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WO Swan 33mm at F/6

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#1 CollinofAlabama

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Posted 18 November 2019 - 02:58 AM

Folks, I’m aware the SWAN series are not so hot at F/5, but I have a dob and refractor at F/6.  What’s your experience with the 33mm Swan (supposedly the best edge correction of the 2”-ers) at F/6?



#2 CollinofAlabama

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Posted 19 November 2019 - 01:48 AM

Hey, don’t everybody respond all at once.  I mean, there must be someone that’s put one in his F/6 scope in the last 16 years, ya think?



#3 F.Meiresonne

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Posted 19 November 2019 - 02:01 AM

Years ago a fellow observer got a Swan. I've tried in out in my scopes, ok at F/5 and not F/6  but from what I have seen I would not advice it , not even at F/6.

 

Maybe have a look at ES eyepieces, or TS expanse 30 mm,


Edited by F.Meiresonne, 19 November 2019 - 06:31 AM.

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#4 russell23

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Posted 19 November 2019 - 04:03 AM

Well it is basically the same as the 32mm Orion Q70 and that was not very good in a 120mm f/8.3 refractor.  If you want passable edge performance there are better options, but they cost more.  


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#5 havasman

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Posted 19 November 2019 - 09:15 AM

Based on my earlier experiences with the 25 and 40mm SWAN's at f4.7 and f7, the optical performance will be quite compromised in the outer field. Not the outer edge of the field but the outer third.

 

But it may still be the most comfortable ep in your kit (1st class eyecup) and the color balance will be a bit to the "white" side (good for me.) It'll be lightweight. It seems inexpensive when you run the numbers against other ep's in it's focal length/AFOV class.

 

But in the end it's all about the optical performance and I would not recommend it at all at f6. 


Edited by havasman, 19 November 2019 - 09:16 AM.

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#6 Miranda2525

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Posted 19 November 2019 - 09:19 AM

Folks, I’m aware the SWAN series are not so hot at F/5, but I have a dob and refractor at F/6.  What’s your experience with the 33mm Swan (supposedly the best edge correction of the 2”-ers) at F/6?

If you can put up with off axis astigmatism.....



#7 cimar

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Posted 19 November 2019 - 10:24 AM

Hi, 

a 31mm Baader Aspheric is much better according to my experience. I use and like this eyepiece with my f/5 scopes.



#8 beatlejuice

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Posted 19 November 2019 - 10:28 AM

Here is an old review of the whole line.  For what it is worth his review of the 40 pretty much matches my experience with it in my 120 f/8.3 refractor.

 

Eric


Edited by beatlejuice, 19 November 2019 - 10:37 AM.


#9 CollinofAlabama

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Posted 19 November 2019 - 11:47 AM

Okay, thanks, everyone.  If it's not good at F/8, it can't be any good at F/6.  Cost was less my concern than weight and performance.  Sad that the Pan 35 was introduced 27 years ago and no one has figured out (including Tele Vue, so far) how to engineer this design at a pound or under.  Hard for me to believe eyepiece development is that slow, that we homo sapiens peaked in 1992 for optical design.  Imagine writing such a thing about computers!


Edited by CollinofAlabama, 19 November 2019 - 11:53 AM.


#10 F.Meiresonne

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Posted 19 November 2019 - 01:22 PM

Optics follow  laws op physics...i guess it is not easy to bypass them...

 

Computers?

Sure they have advanced, many possiblities, but  they don't work very stable..issues all the time. If you don't have a certain expertise you run into issues all the time you can't solve....

 

The MS-DOS computer many years ago was far less advanced ,but quite stable and easier for novices to work with...

 

Progressgrin.gif


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#11 nicoledoula

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Posted 19 November 2019 - 02:37 PM

Baader Aspheric 31mm is not a viable option at F/6 either for the same reasons. Not nearly enough "better".


