes. When friends are not loaning the finest eyepieces and coma correctors for the mini-Dob at star parties, my existing crop of 1.25-inch eyepieces certainly works. The Jaegers is such an intriguing telescope that, on the few occasions when I have used it (it’s a monster to move!), it always attracts 2-inch loaner eyepieces.

 

I have looked on Astromart and Cloudy Nights Classifieds, but find that good quality eyepieces sell for respectable prices even when used. That has led me to wonder about these lower-priced, new eyepieces. Adding to the cost would be an inexpensive coma corrector and an inexpensive Barlow, possibly one of those four-element models that attempt to emulate TeleVue Powermates. An entire set could be purchased for the price of one or two high-end eyepieces, but I know that the quality would not be the same. I would not buy any 2-inch eyepieces that would not potentially improve the field of view over my current 1.25-inch eyepieces, certainly none shorter than 20mm.

30mm Ultra Flat Field 70°, sold under labels Altair Astro UFF, APM UFF, Celestron Ultima Edge, Meade UHD, Sky Rover UFF, Stellalyra UFF, Stellavue UFF, Tecnosky UFF,  

28mm (actually 28.5mm) 82° sold under labels Astrotech UWA, Sky Rover UWA, Stellarvue UWA, Tecnosky UWA, Telescope Service UWA, 

22mm 70° SWA, sold under labels Astromania SWA, Arturus Ebony, Omegon Redline, SkyWatcher SWA, Tecnosky Superwide HD, Telescope Service Expanse ED

 

All are less expense than premium eyepieces, but all deliver a lot better performance than their price classes.  They are standouts in inexpensive 2" eyepieces.

 

A little up from that price range, but worthy of note: 20mm XWA 100°(sold under many labels).

The 20mm Houdini, mentioned earlier, would be an eyepieces for the f/4 reflector, but not the other.

Edited by Starman1, 06 May 2025 - 04:05 PM.

[vtornado]

APM UFF 30mm is excellent at F/5  and around $200.00.

I've heard the AT 28/80 is very good too, but I have not had a look through one.

 

Orion Q70 and it's ilk  are around $100.00 but the outer field  starting at around 20 degrees from center shows astigmatism at f/5.  (Stars look like streaks) I'm sure it would be worse at f/4.  How deep are you pockets?  How picky are you about the view?

Edited by vtornado, 06 May 2025 - 04:26 PM.

[Jay_Reynolds_Freeman]

At f/4, you probably don't need two-inch eyepieces unless the pupils of your eyes dilate to more than 6 mm and you observe in extremely dark sky. A 20 mm Erfle in a 1.25-inch barrel, used in your six-inch f/4, would give a magnification of 30, a 5 mm exit pupil, and a field of view over two degrees wide. Such an eyepiece would be excellent as an aid for finding things, and might be optimal for observing large low-contrast objects in less than very dark sky. Possibly you already have a similar eyepiece that is suitable. If you do have large eye pupils and dark sky, then a longer focal-length eyepiece in a two-inch barrel might be useful, but again -- if you are looking for inexpensive units -- consider a used Erfle or Konig. At f/4, Erfles and Konigs will show astigmatism from the eyepiece and coma from the primary mirror, but those aberrations might be an acceptable tradeoff for low cost.

 

At f/10, two-inch barrel eyepieces of even relatively simple design would get you a wider field than 1.25-inch barrel units, for any focal length greater than roughly 20 or 25 mm. The considerations I mentioned in the first paragraph suggest that the most important two-inch eyepiece you might want would have a focal length of 40 to 50 mm. There is no need for a particularly fancy design, since f/10 is quite forgiving of eyepiece aberrations and older designs will make good use of the field of view that a two-inch barrel provides. Plossls would work fine, or for slightly wider fields, again consider a used Erfle, Konig or similar type. At f/10, the innate astigmatism of these latter eyepieces will be much less objectionable than at f/4.

