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2" 32mm Agena SWA vs 30mm GSO plossl and larger eyepiece questions

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#1 ulrichsd

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Posted 06 May 2021 - 08:02 AM

Hi all, some random eyepiece questions and observations...

 

I have the Agena Super Wide Angle 32mm 2" eyepiece, which has a 70 degree field of view ($95).

I just bought a Z10 that came with a 30mm 2" eyepiece, which I'm assuming is this GSO SuperView 2" 68 degree plossl ($65).

 

I compared them last night and the Agena SWA does have a slightly wider field of view (I was viewing the beehive cluster which fits quite nicely at this range), seems a slight bit sharper, and a bit heavier. The Agena also has an annoying lip on the sleeve that makes it difficult to remove easily from the focuser. The Agena seems a little better imo, but not such a difference that I would have purchased it had I already had the GSO plossl.

 

I was wondering if there is any benefit to getting a larger eyepiece for an 10" than 32mm? I know that Agena has a 38mm SWA that is quite a lot heavier. GSO also has a 42mm and a 50mm.

 

Does anyone out there use a >32mm ep for a 10" scope? It is my understanding that anything beyond that is exceeding the exit pupil range for eyesight, so I'm assuming you'd have to scan the eyepiece field if you were to get a larger afov.

 

Thanks!

Scott


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#2 LDW47

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Posted 06 May 2021 - 08:13 AM

Hi all, some random eyepiece questions and observations...

 

I have the Agena Super Wide Angle 32mm 2" eyepiece, which has a 70 degree field of view ($95).

I just bought a Z10 that came with a 30mm 2" eyepiece, which I'm assuming is this GSO SuperView 2" 68 degree plossl ($65).

 

I compared them last night and the Agena SWA does have a slightly wider field of view (I was viewing the beehive cluster which fits quite nicely at this range), seems a slight bit sharper, and a bit heavier. The Agena also has an annoying lip on the sleeve that makes it difficult to remove easily from the focuser. The Agena seems a little better imo, but not such a difference that I would have purchased it had I already had the GSO plossl.

 

I was wondering if there is any benefit to getting a larger eyepiece for an 10" than 32mm? I know that Agena has a 38mm SWA that is quite a lot heavier. GSO also has a 42mm and a 50mm.

 

Does anyone out there use a >32mm ep for a 10" scope? It is my understanding that anything beyond that is exceeding the exit pupil range for eyesight, so I'm assuming you'd have to scan the eyepiece field if you were to get a larger afov.

 

Thanks!

Scott

The 2” WO 40mm SWAN, 72° is a nice performer as well ! Bear in mind it will give you 30x but the exit pupil would be a whopping 8.3mm with a TFOV 2.4°. Your scopes recommended ep range is 19-10mm to maximize it’s performance but like most you can go well outside it. Its your choice ! Good Luck ! PS: But you should have a 2” widefield finder ep like you already have ! PPS: The difference in performance between the two you already have is next to nothing but you are losing about 0.6° TFOV compared to the SWAN !


Edited by LDW47, 06 May 2021 - 08:27 AM.


#3 CrazyPanda

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Posted 06 May 2021 - 08:31 AM

Hi all, some random eyepiece questions and observations...

 

I have the Agena Super Wide Angle 32mm 2" eyepiece, which has a 70 degree field of view ($95).

I just bought a Z10 that came with a 30mm 2" eyepiece, which I'm assuming is this GSO SuperView 2" 68 degree plossl ($65).

 

I compared them last night and the Agena SWA does have a slightly wider field of view (I was viewing the beehive cluster which fits quite nicely at this range), seems a slight bit sharper, and a bit heavier. The Agena also has an annoying lip on the sleeve that makes it difficult to remove easily from the focuser. The Agena seems a little better imo, but not such a difference that I would have purchased it had I already had the GSO plossl.

 

I was wondering if there is any benefit to getting a larger eyepiece for an 10" than 32mm? I know that Agena has a 38mm SWA that is quite a lot heavier. GSO also has a 42mm and a 50mm.

 

Does anyone out there use a >32mm ep for a 10" scope? It is my understanding that anything beyond that is exceeding the exit pupil range for eyesight, so I'm assuming you'd have to scan the eyepiece field if you were to get a larger afov.

 

Thanks!

Scott

Nice mini review of the two.