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#12 havasman

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Posted 19 November 2019 - 02:58 PM

Taking that fast scope's steeper light cone delivered to the focal plane, magnifying it and delivering it to the exit pupil while maintaining as coherent a wavefront as possible seems to take glass, more of it and more exotic, and a precise housing and those things bring weight. So better corrected eyepieces are often (usually?) heavier.

 

I've yet to see a scope mount that could not be made to accommodate a suitable range of eyepiece weights fairly conveniently, some more conveniently than others. That capability has increased over time for different scope types roughly in parallel with the development of heavier, better corrected eyepieces.


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#13 John Huntley

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Posted 19 November 2019 - 06:38 PM

Baader Aspheric 31mm is not a viable option at F/6 either for the same reasons. Not nearly enough "better".

Not even at F/7.5 really, I found. OK in an F/10 SCT though.


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#14 CollinofAlabama

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Posted 19 November 2019 - 07:17 PM

Optics follow  laws op physics...i guess it is not easy to bypass them...

 

Computers?

Sure they have advanced, many possiblities, but  they don't work very stable..issues all the time. If you don't have a certain expertise you run into issues all the time you can't solve....

Puleez!  Meiresonne, NOBODY would use a PC from 1992 for anything other than an old game they loved back then.  Otherwise, for productivity, it is JUNK!  Even a 5th generation i5 would crush it at any spreadsheet, word processing, and especially graphics task, and that same 5th generation i5 is pretty lame compared to a 9th Generation i7 system -- these last two PCs are four years apart in time, not 27.

 

But to be more specific, the heaviest DeLite weighs less than the lightest Radian.  And the Radians were introduced 6 years after the Pan 35.  Folks, it's way past time for TeleVue to address this, but even if they don't someone else should.  It's truly sad that Explore Scientific has only cloned the Panoptics, hardly addressing the weight issue at all.  I agree about the Baader Aspheric 31mm, btw, as I had that one and sold it long ago given its dismal performance in an F/7 refractor I had at the time.  And Baader's lame effort to address weight, at the cost of good edge control, begs the question.  And don't give me "laws of physics".  If the laws of physics hadn't been optimized by Dellechiaie the DeLites couldn't weigh any less than the Radians -- but they do.  In other words, TeleVue has bothered to replace the heavy Radians with an even larger AFOV offering that all weigh less -- in some cases a lot less -- than the Radians.  And they did this in less time than the Panoptics are staring at the beginning of the 3rd decade of the 21st century.

 

TeleVue should be ashamed of themselves for selling the Pan 35 -- on sale -- for $351!  I don't blame them for not wanting to pursue the bottom of the market, and the DeLites are not priced to compete with Celestron X-Cels, but the DeLites are more affordable and do genuinely represent innovation relative to the Radians they replaced in many ways, including weight.

 

It's WAY past time for optical designers to get off their complacent, 1990's designs, or clones thereof.  The 3rd decade of the 21st century is calling.  Anybody home?  TeleVue?  Baader?  Explore Scientific?  Anyone else?


Edited by CollinofAlabama, 19 November 2019 - 07:33 PM.


#15 russell23

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Posted 19 November 2019 - 08:41 PM

Okay, thanks, everyone.  If it's not good at F/8, it can't be any good at F/6.  Cost was less my concern than weight and performance.  Sad that the Pan 35 was introduced 27 years ago and no one has figured out (including Tele Vue, so far) how to engineer this design at a pound or under.  Hard for me to believe eyepiece development is that slow, that we homo sapiens peaked in 1992 for optical design.  Imagine writing such a thing about computers!

I think the closest thing to what you are looking for is the 30mm APM UFF.   It is excellent - sharp to the edge -  in my 102mm f/7 APO's.   At $229 it is a steal IMO.   But I would want to know what others say about it at f/6 or f/5.   In my 61mm f/5.9 APO it was not very good at the edge, but that scope has significant field curvature.  It also started to show some edge falloff (but not horrible) in my 80mm f/7 APO which has more field curvature than the 102mm f/7.