 

Continuing at f/10, once you have an eyepiece of focal length 40 to 50 mm, you might at some time find yourself wanting another two-inch barrel unit with a focal length of 30 to 35 mm, but that purchase can probably wait a while, since the longer focal-length two-inch-barrel unit will work well for finding things. You may already have 1.25-inch barrel eyepieces in this focal length range, and if you don't, you might save a little money by buying one with a 1.25-inch barrel and a very simple design (Plossl, orthoscopic, modified achromatic) forgetting the wide-field aspect but getting the right magnification.

 

Thus you may find that the total number of low-cost two-inch-barrel eyepieces you need at the moment is exactly one -- a 40 to 50 mm Plossl, Erfle or Konig.

 

 

Clear sky ...

[T1R2]

I also believe a 38/ 70* 2" for the F10 refractor would be a good choice, the 38/70* would give a slightly wider tfov as the 50mm/ 52* Erfle design (about 1.7* vs 1.75*)  like the GSO Superview / TS Optik, but with a little more magnification/ better resolution,  but they're both a decent price so you might end up with both of them for the refractor. 

 

A 1.7* tfov is just about perfect for bouncing around to multiple showpiece objects (M39, M27, M13, M8 etc, except for the largest like M45 and some extended nebs like the North American Neb.)  without having to change eps unless you want a more detailed view with higher power.

[GGK]

The observer’s eye pupil diameter might matter at f/4.

At f/4, a 30mm eyepiece creates a 7.5mm exit pupil. If the observer’s eye pupil is only 6mm, for example, the effective aperture seen is only 80% of actual aperture, or 4.8” in the 6” DOB. I don’t have a DOB, so don’t know when the secondary mirror’s shadow becomes visible with an oversized exit pupil.

I do use f/4 refractors, though, and stay at or below a 25mm eyepiece unless I want the larger field stop / wider true field of the longer focal length eyepiece. Losing significant aperture is noticeable. For this reason a shorter focal length and larger apparent field for the larger field stop / true field is a good direction. The 20mm XWA is already mentioned, and does well enough in my f/4 refractors that I don’t hesitate to recommend it at that price point.

Of course, if the observer has a 7.5mm or greater eye pupil diameter, then none of this matters and the 30mm UFF is a great option too at that price point. My eye pupil is just over 6mm, and I always consider the impact of an oversized exit pupil on effective aperture with long focal length eyepieces.

Congratulations on your scopes. I’d love looking through the 6” f/10.

Gary

[SeattleScott]

30mm Ultra Flat Field 70°, sold under labels Altair Astro UFF, APM UFF, Celestron Ultima Edge, Meade UHD, Sky Rover UFF, Stellalyra UFF, Stellavue UFF, Tecnosky UFF,
28mm (actually 28.5mm) 82° sold under labels Astrotech UWA, Sky Rover UWA, Stellarvue UWA, Tecnosky UWA, Telescope Service UWA,
22mm 70° SWA, sold under labels Astromania SWA, Arturus Ebony, Omegon Redline, SkyWatcher SWA, Tecnosky Superwide HD, Telescope Service Expanse ED

All are less expense than premium eyepieces, but all deliver a lot better performance than their price classes. They are standouts in inexpensive 2" eyepieces.

A little up from that price range, but worthy of note: 20mm XWA 100°(sold under many labels).
The 20mm Houdini, mentioned earlier, would be an eyepieces for the f/4 reflector, but not the other.

Reports coming in suggest the Houdini does just fine in a slow refractor. Perhaps expensive for an ultrawide for a F10 scope, but if getting it for the mini Dob, it should be fine in the refractor.

I get the impression there is a small price to pay for coma correction, and it might not be quite as crisp as premium brands that are similarly priced. Which could be a drawback for the refractor. But again, people seem to like it in their Tak Apos, so I guess it should be fine.

