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2" low mag eyepiece for XT8

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#1 Enceladust

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Posted 01 December 2020 - 04:33 PM

Hello all, this is my first post.

 

I am new to this. I have acquired an orion XT8 with two 1.25" EPs (10mm, 25mm). The first thing I would like to invest in would be a decent 2" eyepiece. I have been doing some reading and it appears that a Q70 / Agena SWA 32 mm would seem like a good choice. The price also seems reasonable; I am not quite ready for multi-hundred dollars EPs yet. Would you agree with this pick? What else would you recommend in that focal length vicinity and price range (I am flexible).

 

Also, if you think you have something for sale you think I might be interested in, obviously I am interested to hear about it since I cannot post in the classified section for 30 days!

 

Thank you!!


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#2 SeattleScott

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Posted 01 December 2020 - 04:49 PM

You won’t beat it for the price. There will be distortion near the edge of the field but you have to pay over twice as much to correct that.

It should be a good fit from an exit pupil perspective and maximizing the field of view without vignetting becoming an issue.

Scott
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#3 Bean614

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Posted 01 December 2020 - 04:54 PM

Those are basically identical, and very good choices for that scope!  Your Dob is an f/6, so it's more forgiving of less expensive eyepieces than faster scopes. You'll hardly notice the small bit of distortion near the edge.


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#4 SeattleScott

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Posted 01 December 2020 - 05:48 PM

The advantage of not being used to $250 eyepieces is you tend to be more tolerant of the faults of $100 eyepieces.
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#5 spaceoddity

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Posted 01 December 2020 - 06:02 PM

Yeah that would be about the best you will find in the sub $100 price range. The 38mm of the same lines would also work in your scope(6.3 exit pupil), perform about the same, and give a little bit wider field. 


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#6 Thomas_M44

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Posted 01 December 2020 - 08:22 PM

Hello all, this is my first post.

 

I am new to this. I have acquired an orion XT8 with two 1.25" EPs (10mm, 25mm). The first thing I would like to invest in would be a decent 2" eyepiece. I have been doing some reading and it appears that a Q70 / Agena SWA 32 mm would seem like a good choice. The price also seems reasonable; I am not quite ready for multi-hundred dollars EPs yet. Would you agree with this pick? What else would you recommend in that focal length vicinity and price range (I am flexible).

 

Also, if you think you have something for sale you think I might be interested in, obviously I am interested to hear about it since I cannot post in the classified section for 30 days!

 

Thank you!!

The 32mm focal length is as long as you would want to go, because with longer focal-length eyepieces (such as the 38mm and 40mm available on the market) will cause the secondary mirror shadow of your telescope to appear visible --and you'll want to avoid this.

 

Also: I would suggest avoiding the Agena SWA or SWAN eyepieces you are looking at, or similar 5-element 70-degree eyepieces because I know for a fact that a considerable portion the outer field will be *strongly* astigmatic/distorted in an f/6 telescope.

 

With all due respect to other's expressed opinions, I personally own the related 5-element SWAN 40mm, and even in my f/7 refractor the outer field has a lot of aberration. 

 

These Agena and William Optics SWA/SWAN and similar 5-element type 70-degreeish eyepieces are derivative of the classic Erfle design, and really only produce clean outer fields in telescopes of f/10 and slower.

 

For $230 or less you can get the 30mm APM Ultra Flat Field which produces 70-degrees AFOV and will be extremely clean across the field of view even in your f/6 scope. this is one of the very best eyepieces on the market today in that AFOV range.  Clones of this APM 30mm are offered by other manufacturers for less than $200, and they should be good also.

 

Below linked is a very affordable alternative made in USA 32mm 2-inch 60-degree AFOV Plossl type eyepiece which should produce a *much* better-corrected field in your f/6 scope that the Erfle-derived SWA series you are contemplating.

 

FYI: Don't let the unorthodox nature or low price of Gary Russell's eyepieces scare you. Gary Russell has been building unique eyepieces for a few decades now, and is well known in the astronomical community. He obtains high-quality surplus lens sets, and machines his own Delrin eyepiece bodies/barrels.

 

https://www.ebay.com...oIAAOSwPzhaKF-s

 

But seriously, again, the SWA you mention, and similar Erfle-derived 5-element eyepieces will aberrate  pretty badly in the outer field at f/6. wink.gif

 

Have fun!


Edited by Thomas_M44, 01 December 2020 - 08:30 PM.

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#7 BillP

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Posted 01 December 2020 - 08:45 PM

If indeed that eyepiece produces a 60 deg AFOV then it would give the OP more than half a degree more of TFOV than their stock 25mm Plossl (1 deg vs 1.6 deg in the 8" f/5.9).