 

So I'm inclined to think that probably as long as the focal length is 600mm or longer, the field curvature of a refractor should not be a problem for the 30mm APM UFF.  I don't know how it will handle f/6 dobs. 


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#16 CollinofAlabama

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Posted 19 November 2019 - 09:36 PM

Dave, I appreciate your conscientious response.  I'm not all that wild about the 30mm APM because it weighs 19.6 ounces, which is heavier than my Explore Scientific 28mm 68°, and only offers a small increase in TFOV relative to this eyepiece.  Yes, it's more, but it's not a lot more, and it is a lot heavier.  If I'm closing in on 20 ounces for an eyepiece, I'm expecting a similarly huge increase in TFOV, not the modest amount the APM offers over the more svelt ES 28mm 68°.  I didn't make that clear earlier, and I'm sorry about that, but the Pan 35 (and, theoretically the SWAN 33 72°) offer a significant increase in field over the ES 28mm 68°.  The SWAN has, on paper, essentially the same TFOV as the Pan 35.  I suppose in somebody's F/13+ Maksutov, it does.  But since my longest F/ratio'ed scope is my 102GT (97mm actual objective and 1016mm focal length, so F/10.4), and everything else I have is F/6, the SWAN would be a true one trick pony.  And I also already own the SuperView 42mm (which has an actual AFOV of 57°), which actually has very, very good edge of field control, just that the exit pupil for me at F/6 is kind of ridiculous.  I still use it in my F/6 scopes when I'm after the absolute maximum TFOV (like Brocchi's Cluster, the Coathanger).  But only a fool would compare the view to what the costly, ginormous Pan 35 would throw up, all of 27 years in the making.

 

I don't argue that the Pan 35 does it best.  I've looked through 'em plenty.  They're fantastic.  But they're like comparing the 4mm Radian to the 4mm DeLite, weight-wise.  One's an unnecessary pig and the other is not.  They both throw up good views, but one's more up-to-date in weight, glass, etc.  I want the replacement for the Pan.  I'm glad the APM folks are trying, but they're not really making headway.  Even the rather pedestrian TeleVue cloning of Explore Scientific's 28mm 68° still represents a better value for my purposes, and I already own that one.  Glad I do, mind you, but would like to go farther (and much farther than the APM 30mm 70°), and still stay under 20 ounces.


Edited by CollinofAlabama, 20 November 2019 - 12:20 AM.


#17 russell23

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Posted 19 November 2019 - 10:15 PM

Keep in mind the 30mm APM has a 38mm field stop so it is the same as the 35mm Pan and about 6oz lighter.  The 28mm ES68 has a 31.8mm field stop.   In my 102mm f/7 the 30mm APM provides a 3.05 deg field while the 28mm ES68 provides a 2.55 deg field. 
 

It might not be as light as you are looking for, but the TFOV gain is more than it might seem.  I’m like you in that I would prefer less than 1 lb eyepieces, but the 30mm APM feels more like the 28mm ES68 than the 35mm Pan.

 

edit: 35mm Pan has a 38.7mm field stop so it would give a 3.11 deg field in my 102mm f/7.


Edited by russell23, 19 November 2019 - 10:17 PM.

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#18 Jon Isaacs

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Posted 20 November 2019 - 03:33 AM

Okay, thanks, everyone.  If it's not good at F/8, it can't be any good at F/6.  Cost was less my concern than weight and performance.  Sad that the Pan 35 was introduced 27 years ago and no one has figured out (including Tele Vue, so far) how to engineer this design at a pound or under.  Hard for me to believe eyepiece development is that slow, that we homo sapiens peaked in 1992 for optical design.  Imagine writing such a thing about computers!

 

I don't argue that the Pan 35 does it best.  I've looked through 'em plenty.  They're fantastic.  But they're like comparing the 4mm Radian to the 4mm DeLite, weight-wise.