[Procyon]

You might want to keep in mind that really wide field eyepieces require us to  move our heads around to see the entire fov.  That is why I buy approx 65-70 degree eyepieces.  And the same works for me with binoviewers.  Just

food for thought.  Have fun with those two nice scopes.

 

Wes

I don't move my head around when I use a 25mm ES 100, 20mm TS Optics XWA (Twist Top), 17mm Nikon HW 102º, 17mm & 12mm ES 92's. You can move your eye around if you want, but not the head on these ones. Or any Nagler 82º type I've had.

 

For these three I do need to move my head around a bit, some more than the other: 31.5mm Antares 90º (Very little, but this view is endless), 9mm WO XWA (A bit too much) and 5mm WO XWA (All the time, both are Twist Tops).

Edited by Procyon, 06 May 2025 - 11:07 PM.

[GolgafrinchanB]

Some low cost eyepieces are terrible, but there are plenty of highly recommended ones that do great. I wrote on here recently comparing the 9mm svbony "goldline" to an 8mm televue delos https://www.cloudyni...m-delos-tested/ with your question in mind. The result was basically AFOV and clarity near the edge of the FOV being the main differences.

[Joe Cepleur]

Wow! Thank you all. So many fine thoughts! Cloudy Nights never ceases to amaze me, despite that I have been among those responding to many questions over the years. 

 

Obviously, the two telescopes are so different that finding shared eyepieces is not impossible, but a bit comic. It's as though I reported having two pets, a dog and a parrot, and wanted help finding shared bedding, toys, and food for them. 

 

One thing is readily apparent: When I am ready to spend what I would consider to be "real money," there are lots of good eyepieces available in the few hundred dollar range. 

 

I do not know the size of my dilated pupil at night. How would I measure it? I can say that despite my being in the youth of old age (early toward mid-60s), I have excellent night vision. It seems less likely that that would be due to magical sensitivity of my rods and cones, so having unusually large dark-adapted pupils is a possibility. I can also say that I am typically more troubled by the shadow of a secondary mirror than are most of my friends, again suggesting large pupils. 

 

Just living with 1.25" eyepieces for the mini-Dob would certainly solve all problems of additional expense! I had considered that, but was wanting the wider fields of view possible with 2" eyepieces. Because coma worsens the farther one looks from the center of the field, by sticking with 1.25-inch eyepieces, I would be avoiding the wider extension of the field where a coma corrector would principally have been needed. A double savings there: no new eyepieces, and no coma corrector. 

 

I had planned to avoid super-wide eyepieces, because I dislike them. While I appreciate the coolness of the porthole view and admire the accomplishments of the optical engineers who can create it, I find them awkward to use with my eyeglasses and dislike having to search the periphery with a turned head or turned eyes to see the entire field. As a bonus, my preference lowers the potential cost of eyepieces. 

 

My sense of "low priced" is notably lower than may be realistic for the mini-Dob, or may even be considered honorable among knowledgeable astronomers. Would an eyepiece such as this one be an utter waste of money for the mini-Dob, especially if used without a coma corrector, or would it at least aid in finding objects? 26mm would create an exit pupil of 6.5mm in the 6" f/4. I can think of vendors whose descriptions I trust, but am hesitant to presume the quality of information presented on Amazon.com. But, for US $53: 

 

SVBONY SV154 Telescope Eyepiece 2 inch Super Wide Angle Eyepiece 70 Degree 26mm 

 

If that eyepiece might be helpful when combined with my current collection of 1.25-inch eyepieces, that and a 50mm or 56mm Plossl for the 6" f/10 Jaergers refractor might be all I would need for now. Or, would I be better to not get so long a Plossl for the refractor? 

 

GolgafrinchanB, thank you to the link to your review of the Svbony Gold Line. Lots to learn there. For now, I was only considering buying eyepieces of longer focal length, yet great to see someone seriously studying the gap between super-modest and super-premium eyepieces.

 

The 20mm Houdini sounds brilliant! Perhaps it will start a trend in the design of eyepieces? Are there any advantages to having a separate coma corrector? There were mild critiques of the Houdini's sharpness at the center of the field. 