Assuming your pupils dilate to 7mm, and the Z10 has an F/4.9 focal ratio, you shouldn't really exceed 34.3mm (call it 35mm). That means something like the 35mm Panoptic or 34mm ES68 would be the limits of what you should be put in that scope.

 

If you want a wider true field of view without exceeding the recommended exit pupil limit, you would want to move up into an 82 degree class eyepiece like the 30mm ES82 or 31mm Nagler.

 

The 42mm and 50mm GSO SuperViews basically have the same true field of view as each other because the field of view is governed by field stop size, not focal length. They start getting narrow in apparent field of view as a consequence of trying to put long focal lengths in a 2" barrel. The 42mm and 50mm SuperViews are more appropriate for F/10 SCTs where you need long focal lengths to get bright exit pupils. The F/10 focal ratio of an SCT will work better with the simpler designs of the SuperViews. The 50mm I had was wonderful in my 8" SCT.


Edited by CrazyPanda, 06 May 2021 - 08:32 AM.

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#4 SeattleScott

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Posted 06 May 2021 - 08:48 AM

I use a 24mm 82 AFOV in my 10” F4.8.

Personally I wouldn’t go any higher than 32mm unless I had really dark skies.

Yes the Agena/Swan is considered a minor upgrade over the GSO but not really a cost effective one. Kind of like why spend $90 to get a 10% improvement when you can spend $220 and get a 50% improvement?

Really the way to go wider would be a 30mm 82 AFOV. But a good quality one is very expensive and heavy.

Scott

#5 Jon Isaacs

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Posted 06 May 2021 - 09:10 AM

Scott:

 

I know these eyepieces, I have a 30 mm GSO Superview that's currently loaned out I had the 32 mm 70 degree until I gave it to a friend.  I also have some high end eyepieces for comparison.

 

The GSO Superview is not a Plossl, it's a 5 element design, probably a modified Erfle or something. I agree with your assessment, the 32 mm 70 degree is somewhat better but they're more alike than different.

 

One difference is the Superview does not have a field stop so at the edge of the field is not sharply defined, it's a band of vignetting.  The 42 mm Superview also has no field stop.

 

I also find the 32mm 70 degree is noticeable sharper in the center than the Supervue. Both show significant off-axis astigmatism at F/5.

 

I don't see much of a reason to purchase a longer focal length eyepiece for an F/5 Dob.  The 32 mm 70 degree has a 40 mm field stop, the largest possible is 46 mm so you would go from a 1.83° field to a 2.11° field but you'd be losing magnification and the exit pupil would be approaching 8 mm. The 32mm provides a 6.4 mm exit pupil, plenty large e

 

The 32 mm 70 degree is like a budget version of the 31 mm Nagler, essentially the same focal length and exit pupil and a 1.83° field rather than the Naglers 1.93° field, not a big differednce. Of course it doesn't have that legendary sharpness across the field nor the kilogram weight and high cost.

 

But it fills that same role in a very similar if less perfect way and don't think you'd gain much buying a 38 mm 70 degree or 40 mm 70 degree. Save your money and maybe look to purchasing a better corrected eyepiece sometime in the future.

 

Jon


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#6 ulrichsd

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Posted 06 May 2021 - 11:39 AM

Thanks everyone for the input! Both my celestron 130 and the Z10 are F/5 so eyepieces have the same exit pupil for both, which makes it easy. I do notice that the 32mm in my 130mm Celestron has significantly more wash out / less dark sky compared to my paradigms, which I assume is the 2" eps vs 1.25" picking up more reflected light from the tube (?).

 

The 2” WO 40mm SWAN, 72° is a nice performer as well ! Bear in mind it will give you 30x but the exit pupil would be a whopping 8.3mm with a TFOV 2.4°. Your scopes recommended ep range is 19-10mm to maximize it’s performance but like most you can go well outside it. Its your choice ! Good Luck ! PS: But you should have a 2” widefield finder ep like you already have ! PPS: The difference in performance between the two you already have is next to nothing but you are losing about 0.6° TFOV compared to the SWAN !

Interesting ep and seems like a nice value at $130. It would give a 2.3 tfov (vs the 1.79 for the 32mm swa), but also a 8mm exit pupil - probably best for a slower scope.

 

Nice mini review of the two.

Assuming your pupils dilate to 7mm, and the Z10 has an F/4.9 focal ratio, you shouldn't really exceed 34.3mm (call it 35mm). That means something like the 35mm Panoptic or 34mm ES68 would be the limits of what you should be put in that scope.

