16 replies to this topic

[VAviewer]

Howdy y'all,

Any thoughts on the agena 32mm before I buy? Any common defect or caveat I don't know about that explains the low price? 

Thanks,

[SeattleScott]

The usual, poor edge correction in fast scopes, like, say, 10” F4.8 Dobs for example.

[VAviewer]

The usual, poor edge correction in fast scopes, like, say, 10” F4.8 Dobs for example.

Ah, knew there had to be something. Any recs on another 32mm SWA or similar?

[jrmacl]

Howdy y'all,

Any thoughts on the agena 32mm before I buy? Any common defect or caveat I don't know about that explains the low price? 

Thanks,

this is said to be an excellent ep for the price, 22mm 70* - $140:

 

https://www.amazon.c...243&sr=8-3&th=1

 

and a 4.6mm exit pupil may serve you better than the 6.7mm one you would get with the 32mm SWA

Edited by jrmacl, 28 April 2025 - 09:48 PM.

[Astro-Master]

With you 10" F/4.8 1200mm fl a 32mm 70* AFOV eyepiece would have power of 37.5x and a 1.86* degree TFOV with poor edge correction.

 

The Astro Tech 28mm UWA with a measured 84* AFOV in your scope will have a power of 43x and a 1.95* TFOV with good edge correction for $240, this eyepiece is the best value for a top of the line, low power wide field eyepiece IMHO.  

Edited by Astro-Master, 28 April 2025 - 10:41 PM.

[jrmacl]

With you 10" F/4.8 1200mm fl a 32mm 70* AFOV eyepiece would have power of 37.5x and a 1.86* degree TFOV with poor edge correction.

 

The Astro Tech 28mm UWA with a measured 84* AFOV in your scope will have a power of 43x and a 1.95* TFOV with good edge correction for $240, this eyepiece is the best value for a top of the line, low power wide field eyepiece IMHO.  

the 28mm would give a 5.8mm exit pupil versus 4.8mm in the 22mm 70* I recommended, the 22mm would have an even better corrected but smaller 1.28* TFOV at 55x mag. The 70* ep will have less coma, as would the 30mm UFF (6.3 exit pupil/40x mag/1.75* TFOV) if that was also thrown into the mix. I would have a tough time choosing between those 3 ep's but would probably agree with you and choose the 28mm UWA.

Edited by jrmacl, 28 April 2025 - 11:07 PM.

[SeattleScott]

The 30mm UFF is a little better corrected than the 28 UWA, better eye relief, and often cheaper, although it doesn’t go quite as wide.

[Astro-Master]

The 30mm UFF is a little better corrected than the 28 UWA, better eye relief, and often cheaper, although it doesn’t go quite as wide.

The 30mm UFF has a dimmer image than the 28mmUWA, Jon Isaacs and I both noticed a dimmer view with the 30mm UFF, my guess is coatings are not as good. 

[SeattleScott]

The 30mm UFF has a dimmer image than the 28mmUWA, Jon Isaacs and I both noticed a dimmer view with the 30mm UFF, my guess is coatings are not as good.

It’s quite possible the UFF doesn’t have as good of coating, or maybe it’s the extra glass. It is known that it doesn’t have particularly good transmission, especially in Red. That being said, it is also a longer focal length, so when used in a fast Dob, it can produce an oversized exit pupil, possibly reducing the effective aperture of the scope. Given the usual small differences, like a maybe 5% transmission less in Red, it seems if one noticed a somewhat obvious difference in brightness, it probably had to do with this more than actual transmission of the eyepiece. Granted, the OP has a F4.8, so that could be a concern for them as well, although we don’t know how old their eyes are (or how wide they can dilate).

Personally, at F4.8, I use a 24mm. I agree 28mm makes a little more sense than 30 at F4.8 for exit pupil reasons alone. I’m not saying the 30 would be preferred for the OP. Just another option to consider.

Edited by SeattleScott, 29 April 2025 - 07:36 AM.

[Astro-Master]

It’s quite possible the UFF doesn’t have as good of coating, or maybe it’s the extra glass. It is known that it doesn’t have particularly good transmission, especially in Red. That being said, it is also a longer focal length, so when used in a fast Dob, it can produce an oversized exit pupil, possibly reducing the effective aperture of the scope. Given the usual small differences, like a maybe 5% transmission less in Red, it seems if one noticed a somewhat obvious difference in brightness, it probably had to do with this more than actual transmission of the eyepiece. Granted, the OP has a F4.8, so that could be a concern for them as well, although we don’t know how old their eyes are (or how wide they can dilate).

Personally, at F4.8, I use a 24mm. I agree 28mm makes a little more sense than 30 at F4.8 for exit pupil reasons alone. I’m not saying the 30 would be preferred for the OP. Just another option to consider.