 

I had not known how to configure a coma corrector, but because my eyepieces all require different amounts of futzing regarding how deeply they ride in the focuser when able to reach focus, I had thought about getting spacers anyway. The question then would be whether those spacers would interfere when using the eyepieces in other telescopes. 

[Starman1]

I do not know the size of my dilated pupil at night. How would I measure it? I can say that despite my being in the youth of old age (early toward mid-60s), I have excellent night vision. It seems less likely that that would be due to magical sensitivity of my rods and cones, so having unusually large dark-adapted pupils is a possibility. I can also say that I am typically more troubled by the shadow of a secondary mirror than are most of my friends, again suggesting large pupils. 

 

Actually, sensitivity to the secondary shadow is a sign of smaller pupils.  That shadow becomes a smaller % of large pupils and so is less noticeable.

 

Just living with 1.25" eyepieces for the mini-Dob would certainly solve all problems of additional expense! I had considered that, but was wanting the wider fields of view possible with 2" eyepieces. Because coma worsens the farther one looks from the center of the field, by sticking with 1.25-inch eyepieces, I would be avoiding the wider extension of the field where a coma corrector would principally have been needed. A double savings there: no new eyepieces, and no coma corrector. 

 

The visibility of coma is directly related to the size of the APPARENT field, so is more visible in wider eyepieces, regardless of focal length.  Sticking to 1.25" eyepieces does not guarantee being less bothered by coma, since many 100-110° eyepieces are 1.25" (just not in long focal lengths).

 

I had planned to avoid super-wide eyepieces, because I dislike them. While I appreciate the coolness of the porthole view and admire the accomplishments of the optical engineers who can create it, I find them awkward to use with my eyeglasses and dislike having to search the periphery with a turned head or turned eyes to see the entire field. As a bonus, my preference lowers the potential cost of eyepieces. 

 

Unless the wider field eyepieces are designed for glasses use, like Baader Morpheus or Tele Vue Type 4 or Type 7 Naglers or Long Perng 80°.

 

My sense of "low priced" is notably lower than may be realistic for the mini-Dob, or may even be considered honorable among knowledgeable astronomers. Would an eyepiece such as this one be an utter waste of money for the mini-Dob, especially if used without a coma corrector, or would it at least aid in finding objects? 26mm would create an exit pupil of 6.5mm in the 6" f/4. I can think of vendors whose descriptions I trust, but am hesitant to presume the quality of information presented on Amazon.com. But, for US $53: 

 

SVBONY SV154 Telescope Eyepiece 2 inch Super Wide Angle Eyepiece 70 Degree 26mm 

 

This eyepiece has significant astigmatism in the outer field. You can do better.

 

If that eyepiece might be helpful when combined with my current collection of 1.25-inch eyepieces, that and a 50mm or 56mm Plossl for the 6" f/10 Jaergers refractor might be all I would need for now. Or, would I be better to not get so long a Plossl for the refractor? 

 

If you want a widest-possible true field in the scope, a 55-56mm Plössl or a 40-41mm 68° eyepiece both make sense, and both would be glasses-compatible.

 

The 20mm Houdini sounds brilliant! Perhaps it will start a trend in the design of eyepieces?

 

The designer is coming out with more focal lengths over time.  12mm and 7mm are next, and they are 1.25".

 

Are there any advantages to having a separate coma corrector? 

 

Yes, the coma corrector essentially parfocalizes all your eyepieces so near-zero focuser movement is necessary, and people who view without glasses can optimize coma correction for their eyes by adjusting the distance between eyepiece and coma corrector rather than focusing with the focuser and moving the CC away from its optimum position in the light cone.

 

I had not known how to configure a coma corrector, but because my eyepieces all require different amounts of futzing regarding how deeply they ride in the focuser when able to reach focus, I had thought about getting spacers anyway. The question then would be whether those spacers would interfere when using the eyepieces in other telescopes. 