 

If you want a wider true field of view without exceeding the recommended exit pupil limit, you would want to move up into an 82 degree class eyepiece like the 30mm ES82 or 31mm Nagler.

 

The 42mm and 50mm GSO SuperViews basically have the same true field of view as each other because the field of view is governed by field stop size, not focal length. They start getting narrow in apparent field of view as a consequence of trying to put long focal lengths in a 2" barrel. The 42mm and 50mm SuperViews are more appropriate for F/10 SCTs where you need long focal lengths to get bright exit pupils. The F/10 focal ratio of an SCT will work better with the simpler designs of the SuperViews. The 50mm I had was wonderful in my 8" SCT.

I compared the tfov for the es8030mm, which would be 1.92 deg vs 1.79 for the SWA 32mm. Which is the same 0.13 deg difference between the Superview 30mm and the SWA 32mm. That makes sense regarding the 40 and 50mm for an SCT vs a dob.

 

I use a 24mm 82 AFOV in my 10” F4.8.

Personally I wouldn’t go any higher than 32mm unless I had really dark skies.

Yes the Agena/Swan is considered a minor upgrade over the GSO but not really a cost effective one. Kind of like why spend $90 to get a 10% improvement when you can spend $220 and get a 50% improvement?

Really the way to go wider would be a 30mm 82 AFOV. But a good quality one is very expensive and heavy.

Scott

Yes, I bought the Agena SWA 32mm a few months ago after reading a positive review and wanting to try a 2" ep in my new Celestron scope, before buying the 10" dob, which came with the 30mm. Just because the Celstron can take a 2" ep doesn't mean it should, so I really just use the 1.25" 25mm as the widest ep for that one.

 

Scott:

 

I know these eyepieces, I have a 30 mm GSO Superview that's currently loaned out I had the 32 mm 70 degree until I gave it to a friend.  I also have some high end eyepieces for comparison.

 

The GSO Superview is not a Plossl, it's a 5 element design, probably a modified Erfle or something. I agree with your assessment, the 32 mm 70 degree is somewhat better but they're more alike than different.

 

One difference is the Superview does not have a field stop so at the edge of the field is not sharply defined, it's a band of vignetting.  The 42 mm Superview also has no field stop.

 

I also find the 32mm 70 degree is noticeable sharper in the center than the Supervue. Both show significant off-axis astigmatism at F/5.

 

I don't see much of a reason to purchase a longer focal length eyepiece for an F/5 Dob.  The 32 mm 70 degree has a 40 mm field stop, the largest possible is 46 mm so you would go from a 1.83° field to a 2.11° field but you'd be losing magnification and the exit pupil would be approaching 8 mm. The 32mm provides a 6.4 mm exit pupil, plenty large e

 

The 32 mm 70 degree is like a budget version of the 31 mm Nagler, essentially the same focal length and exit pupil and a 1.83° field rather than the Naglers 1.93° field, not a big differednce. Of course it doesn't have that legendary sharpness across the field nor the kilogram weight and high cost.

 

But it fills that same role in a very similar if less perfect way and don't think you'd gain much buying a 38 mm 70 degree or 40 mm 70 degree. Save your money and maybe look to purchasing a better corrected eyepiece sometime in the future.

 

Jon

You are correct, the 30mm is not a plossl, the 9mm that also came with the Z10 is a plossl. You are also right, I ran some numbers on these and 32mm is probably the limit as that gives a 6.4mm exit pupil and 1.79 deg tfov. Wow, $670 on the 31mm Nagler :o not sure if that is in my future any time soon, but I do hope to get a chance to look through one some day :)

 

2021-05-06 12_28_27-Microsoft Excel - epmag.xlsx.jpg



#7 LDW47

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Posted 06 May 2021 - 11:54 AM

My 40mm SWAN in my 8” SW dob views of the Double Cluster on an average to above average nite were spectacular as was ......... ! My 2” GSO 2x barlow turned it up a notch.


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#8 SeattleScott

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Posted 06 May 2021 - 12:08 PM

Thanks everyone for the input! Both my celestron 130 and the Z10 are F/5 so eyepieces have the same exit pupil for both, which makes it easy. I do notice that the 32mm in my 130mm Celestron has significantly more wash out / less dark sky compared to my paradigms, which I assume is the 2" eps vs 1.25" picking up more reflected light from the tube (?).