The night I compared the 30mm UFF and the 28mm UWA, I also compared it with my Baader 31mm using my 18" F/4.5 without a Paracorr.

 

The Baader 31 had the brightest image with an exit pupil of 6.88mm and only 6 elements and some of the best coatings I ever used, but the edge correction was not very good.

 

The 30mm UFF with an exit pupil of 6.66mm had a bit better edge correction than the 28mm UWA, but the edge looked very good in the 28mm, and the image was noticeably brighter even with a smaller 6.22mm exit pupil.  

 

I ended up ordering the Astro Tech 28mm UWA the next day for $200, and I still don't think you can beat it for twice the price!

Edited by Astro-Master, 29 April 2025 - 01:51 PM.

[Jon Isaacs]

My two cents:

 

The 30 mm UFF and the 28 mm UWA are both very good eyepieces. The 30 mm has more eye relief and is sharper at the edge, the 28 mm offers a widerfield, a little more magnification and maybe under some circumstances a a somewhat brighter image. 

 

The place I've noticed the difference is in low contrast nebulae like the Cats Or Paw with an O-lll filter. 

 

Coma is a complicated issue but in my mind, I don't give any advantage to a 70° eyepiece over an 82° because it shows less coma. It shows less coma for the same reason it shows fewer stars, the field is narrower. 

 

The ultimate eyepiece in this is category is the 31 mm Nagler. It's sharp-sharp across the field, has good eye relief and high transmission. It also weighs about 1000 grams and costs $700.

 

I have one but use the 28 mm UWA (680:grams) and the 30 mm UFF (550 grams) because they are still quite good but are more manageable 

 

 

I have also had two of the 32 mm SWAs. I've used them in my 16 inch F/4.4 without a coma corrector.

 

There is no doubt that they show significant off-axis astigmatism, stars a blurred in the outer field. But that doesn't mm make them unusable, they're not so pretty as the others but as a finder eyepiece, they're still effective and with a cup half-full attitude, the views are quite pleasing.

 

If you have $100 to spend the 32 mm SWA is workable. 40 years ago, coma correctors and well corrected eyepieces like these others did not exist. Eyepieces like the 32 mm SWA was what there was. It will provide a 1.91° field in a scope with a 1200 mm focal length, the 31 mm Nagler provides a 2.01° field, the 28mm UWA,ba 1.95° field and the 30 mm UFF a 1 77° field.

 

The 32 mm SWA has plenty of eye relief and weighs about 350 grams so it is less likely to mess with your Dob's balance.

 

The distinction I make is that the 30 mm UFF and 28 mm UWA are "keepers". They're very good eyepieces and you are not thinking, "someday I'll get a better eyepiece "

 

The 32 mm SWA is effective and can be enjoyable but the owner of an F/5 Dob will probably want to upgrade to something better sometime down the road.  The two most likely candidates:

 

The 28 mm UWA or the 30 mm UFF 

 

Note that I did not include the 22 mm 70° eyepiece. That's another discussion. You can achieve a 1.3° field with 1.25 inch eyepieces.. 

 

Jon

[jrmacl]

My two cents:

 

The 30 mm UFF and the 28 mm UWA are both very good eyepieces. The 30 mm has more eye relief and is sharper at the edge, the 28 mm offers a widerfield, a little more magnification and maybe under some circumstances a a somewhat brighter image. 

 

The place I've noticed the difference is in low contrast nebulae like the Cats Or Paw with an O-lll filter. 

 

Coma is a complicated issue but in my mind, I don't give any advantage to a 70° eyepiece over an 82° because it shows less coma. It shows less coma for the same reason it shows fewer stars, the field is narrower. 

 

The ultimate eyepiece in this is category is the 31 mm Nagler. It's sharp-sharp across the field, has good eye relief and high transmission. It also weighs about 1000 grams and costs $700.

 

I have one but use the 28 mm UWA (680:grams) and the 30 mm UFF (550 grams) because they are still quite good but are more manageable 

 

 

 

I have also had two of the 32 mm SWAs. I've used them in my 16 inch F/4.4 without a coma corrector.

 

There is no doubt that they show significant off-axis astigmatism, stars a blurred in the outer field. But that doesn't mm make them unusable, they're not so pretty as the others but as a finder eyepiece, they're still effective and with a cup half-full attitude, the views are quite pleasing.

 

If you have $100 to spend the 32 mm SWA is workable. 40 years ago, coma correctors and well corrected eyepieces like these others did not exist. Eyepieces like the 32 mm SWA was what there was. It will provide a 1.91° field in a scope with a 1200 mm focal length, the 31 mm Nagler provides a 2.01° field, the 28mm UWA,ba 1.95° field and the 30 mm UFF a 1 77° field.

 

The 32 mm SWA has plenty of eye relief and weighs about 350 grams so it is less likely to mess with your Dob's balance.