 

Not at all.  Once a set of eyepieces is parfocalized for one scope, it is parfocalized in all scopes.

[kasprowy]

"SVBONY SV154 Telescope Eyepiece 2 inch Super Wide Angle Eyepiece 70 Degree 26mm

This eyepiece has significant astigmatism in the outer field. You can do better."

 

I use this with a Dioptrix in an ST120. It works really well. 

[Jay_Reynolds_Freeman]

But, for US $53: 

 

SVBONY SV154 Telescope Eyepiece 2 inch Super Wide Angle Eyepiece 70 Degree 26mm

A 26 mm focal length eyepiece in your f/4 Dobson would produce a 6.5 mm exit pupil, which might be too large. "Try before you buy" is perhaps good advice, and you can use any (borrowed) 26 mm eyepiece, or one of nearly that focal length, to investigate the exit-pupil issue.

 

Clear sky ...

[SeattleScott]

It was pointed out that the specific coma corrector you were looking at actually screws onto the eyepiece. This eliminates the need to make eyepieces parfocal. However it means screwing it on and off each time you swap eyepieces.

There is a reason why people pay hundreds for a Paracorr. It’s expensive, but it’s plug and play.

That particular eyepiece would be a mess at F4. If you want wide AFOV at F4, in 2” format, with respectable edge correction, you just have to put blinders on and forget that $50 eyepieces even exist. (That being said, it does just fine at F10.)

If you don’t like more than about 68 AFOV anyway, you might as well just use a 24mm SWA in 1.25” format for the newt. The 30mm 70 AFOV is an option too if you can manage with the large exit pupil. As pointed out, if you are more sensitive to secondary shadow, that suggests your eye doesn’t dilate as much as others (or you are just more observant). But you could do a simple test. Put a 30-32 Plossl in the Dob and see if you notice secondary shadow. If you do, then don’t bother getting the 30mm 70 AFOV. If not, the 30UFF would work for you (for now).

Edited by SeattleScott, 07 May 2025 - 01:02 PM.

[SeattleScott]

"SVBONY SV154 Telescope Eyepiece 2 inch Super Wide Angle Eyepiece 70 Degree 26mm
This eyepiece has significant astigmatism in the outer field. You can do better."

I use this with a Dioptrix in an ST120. It works really well.

That’s also F5 not F4, and there is no assumption of sharp stars near the edge of the field due to the field curvature of the scope.

Now opinions will vary and some people will like an eyepiece that isn’t normally recommended. Some people will pay extra for good edge correction, while others will buy budget eyepieces and not let fuzzy edges bother them. But certainly the eyepiece isn’t typically recommended at F4.

[Starman1]

"SVBONY SV154 Telescope Eyepiece 2 inch Super Wide Angle Eyepiece 70 Degree 26mm

This eyepiece has significant astigmatism in the outer field. You can do better."

 

I use this with a DioptRx in an ST120. It works really well. 

Is your ST the f/5 version?

I used this eyepiece in an f/7 triplet and the outer 50% of the field was poor.

I used the eyepiece labeled as a Meade Q70 26mm.  Same eyepiece.

[kasprowy]

Is your ST the f/5 version?

I used this eyepiece in an f/7 triplet and the outer 50% of the field was poor.

I used the eyepiece labeled as a Meade Q70 26mm.  Same eyepiece.

The f/5 but the edges don't bother me. Couple nights ago I had the Moon occulting a star, with Mars and the Beehive in the same field of view. My eyes only focus on the center. I can move my scope a tad, or spend a lot more to just move my eye (or head). The original thread was "Expectations for Low Priced Eyepieces" but we've veered into Naglers, Houdinis, various 100/110s, and APM UFF, the cheapest of which are over $200. I'm just saying for ~$50 it gives me a pretty good view. If you need flat edge to edge then you need to spend 4 to 10 times more.