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#8 LDW47

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Posted 01 December 2020 - 09:08 PM

I enjoyed the WO SWAN 40mm, 72° ep in my 2 8” dobs, the Double Cluster was amazing at about 30x and 2.4° TFOV and then for a great change I would add in a GSO 2x barlow !



#9 LDW47

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Posted 01 December 2020 - 09:10 PM

The 32mm focal length is as long as you would want to go, because with longer focal-length eyepieces (such as the 38mm and 40mm available on the market) will cause the secondary mirror shadow of your telescope to appear visible --and you'll want to avoid this.

 

Also: I would suggest avoiding the Agena SWA or SWAN eyepieces you are looking at, or similar 5-element 70-degree eyepieces because I know for a fact that a considerable portion the outer field will be *strongly* astigmatic/distorted in an f/6 telescope.

 

With all due respect to other's expressed opinions, I personally own the related 5-element SWAN 40mm, and even in my f/7 refractor the outer field has a lot of aberration. 

 

These Agena and William Optics SWA/SWAN and similar 5-element type 70-degreeish eyepieces are derivative of the classic Erfle design, and really only produce clean outer fields in telescopes of f/10 and slower.

 

For $230 or less you can get the 30mm APM Ultra Flat Field which produces 70-degrees AFOV and will be extremely clean across the field of view even in your f/6 scope. this is one of the very best eyepieces on the market today in that AFOV range.  Clones of this APM 30mm are offered by other manufacturers for less than $200, and they should be good also.

 

Below linked is a very affordable alternative made in USA 32mm 2-inch 60-degree AFOV Plossl type eyepiece which should produce a *much* better-corrected field in your f/6 scope that the Erfle-derived SWA series you are contemplating.

 

FYI: Don't let the unorthodox nature or low price of Gary Russell's eyepieces scare you. Gary Russell has been building unique eyepieces for a few decades now, and is well known in the astronomical community. He obtains high-quality surplus lens sets, and machines his own Delrin eyepiece bodies/barrels.

 

https://www.ebay.com...oIAAOSwPzhaKF-s

 

But seriously, again, the SWA you mention, and similar Erfle-derived 5-element eyepieces will aberrate  pretty badly in the outer field at f/6. wink.gif

 

Have fun!

As a matter of fact the views were still pretty awesome !



#10 SpaceConqueror3

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Posted 01 December 2020 - 09:17 PM

I have a 2" 18mm SWA from Russell Optics which I've been happy to use with my XT10 dob. They have a 2" 32mm Plossl which could perhaps be a good bargain for you to consider. 

 

https://www.ebay.com...oIAAOSwPzhaKF-s



#11 CeleNoptic

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Posted 01 December 2020 - 09:32 PM

Hello all, this is my first post.
 
I am new to this. I have acquired an orion XT8 with two 1.25" EPs (10mm, 25mm). The first thing I would like to invest in would be a decent 2" eyepiece. I have been doing some reading and it appears that a Q70 / Agena SWA 32 mm would seem like a good choice. The price also seems reasonable; I am not quite ready for multi-hundred dollars EPs yet. Would you agree with this pick? What else would you recommend in that focal length vicinity and price range (I am flexible).
 
Also, if you think you have something for sale you think I might be interested in, obviously I am interested to hear about it since I cannot post in the classified section for 30 days!
 
Thank you!!

 

Welcome to CN flowerred.gif .

 

If you look at my signature you'll see pretty much similar F/6 Dob and the 32mm Agena SWA. My workhose budget wide field/finder eyepiece. It's not perfect, but if you don't want to pay $210 for Meade Series 5000 2" Ultra High-Definition Eyepiece - 30mm which is a slightly cheaper rebrand of highly praised APM UFF, than as others have said you won't find anything better under $100. It's a good budget eyepiece whatever anybody says. Of course, it's solely my personal opinion. The Agena SWA has 70*AFOV and will give you ~1.9*TFOV.

 

In perspective, I also would recommend you to look into 15-17mm UWA eyepieces for faint DSOs and 10-12mm wide field for brighter DSOs plus any good Barlow, e.g. 2x ES Focal Extender.
 


Edited by CeleNoptic, 01 December 2020 - 09:35 PM.

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#12 Thomas_M44

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Posted 02 December 2020 - 02:05 AM

As a matter of fact the views were still pretty awesome !

I have that "40mm" WO SWAN also.