Interesting ep and seems like a nice value at $130. It would give a 2.3 tfov (vs the 1.79 for the 32mm swa), but also a 8mm exit pupil - probably best for a slower scope.

I compared the tfov for the es8030mm, which would be 1.92 deg vs 1.79 for the SWA 32mm. Which is the same 0.13 deg difference between the Superview 30mm and the SWA 32mm. That makes sense regarding the 40 and 50mm for an SCT vs a dob.

Yes, I bought the Agena SWA 32mm a few months ago after reading a positive review and wanting to try a 2" ep in my new Celestron scope, before buying the 10" dob, which came with the 30mm. Just because the Celstron can take a 2" ep doesn't mean it should, so I really just use the 1.25" 25mm as the widest ep for that one.

You are correct, the 30mm is not a plossl, the 9mm that also came with the Z10 is a plossl. You are also right, I ran some numbers on these and 32mm is probably the limit as that gives a 6.4mm exit pupil and 1.79 deg tfov. Wow, $670 on the 31mm Nagler :o not sure if that is in my future any time soon, but I do hope to get a chance to look through one some day :)

2021-05-06 12_28_27-Microsoft Excel - epmag.xlsx.jpg

The obvious one you are missing is the 9-elements 30mm 70 AFOV for $220-240, sold under a few different brands but commonly known as the APM UFF.

Scott
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#9 LDW47

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Posted 06 May 2021 - 12:35 PM

The obvious one you are missing is the 9-elements 30mm 70 AFOV for $220-240, sold under a few different brands but commonly known as the APM UFF.

Scott

Why when the poster already has two very capable eps in that range ? Oh you mean just to have a set of 3  ?


Edited by LDW47, 06 May 2021 - 12:36 PM.


#10 Miranda2525

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Posted 06 May 2021 - 12:37 PM

Why when the poster already has two very capable eps in that range ? Oh you mean just to have a set of 3  ?

They are nowhere capable to the excellent performance of the 30mm APM UFF.


Edited by Miranda2525, 06 May 2021 - 12:38 PM.

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#11 SeattleScott

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Posted 06 May 2021 - 12:40 PM

They are nowhere capable to the excellent performance of the 30mm APM UFF.

Yes this is the point. You can accomplish things with nine elements that you can’t with five.

Scott
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#12 Miranda2525

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Posted 06 May 2021 - 12:41 PM

Yes this is the point. You can accomplish things with nine elements that you can’t with five.

Scott

ubetcha.gif
 



#13 LDW47

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Posted 06 May 2021 - 12:43 PM

Yes this is the point. You can accomplish things with nine elements that you can’t with five.

Scott

I doubt it, if you already have two excellent performers at lower powers, maybe the OP should concentrate on a different size to compliment what they have ? Ya think ?



#14 Jon Isaacs

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Posted 06 May 2021 - 01:05 PM

Why when the poster already has two very capable eps in that range ? Oh you mean just to have a set of 3  ?

 

This is my reasoning based on owing all four eyepieces:

 

- The 30 mm APM offers Nagler like sharpness across the field, more eye relief, weighs 550 grams instead of 1000 grams and costs $250 instead of $650 dollars.  The downside is a 14% narrow field and maybe somewhat lower transmission. It's a good one. 

 

- The 32 mm 70 degree and 30 mm Superview both show a serious amount of off-axis astigmatism at F/5.  Moderately sharp in the center of the field, degrading significantly as one moves away from the center. This is what $100 buys.

 

I purchased the 30 mm APM a few months ago, it's getting more use than the 31 mm Nagler.

 

Some people don't care if the stars towards the edge are far from round and tight, smeared by astigmatism. Some do.

 

If Scott would like sharp, clean stars across the field, the 30 mm UFF is a good, affordable choice. A coma corrector would seal the deal. 

 

Jon


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#15 Miranda2525

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Posted 06 May 2021 - 01:12 PM

This is my reasoning based on owing all four eyepieces:

 

- The 30 mm APM offers Nagler like sharpness across the field, more eye relief, weighs 550 grams instead of 1000 grams and costs $250 instead of $650 dollars.  The downside is a 14% narrow field and maybe somewhat lower transmission. It's a good one. 

 

- The 32 mm 70 degree and 30 mm Superview both show a serious amount of off-axis astigmatism at F/5.  Moderate sharp in the center of the field, degrading significant as one moves away from the center. This is what $100 buys.