 

The distinction I make is that the 30 mm UFF and 28 mm UWA are "keepers". They're very good eyepieces and you are not thinking, "someday I'll get a better eyepiece "

 

The 32 mm SWA is effective and can be enjoyable but the owner of an F/5 Dob will probably want to upgrade to something better sometime down the road.  The two most likely candidates:

 

The 28 mm UWA or the 30 mm UFF 

 

Note that I did not include the 22 mm 70° eyepiece. That's another discussion. You can achieve a 1.3° field with 1.25 inch eyepieces.. 

 

Jon

This is so why I'm glad we have CN, Jon has every ep being discussed and tells it to you straight. I just don't think anyone could hope for a better answer to the question than this and without CN we'd be in the dark - pun intended.

[jrmacl]

My two cents:

 

The 30 mm UFF and the 28 mm UWA are both very good eyepieces. The 30 mm has more eye relief and is sharper at the edge, the 28 mm offers a widerfield, a little more magnification and maybe under some circumstances a a somewhat brighter image. 

 

The place I've noticed the difference is in low contrast nebulae like the Cats Or Paw with an O-lll filter. 

 

Coma is a complicated issue but in my mind, I don't give any advantage to a 70° eyepiece over an 82° because it shows less coma. It shows less coma for the same reason it shows fewer stars, the field is narrower. 

 

The ultimate eyepiece in this is category is the 31 mm Nagler. It's sharp-sharp across the field, has good eye relief and high transmission. It also weighs about 1000 grams and costs $700.

 

I have one but use the 28 mm UWA (680:grams) and the 30 mm UFF (550 grams) because they are still quite good but are more manageable 

 

 

 

I have also had two of the 32 mm SWAs. I've used them in my 16 inch F/4.4 without a coma corrector.

 

There is no doubt that they show significant off-axis astigmatism, stars a blurred in the outer field. But that doesn't mm make them unusable, they're not so pretty as the others but as a finder eyepiece, they're still effective and with a cup half-full attitude, the views are quite pleasing.

 

If you have $100 to spend the 32 mm SWA is workable. 40 years ago, coma correctors and well corrected eyepieces like these others did not exist. Eyepieces like the 32 mm SWA was what there was. It will provide a 1.91° field in a scope with a 1200 mm focal length, the 31 mm Nagler provides a 2.01° field, the 28mm UWA,ba 1.95° field and the 30 mm UFF a 1 77° field.

 

The 32 mm SWA has plenty of eye relief and weighs about 350 grams so it is less likely to mess with your Dob's balance.

 

The distinction I make is that the 30 mm UFF and 28 mm UWA are "keepers". They're very good eyepieces and you are not thinking, "someday I'll get a better eyepiece "

 

The 32 mm SWA is effective and can be enjoyable but the owner of an F/5 Dob will probably want to upgrade to something better sometime down the road.  The two most likely candidates:

 

The 28 mm UWA or the 30 mm UFF 

 

Note that I did not include the 22 mm 70° eyepiece. That's another discussion. You can achieve a 1.3° field with 1.25 inch eyepieces.. 

 

Jon

If you were in VAviewer shoes, who has the 7mm X-Cel (185x) and a 17mm SWA (70x), would you think then the 32mm SWA is a good idea and the money saved could go to another ep, the 5mm X-Cel for 240x or a paradigm or something wider from AT? Even a $15 Barlow would get 141x and 105x with the 17mm SWA, and 370x and 277x with the 7mm X-Cel

Edited by jrmacl, 30 April 2025 - 05:32 AM.

[Jon Isaacs]

If you were in VAviewer shoes, who has the 7mm X-Cel (185x) and a 17mm SWA (70x), would you think then the 32mm SWA is a good idea and the money saved could go to another ep, the 5mm X-Cel for 240x or a paradigm or something wider from AT? Even a $15 Barlow would get 141x and 105x with the 17mm SWA, and 370x and 277x with the 7mm X-Cel

 

I think a low power, wide field eyepiece that serves as a finder eyepiece is always helpful for someone with a 10 inch Dob, particularly someone just beginning.

 

Jon

[scotsman328i]

I bought this 32mm Agena SWA ocular to use with my Baader Mk.IV zoom to show a wider field at lower power at outreach events. Used it twice so far. It’s actually quite good, though it does coma out on the last 15% or so of the FOV, but overall it’s perfect for the price point, and having sticky little fingers from Pepsi and Cheetos all over it. lol.

[MrsM75]

Following this thread to see the reviews, I am thinking of buy one too, but the 1.25 inch one. It seem like a good price for a 82 deg fov

[jrmacl]

Following this thread to see the reviews, I am thinking of buy one too, but the 1.25 inch one. It seem like a good price for a 82 deg fov

if you are taking about the SWA eyepieces, they are 70 degrees, not 82 degrees