 

BTW: It's actually a 38mm and 70-degree eyepiece. The WO marketing department evidently put a little "magic juice" on the specs smirk.gif  

 

But hey, what's a little 2mm and 2-degrees between friends? lol.gif

 

I do agree it's a pretty nice 38mm Erfle.

 

Personally, I  enjoy the eyepiece too, even with the very substantial outer-field astigmatism at f/7.

 

I imagine, however, it might be quite a disappointment of expectations for many purchasers when they discover the somewhat limited well-corrected field possible their modest focal-ratio telescopes.


Edited by Thomas_M44, 02 December 2020 - 01:18 PM.


#13 Thomas_M44

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Posted 02 December 2020 - 02:08 AM

If indeed that eyepiece produces a 60 deg AFOV then it would give the OP more than half a degree more of TFOV than their stock 25mm Plossl (1 deg vs 1.6 deg in the 8" f/5.9).

Time for the flashlight test, I suppose smile.gif



#14 Enceladust

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Posted 02 December 2020 - 02:22 AM

Hi again guys,

 

I really enjoyed reading your responses so far and Thomas you got me curious about the Gary Russell eyepiece which I never heard about before. Keep the discussion going hopefully, incredibly interesting to hear the opinions and suggestions of you all!

 Thanks!!



#15 Adam Long

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Posted 02 December 2020 - 03:45 AM

Have a look at the Aero ED eyepieces. 6-element, wide angle view, surprisingly light. 30, 35 or 40mm, I have the 35mm which gives the largest true field of any eye piece I own - noticeably wider than my ES 34/68 which is more than twice the weight. Sharp and contrasty on axis, less so at the edges (@f/4.7). A bonus is the afov is larger than the stated 68 degrees, at least 70, matching the APM 30mm. Under £100 in the U.K. so at the bottom end of 2" prices.


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#16 BDS316

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Posted 02 December 2020 - 08:37 AM

This is an interesting thread.  I've owned an XT8 for a long time, and as president of a medium sized astronomy club I've had the opportunity to use a large number of low power, 2 inch eyepieces with it.

 

If you want an eyepiece that will show you more sky than you could see with a 1.25 inch, 32mm plossl, without significant edge-of-field abberations at f/6, you basically have two choices:

 

1.  Spend the money to get a premium or at least semi-premium eyepiece, like a Panoptic, Nagler, ES 68 or 82, or the  30mm APM UFF

 

2.  Limit the apparent field of view to 60 degrees or so.  This is what the 2 inch 32mm Plossl discussed above does.  Or pick up a 2 inch 30mm Sterling Plossl on the used market. I think the 40mm Sterling Plossl gives too large an exit pupil with the XT8 and faster scopes.  Also possibly available used would be the 2" Orion Optiluxe 32mm with a 58 degree apparent field of view, and UO used to sell a 2" 32mm Konig with a 60 degree AFOV.

 

IMO, YMMV.


Edited by BDS316, 02 December 2020 - 09:30 AM.

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#17 BillP

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Posted 02 December 2020 - 08:41 AM

THEY JUST CAME UP IN THE CLASSIFIEDS!!!

 

https://www.cloudyni...-starter-2-eps/


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#18 LDW47

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Posted 02 December 2020 - 09:00 AM

I have that "40mm" WO SWAN also.

 

BTW: It's actually a 38mm and 70-degree eyepiece. The WO marketing department evidently put a little "magic juice" on the specs smirk.gif  

 

But hey, what's a little 2mm and 2-degrees between friends? lol.gif

 

I do agree it's a pretty nice 38mm Erfle.

 

Personally, I  enjoy the eyepiece too, even with the very substantial outer-field astigmatism at f/7.

 

I imagine, however, it might be quite a disappointment of expectations for many purchasers when they discover the limited well-corrected field in possible their modest focal-ratio telescopes.

I also love my WO 40mm, 72° !  The outer reaches of the FOV are probably not even noticed by many if you only knew the truth, those few degrees are only for the perfectionists to pick at not the real, true viewers on a black, clear nite, the whole field looks great !



#19 LDW47

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Posted 02 December 2020 - 09:03 AM

Hi again guys,

 

I really enjoyed reading your responses so far and Thomas you got me curious about the Gary Russell eyepiece which I never heard about before. Keep the discussion going hopefully, incredibly interesting to hear the opinions and suggestions of you all!

 Thanks!!

I have 6 Russell eps, the views are excellent, they are hand made, and very lite for their size what with the use of Delrin in the body construction and they all sell for less than $100. Google Gary Russells web site !