 

I purchased the 30 mm APM a few months ago, it's getting more use than the 31 mm Nagler.

 

Some people don't care if the stars towards the edge are far from round and tight, smeared by astigmatism. Some do.

 

If Scott would like sharp, clean stars across the field, the 30 mm UFF is a good, affordable choice. A coma corrector would seal the deal. 

 

Jon

These are words of wisdom from a very experienced observer.


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#16 LDW47

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Posted 06 May 2021 - 01:42 PM

Sometimes, many times the views out towards the edges aren’t as bad as some profess but I won’t say any more about that ! It all depends on how .............. !



#17 ulrichsd

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Posted 06 May 2021 - 01:43 PM

Thanks again to everyone for the feedback!

 

I'm ranged from 32mm down to 4mm (8mm with a barlow). I've only been doing this hobby for 6 months, but have been really happy with the paradigm eyepieces for my 130mm, a big upgrade from the cheapo plastic eps that came with that scope. I just got the Z10 this week and last night was my first night with it, but I'm looking forward to using the 1.25" paradigms more on the bigger scope to see how they hold up.

 

Had I known I'd get a decent 30mm ep with the Z10, I probably wouldn't have ordered the SWA 32mm. But, I'll use what I have for now and eventually upgrade over time. When I do, I will definitely keep the 30mm APM UFF in mind, it sounds like a winner.

 

Thanks!

Scott


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#18 LDW47

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Posted 06 May 2021 - 01:46 PM

Thanks everyone for the input! Both my celestron 130 and the Z10 are F/5 so eyepieces have the same exit pupil for both, which makes it easy. I do notice that the 32mm in my 130mm Celestron has significantly more wash out / less dark sky compared to my paradigms, which I assume is the 2" eps vs 1.25" picking up more reflected light from the tube (?).

 

Interesting ep and seems like a nice value at $130. It would give a 2.3 tfov (vs the 1.79 for the 32mm swa), but also a 8mm exit pupil - probably best for a slower scope.

 

I compared the tfov for the es8030mm, which would be 1.92 deg vs 1.79 for the SWA 32mm. Which is the same 0.13 deg difference between the Superview 30mm and the SWA 32mm. That makes sense regarding the 40 and 50mm for an SCT vs a dob.

 

Yes, I bought the Agena SWA 32mm a few months ago after reading a positive review and wanting to try a 2" ep in my new Celestron scope, before buying the 10" dob, which came with the 30mm. Just because the Celstron can take a 2" ep doesn't mean it should, so I really just use the 1.25" 25mm as the widest ep for that one.

 

You are correct, the 30mm is not a plossl, the 9mm that also came with the Z10 is a plossl. You are also right, I ran some numbers on these and 32mm is probably the limit as that gives a 6.4mm exit pupil and 1.79 deg tfov. Wow, $670 on the 31mm Nagler :o not sure if that is in my future any time soon, but I do hope to get a chance to look through one some day smile.gif

 

attachicon.gif2021-05-06 12_28_27-Microsoft Excel - epmag.xlsx.jpg

You will find that your eps now have over a 6mm exit pupil which is well over the ideal range so ......... .



#19 ulrichsd

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Posted 06 May 2021 - 01:54 PM

You will find that your eps now have over a 6mm exit pupil which is well over the ideal range so ......... .

 

I calculate that the GSO 30mm is 6mm exit pupil and Agena SWA 32mm is 6.4mm exit pupil. I have no idea what my eye's max dilated pupil size is though (I'm 43 and have had Lasik, and now have 20/20 vision, of course that doesn't correlate to better night vision).

 

That does bring up a question though - if you are observing with an eyepiece with an exit pupil larger than your eye's pupil, you only lose the advantage of the extra light / brightness... you'd still have the advantage of a wider field of view (if that is what you were looking for), no? Or is there something I'm missing here?


Edited by ulrichsd, 06 May 2021 - 01:56 PM.


#20 LDW47

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Posted 06 May 2021 - 02:06 PM

I calculate that the GSO 30mm is 6mm exit pupil and Agena SWA 32mm is 6.4mm exit pupil. I have no idea what my eye's max dilated pupil size is though (I'm 43 and have had Lasik, and now have 20/20 vision, of course that doesn't correlate to better night vision).