 

 

Colin:

 

There's a lot of difference between a 4 mm eyepiece and a 35 mm eyepiece. Making a lightweight 4 mm eyepiece is very different because of the diameter of the lenses required. There are ~35 mm SWAs that are lighter than the 35 mm Panoptic but there are none that are lighter and as well corrected.  

 

The same is true of the 31 mm Nagler, it's a 20 year old design, no one has bested it..

 

It takes glass to produced a well corrected wide field image in a longer focal length eyepiece.. That's a fact of life..

 

Your agenda seems to put weight as a top priority. As long as that's the case, you'll be hoping that lightweight 2 inch eyepieces like the 33mm Swan will somehow offer the performance of the 35 mm Panoptic.. in the end, you'll always be forced to compromise..   

 

Jon



#19 CollinofAlabama

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Posted 21 November 2019 - 05:54 PM

Dave, I called up Don Pensack of EyepiecesEtc.com and he’s got an APM UFF 30mm headed my way.  Thank you SO much for forcing me to re-educate myself about TFoV and field stop, something I’d glanced at, but always lazily used the simplistic TFOV=AFOV/Mag.  Well, after adjusting to the 57.2957795 (180/Pi) business, I determined you were right, and the APM 30mm really did have more TFOV to offer than I’d thought — less than the Pan 35, yes, but not so far behind the ES 34mm 68° that I could see bothering with its greater weight was, indeed, worth it.  Sí, vale la pena, señor.  Long story short, Mr. Pensack is taking care of me (after clearing I’d be using this at F/6 & above, which I will).

 

Muchas gracias, amigo!



#20 nicoledoula

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Posted 21 November 2019 - 07:05 PM

IMO "F/6 and above" really means F/8 or even F/10 and above.  



#21 Miranda2525

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Posted 21 November 2019 - 08:12 PM

https://www.cloudyni...ial-impression/



#22 CollinofAlabama

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Posted 22 November 2019 - 12:46 AM

Nicole, APM doesn’t specify anything about focal ratio.  I agree that, generally, when a vendor says “great at F/6 and above”, you’re lucky if it performs okay at F/8.  But I didn’t hear this from any ole vendor;  it came straight from the mouth of Don Pensack with me on the phone.  Perhaps you’re not familiar with him, but I’ve been on CN since 2004, and Don is very trustworthy.  If he says it’s good at F/6 and above, I’m pretty sure it is, and the post above (#21) appears to verify the veracity of Mr. Pensack’s words.  It’s a LOT to read, but since I just plunked down el dinero, worth my time.  But I’ll get to find out soon enough.  This is the second eyepiece I’ve bought so far this past couple of weeks (and I’m pretty well set, generally, and somewhat jaded), but I like to believe my new 3.5mm T6 and now the APM UFF 30mm will do me fine for a while.  Reckon I could end up selling my ES 28mm 68° if I prefer the APM to it a lot, but that remains to be determined in these next weeks of winter.  Oh what a pleasant determination under the heavens!  May imperiled Andromeda, club-wielding Orion, the Venus conjunctions with Optimus Maximus and his Titan father divine the worthiness of the APM.



#23 nicoledoula

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Posted 22 November 2019 - 04:53 PM

If for some reason you need more ER or less weight  than the ES 30mm or 31mm I suppose the APM is your only choice. Subjectivity and hearsay aside, yes, I know who the vendor Don P. is.



#24 junomike

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Posted 22 November 2019 - 05:23 PM

Dave, I called up Don Pensack of EyepiecesEtc.com and he’s got an APM UFF 30mm headed my way.  Thank you SO much for forcing me to re-educate myself about TFoV and field stop, something I’d glanced at, but always lazily used the simplistic TFOV=AFOV/Mag.  Well, after adjusting to the 57.2957795 (180/Pi) business, I determined you were right, and the APM 30mm really did have more TFOV to offer than I’d thought — less than the Pan 35, yes, but not so far behind the ES 34mm 68° that I could see bothering with its greater weight was, indeed, worth it.  Sí, vale la pena, señor.  Long story short, Mr. Pensack is taking care of me (after clearing I’d be using this at F/6 & above, which I will).