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#20 BDS316

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Posted 02 December 2020 - 11:36 AM

The 32mm focal length is as long as you would want to go, because with longer focal-length eyepieces (such as the 38mm and 40mm available on the market) will cause the secondary mirror shadow of your telescope to appear visible --and you'll want to avoid this.

 

Also: I would suggest avoiding the Agena SWA or SWAN eyepieces you are looking at, or similar 5-element 70-degree eyepieces because I know for a fact that a considerable portion the outer field will be *strongly* astigmatic/distorted in an f/6 telescope.

 

With all due respect to other's expressed opinions, I personally own the related 5-element SWAN 40mm, and even in my f/7 refractor the outer field has a lot of aberration. 

 

These Agena and William Optics SWA/SWAN and similar 5-element type 70-degreeish eyepieces are derivative of the classic Erfle design, and really only produce clean outer fields in telescopes of f/10 and slower.

 

For $230 or less you can get the 30mm APM Ultra Flat Field which produces 70-degrees AFOV and will be extremely clean across the field of view even in your f/6 scope. this is one of the very best eyepieces on the market today in that AFOV range.  Clones of this APM 30mm are offered by other manufacturers for less than $200, and they should be good also.

 

Below linked is a very affordable alternative made in USA 32mm 2-inch 60-degree AFOV Plossl type eyepiece which should produce a *much* better-corrected field in your f/6 scope that the Erfle-derived SWA series you are contemplating.

 

FYI: Don't let the unorthodox nature or low price of Gary Russell's eyepieces scare you. Gary Russell has been building unique eyepieces for a few decades now, and is well known in the astronomical community. He obtains high-quality surplus lens sets, and machines his own Delrin eyepiece bodies/barrels.

 

https://www.ebay.com...oIAAOSwPzhaKF-s

 

But seriously, again, the SWA you mention, and similar Erfle-derived 5-element eyepieces will aberrate  pretty badly in the outer field at f/6. wink.gif

 

Have fun!

I just visited the Russell website and the 32mm 2 inch Plossl  was nowhere to be found.  Is it ebay only?



#21 droid

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Posted 02 December 2020 - 12:14 PM

contact Gary, hes extremely helpful, and may be able to make it.



#22 Starman1

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Posted 02 December 2020 - 01:05 PM

Look at post #17 and act fast!



#23 Thomas_M44

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Posted 02 December 2020 - 01:23 PM

THEY JUST CAME UP IN THE CLASSIFIEDS!!!

 

https://www.cloudyni...-starter-2-eps/

*Perhaps* the seller is preparing to upgrade to APM UFF's ? lol.gif


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#24 Thomas_M44

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Posted 02 December 2020 - 01:26 PM

I just visited the Russell website and the 32mm 2 inch Plossl  was nowhere to be found.  Is it ebay only?

Yes, go to the Russell Optics Ebay page. That's where he's selling his current offerings:

 

https://www.ebay.com...oIAAOSwPzhaKF-s

 

Gary's home website is awaiting extensive updating.


Edited by Thomas_M44, 02 December 2020 - 01:32 PM.

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#25 spaceoddity

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Posted 02 December 2020 - 04:18 PM

Welcome to CN flowerred.gif .

 

If you look at my signature you'll see pretty much similar F/6 Dob and the 32mm Agena SWA. My workhose budget wide field/finder eyepiece. It's not perfect, but if you don't want to pay $210 for Meade Series 5000 2" Ultra High-Definition Eyepiece - 30mm which is a slightly cheaper rebrand of highly praised APM UFF, than as others have said you won't find anything better under $100. It's a good budget eyepiece whatever anybody says. Of course, it's solely my personal opinion. The Agena SWA has 70*AFOV and will give you ~1.9*TFOV.

 

In perspective, I also would recommend you to look into 15-17mm UWA eyepieces for faint DSOs and 10-12mm wide field for brighter DSOs plus any good Barlow, e.g. 2x ES Focal Extender.
 

I used that same eyepiece in my F/4.7 10" dob for several years and greatly enjoyed using it as a wide field finder/scanner. Sure it's not perfect. The stars at the extreme edge are lines but it definitely gives a nice immersive view. I've since upgraded but if I was on a stricter budget I'd probably still be enjoying it. 

 

On another note, the 38mm will not show the secondary at F/6(6.3 exit pupil which is below the 7 recommendation). A lot of 8" dob owners use that eyepiece. The choice between a 32 or 38 depends on age and how dark your skies are. If you are young and have dark skies, then I'd say the 38 would be best for a wider field. If you are older or view from brighter (city/suburban) skies, then the 32 would be a better choice albeit giving up a little FOV.


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