 

That does bring up a question though - if you are observing with an eyepiece with an exit pupil larger than your eye's pupil, you only lose the advantage of the extra light / brightness... you'd still have the advantage of a wider field of view (if that is what you were looking for), no? Or is there something I'm missing here?

And the views are still wonderful and you will find that most have and use eps, many eps that are higher than the upper ideal limits ! All those theoretical numbers are just numbers, they don’t reflect or tell the story about the great views on either end depending on the sky quality / conditions on a given nite. Thats the interesting part, the fun part, thats what its all about ! And you don’t have to spend several hundred $’s to find that out ! But if you are a picky, theoretical kind of observer then stick with the numbers and associated cost definitely !



#21 SeattleScott

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Posted 06 May 2021 - 02:27 PM

I calculate that the GSO 30mm is 6mm exit pupil and Agena SWA 32mm is 6.4mm exit pupil. I have no idea what my eye's max dilated pupil size is though (I'm 43 and have had Lasik, and now have 20/20 vision, of course that doesn't correlate to better night vision).

That does bring up a question though - if you are observing with an eyepiece with an exit pupil larger than your eye's pupil, you only lose the advantage of the extra light / brightness... you'd still have the advantage of a wider field of view (if that is what you were looking for), no? Or is there something I'm missing here?

Yes you will still have a wider view.

If you get too carried away, there could be a black spot in the middle of the view. This typically is an issue more at 8-10mm exit pupil, but it depends on the viewer and the scope.

There are some downsides, such as the bright, washed out background sky. Especially in light pollution.

Scott
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#22 Jon Isaacs

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Posted 06 May 2021 - 03:41 PM

Sometimes, many times the views out towards the edges aren’t as bad as some profess but I won’t say any more about that ! It all depends on how .............. !

They are what they are. At F/5 stars at the edge are far from round, they're spread out and smeared, I think we both know that. Scott has the 30 mm SV and 32 mm 70 degree, he knows what he sees, I don't have to tell.

There are eyepieces that are free of these aberrations and provide stars at the edge that are essentially as sharp as they are in the center. I wanted Scott to be aware of that. He can decide if and when he upgrades to an eyepiece that provides those sharp to the edge views.

Right now, I think Scott doing the wise thing. He's got a very nice 10 inch Dob, there's a lot of fun, excitement and learning ahead.. I'm envious..

And I think he's well set for eyepieces.  I have quite a number of premium eyepieces that I purcased over past 20 plus years. Very nice.

But I also have what I call my lightweight set, they're good performers with some various issues. And that set seems to be almost exactly the same set as Scott's. Instead of the 32 mm 70 degree, I have the 34 mm 72 degree Svbony which I strongly suspect is the 32 mm 70 degree.

The rest of the set are the 25 mm, 18 mm, 12mm, 8 mm, 5 mm and 3.2 mm Astro-Tech Paradigms, there's a 2x Barlow in there too.. And like Scott, among my scopes is a 10 inch F/5 GSO Dob.

I often spend the evening in the the backyard with the 10 inch Dob with the Lightweight set. It doesn't give up much to the fancy eyepieces, not as wide a field, not as sharp (though the 12mm-8mm-5mm are quite sharp).

But they are wide enough to feel wide and sharp in the center where it matters most, I'm seeing what I want to see, what I know is there to be seen. 

There may come a day wen Scott wants to invest in some "better" eyepieces but I think he's set for now.

Jon


  • CeleNoptic, bdcmd, Bob4BVM and 2 others like this

#23 LDW47

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Posted 06 May 2021 - 04:11 PM

Thanks again to everyone for the feedback!

 

I'm ranged from 32mm down to 4mm (8mm with a barlow). I've only been doing this hobby for 6 months, but have been really happy with the paradigm eyepieces for my 130mm, a big upgrade from the cheapo plastic eps that came with that scope. I just got the Z10 this week and last night was my first night with it, but I'm looking forward to using the 1.25" paradigms more on the bigger scope to see how they hold up.

 

Had I known I'd get a decent 30mm ep with the Z10, I probably wouldn't have ordered the SWA 32mm. But, I'll use what I have for now and eventually upgrade over time. When I do, I will definitely keep the 30mm APM UFF in mind, it sounds like a winner.

 

Thanks!

Scott

When the time comes make sure you look at everything out there, bar none !