 

Muchas gracias, amigo!

Awaiting your eval......



#25 CollinofAlabama

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Posted 22 November 2019 - 07:13 PM

If for some reason you need more ER or less weight  than the ES 30mm or 31mm I suppose the APM is your only choice. Subjectivity and hearsay aside, yes, I know who the vendor Don P. is.

 

Of course, words written on CN mean nothing compared to a person's experience under the stars.  There's no doubt about that.  And this will also be my experience, without anyone else's predilections, just mine.  But I will address this a little bit.  Although I'm getting older (57), I still don't wear glasses -- not to drive, not to read, not for anything.  Well, I live in sunny west Texas, with more hours of sunshine annually than Honolulu, so I wear sunglasses, but no prescription.  Not sure that'll last a lot longer, but right now, that's the case, and I have never worn them.  I can use a 6mm BCO, no problem.  I'm not a big fan of the TV Plossls in the sub 20mm range, because I find their eye relief a bit difficult, but the volcano topped BCOs are not a problem for me, even the 6mm.  Of course, the Nagler 16mm T5 is even easier to use, for me, so the eye relief of any 2" widefield is going to be more than adequate, regardless how bad it might be for someone with glasses.

 

Consequently, eye relief wasn't a concern of mine.  I have a couple of those Orion felt-covered counterweights, and they work well on my 8" F/6 SkyQuest XTPLUS, but I am not about to put magnets against my refractors, baffles and all too important to possibly bend or otherwise bother my light path because of a counterweight required by some eyepiece that needs a diet.

 

So you can see that weight is a primary concern.  It's not my only concern, however, as a former Baader 31mm Aspheric owner, I insist on a modicum of edge of field clarity.  I'm not bothered by a tiny amount of astigmatism at the very edge of the field, but as Dick Gentry so eloquently wrote "Not the outer edge of the field but the outer third", uh, nope, that's not acceptable, at least not for me.  But the fact that I tried the Aspheric 31mm demonstrates my difficulty with accepting heavier eyepieces.  I have been quite happy with my ES 28mm 68º, but I want a little more.  I very much like the view of friends' Pan 35's in their own 8" F/6 dobs, but am put off by the over-pound-and-a-half size.  And even though that's easy enough to defeat in a dob, again, I'm not going the magnetic counterweight route on my refractors.  Not an option.

 

And I don't like the idea of eyepieces that only work in some of my scopes.  I own the SuperView 42mm eyepiece.  It actually has pretty decent edge correction at F/6, but the problem, besides its ridiculous exit pupil for F/6, is that it's a 57º AFOV eyepiece.  It's not really a wide field.  Bigger than a plossl, but not by much.  It has still provided the widest true field of view for me, and, unlike my ES 38mm 68º, I can still fit all the Coathanger in the SV42, framed rather nicely for a 1200mm FL scope.  Although it mostly fits in the ES 28mm 68º, it just barely does.  There is no framing.  It's a very cramped, unappealing kind of thing in the ES, especially compared to the SV42.

 

But a Pan 35 would be better, for sure.  But then it would require a re-balance for my refractors.  I am married with two small kids in the house.  The time I get under the stars is precious.  I'm not wasting it re-balancing my scope -- period.  It gets balanced at the beginning of the night, and I expect that to last the night.  We'll see how the APM affects this, but that's my idea, and I'm sticking to it.

 

I measured my ES 28mm 68º to be 16.9 ounces.  The APM is 19.6 ounces, so when Dave writes that the APM feels more like the ES 28mm than a Pan 35, I believe him.  Also, with the tfov between them, but a little closer to the Pan than the ES 28mm, and that it was well corrected at F/6, well, that was enough for me.  I write this to give folks an idea about my own personal predilections, so you'll know where I'm coming from.  My experiences, good or bad, may or may not apply to you.


Edited by CollinofAlabama, 22 November 2019 - 07:17 PM.

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