#24 LDW47

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Posted 06 May 2021 - 04:25 PM

They are what they are. At F/5 stars at the edge are far from round, they're spread out and smeared, I think we both know that. Scott has the 30 mm SV and 32 mm 70 degree, he knows what he sees, I don't have to tell.

There are eyepieces that are free of these aberrations and provide stars at the edge that are essentially as sharp as they are in the center. I wanted Scott to be aware of that. He can decide if and when he upgrades to an eyepiece that provides those sharp to the edge views.

Right now, I think Scott doing the wise thing. He's got a very nice 10 inch Dob, there's a lot of fun, excitement and learning ahead.. I'm envious..

And I think he's well set for eyepieces.  I have quite a number of premium eyepieces that I purcased over past 20 plus years. Very nice.

But I also have what I call my lightweight set, they're good performers with some various issues. And that set seems to be almost exactly the same set as Scott's. Instead of the 32 mm 70 degree, I have the 34 mm 72 degree Svbony which I strongly suspect is the 32 mm 70 degree.

The rest of the set are the 25 mm, 18 mm, 12mm, 8 mm, 5 mm and 3.2 mm Astro-Tech Paradigms, there's a 2x Barlow in there too.. And like Scott, among my scopes is a 10 inch F/5 GSO Dob.

I often spend the evening in the the backyard with the 10 inch Dob with the Lightweight set. It doesn't give up much to the fancy eyepieces, not as wide a field, not as sharp (though the 12mm-8mm-5mm are quite sharp).

But they are wide enough to feel wide and sharp in the center where it matters most, I'm seeing what I want to see, what I know is there to be seen. 

There may come a day wen Scott wants to invest in some "better" eyepieces but I think he's set for now.

Jon

I agree but some descriptions tend to make the views on the outer points sound absolutely terrible, unbearable, whether this is done intentionally or unintentionally is any ones guess ? Whereas in most cases they aren’t and as many great fellow astronomers, not just I, have said if 75% of the central view is great, is clear and sharp and you don’t want or can’t look past some distortion out where most times there isn’t too much important, then just move your scope so that the edge becomes the centre if there is something out there you really want to see. It only takes a touch of the az, less than a second, that is a lot cheaper than some of these eps that are being mentioned, being pushed ! And as a bonus it frees up a lot of cash to get one or two more accessories one might like incl eyepieces.  PS: And thats the other side of the story !



#25 Thomas_M44

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Posted 06 May 2021 - 04:29 PM

Hi all, some random eyepiece questions and observations...

 

I have the Agena Super Wide Angle 32mm 2" eyepiece, which has a 70 degree field of view ($95).

I just bought a Z10 that came with a 30mm 2" eyepiece, which I'm assuming is this GSO SuperView 2" 68 degree plossl ($65).

 

I compared them last night and the Agena SWA does have a slightly wider field of view (I was viewing the beehive cluster which fits quite nicely at this range), seems a slight bit sharper, and a bit heavier. The Agena also has an annoying lip on the sleeve that makes it difficult to remove easily from the focuser. The Agena seems a little better imo, but not such a difference that I would have purchased it had I already had the GSO plossl.

 

I was wondering if there is any benefit to getting a larger eyepiece for an 10" than 32mm? I know that Agena has a 38mm SWA that is quite a lot heavier. GSO also has a 42mm and a 50mm.

 

Does anyone out there use a >32mm ep for a 10" scope? It is my understanding that anything beyond that is exceeding the exit pupil range for eyesight, so I'm assuming you'd have to scan the eyepiece field if you were to get a larger afov.

 

Thanks!

Scott

F/5 is simply way too fast for *any* Erfle-derived eyepiece (such as the Superview and SWA series) to work well. The off-axis astigmatism is always going to be very considerable.

 

Such erfle-derived eyepieces really don't begin to work particularly well until f/10 or slower.

 

The 30mm APM UFF is a great eyepiece in most ways, however, there is a much cheaper option that is nonetheless high-quality:

 

Russell Optics offers a made-in-USA 2-inch 40mm Plossl with good Taiwan-made lenses for only $50 USD. AFOV is a more modest 50-degrees, but the field should be very sharp in your f/5 scope and view will be brighter due to  the exit-pupil being larger than that of a 30-32mm eyepiece. Eye-relief with this 40mm Plossl is also generous and comfortable:

 

https://www.ebay.com...es/402788950569


Edited by Thomas_M44, 06 May 2021 - 04:31 PM.



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