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1.25inch fixed mag Eyepiece Recommendations?? (1 Viewer)

Ridge Walker

Well-known member
Anyone using spotting scope with 1.25 eyepiece. I'm looking to buy decent fixed mag WA one that give a good image. I posted a thread regarding a cheap Enkeeo 20-60-x80 off the bay for £38 posted. The Zoom is good for the price but has a narrow FOV even on 20x. The eyepiece unscrews from the body, and 1.25inch just slots in perfect. Suggestions appreciated
Cheers all
 

Binastro

Well-known member
The prisms may be undersize so only higher magnification WA eyepieces work properly.

Some astro eyepieces may not reach focus.

The 80mm objective may be vignetted, probably a good thing.

So basically one has to try different astro eyepieces to see which ones work.

B.
 

Ridge Walker

Well-known member
The prisms may be undersize so only higher magnification WA eyepieces work properly.

Some astro eyepieces may not reach focus.

The 80mm objective may be vignetted, probably a good thing.

So basically one has to try different astro eyepieces to see which ones work.

B.

Hi thank for the reply, I have some Plossl eyepieces from a Mak75mm I had. a 16mm 32mm and 40mm. Also a SvBony 20mm x2 Barlow that screw onto the bottom of the eyepiece. I can focus all three with no problem, adding the x2 it wont focus out to 100yds. There's no vignetted. What they all give me which I expected was a slight fish eye effect on the edges. A 19mm give around x25. I was looking at the 19mm Ostara Flat Field WA 60° Eyepiece as an option
 

jring

Well-known member
Hi,

the Ostara Flat Field eyepieces are also known as BST Flat Field series and are unfortunately known for their less than stellar performance in faster scopes. Expect a well pronounced soft edge.

For your spotter (which is probably around f5.5 focal ratio) I would recommend a more complex eyepiece design - maybe one of the 68 deg 6 element series (Explore Scientific 68 deg 16mm or Meade SWA 16mm) or any 82mm series basically - maybe the Skywatcher Nirvana 16mm.

https://www.harrisontelescopes.co.uk/acatalog/ovl16nirvana.html#SID=1677

Please make sure you have a no questions asked return policy as it is quite possible that your spotter will not come to infinity focus with an astro EP.

Joachim
 
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Ridge Walker

Well-known member
Hi,

the Ostara Flat Field eyepieces are also known as BST Flat Field series and are unfortunately known for their less than stellar performance in faster scopes. Expect a well pronounced soft edge.

For your spotter (which is probably around f5.5 focal ratio) I would recommend a more complex eyepiece design - maybe one of the 68 deg 6 element series (Explore Scientific 68 deg 16mm or Meade SWA 16mm) or any 82mm series basically - maybe the Skywatcher Nirvana 16mm.

https://www.harrisontelescopes.co.uk/acatalog/ovl16nirvana.html#SID=1677

Please make sure you have a no questions asked return policy as it is quite possible that your spotter will not come to infinity focus with an astro EP.

Joachim
Thanks for the very informative Info. there's a couple of shops that sell Astro Telescopes about 20mile away. With advice given I will give them a ring. and probably take my scope and test some Eyepieces
Cheers Derek
 

jring

Well-known member
Thanks for the very informative Info. there's a couple of shops that sell Astro Telescopes about 20mile away. With advice given I will give them a ring. and probably take my scope and test some Eyepieces

Hi Derek,

that is indeed the best idea - you see what works right away.

For a decent plain glass scope, a 30x or so wide angle EP usually offers the best view .

Joachim
 

mayoayo

Well-known member
The BST flat field, comes with many brands with the same design,and was, in the 16mm version, the choice of Vortex to be "their" 30x WA, fitted with an adapter for the Swaro bayonet, for the original Razor.And it was very expensive, much more than the 60 euros that costs if you buy the astro version.. I used it on the zen Ray telescope first, and then bought an astro version that used in the Regal 65 and then adapted to the Nikon ED50,, It is a very nice eyepiece and edge performance was good in all those scopes. Henry Link mentioned in one particular post that this eyepiece design could be the eyepiece used in the Nikon SE series.. So can't be that bad.. The only problem I find for field use, is the dust in the field stop shows in the image much more than any other eyepiece I have used, so needs to be handled with care,....
 

jring

Well-known member
Hi,

well, Henry was not too impressed with the performance in this thread...

Joachim

https://www.birdforum.net/showthread.php?t=202943&highlight=bst+flat+field

"Part 3 – The 30XW eyepiece

This is another copy. This time the eyepiece being copied is from the Nikon SE series binoculars. The Zen version does have a slightly wider apparent field, but other than that I could detect no significant difference between the two when I mounted them on the same scope. You might expect this eyepiece design to deliver really good off-axis performance, but in fact it turns out to be more adequate than outstanding when used on a scope. There is some off-axis astigmatism, which oddly reaches a peak around 20 degrees from the center, then gradually diminishes toward the edge. The off-axis performance is OK, but not in the same class with the premium wide field astronomical eyepieces I have on hand for comparison (14mm Pentax XW, 19mm Televue Panoptic) and not quite as good as a 17mm Baader Hyperion. The Zen is quite small and light for a wide field eyepiece with long eye relief. The field is wider and eye relief longer than the zoom at 30x, but off-axis aberrations are worse, so the sweet spot is actually smaller. Too bad Zen didn’t copy the superb Swarovski 30XW, which is better in every way, but that would surely have resulted in a much more expensive eyepiece. The Swarovski 30XW will fit the Zen scope with excellent optical results, but it doesn’t engage the locking pin, so it may not be completely secure (once again, not recommended by Zen-Ray).

Eye relief measured 15mm from the eyecup, 21mm from the eye lens glass. AFOV was 59 degrees. That’s about 2 degrees more than the SE eyepiece measured the same way.

I notice that the Vortex Razor 30XW eyepiece shown on the Eagle Optics website looks very much like the Zen-Ray 30XW and has the same specs."
 

mayoayo

Well-known member
It's a 60 euros eyepiece, and not bad for that.. Henry really liked the vortex /zen copy of the swaro zoom, an eyepiece(the Swaro) that he has always regarded as one of the best.. So of course the 60 dollars flat field fell behind in the comparison.. He would have rather that it was the 30xSW.. And me too.. But I used this eyepiece in many scopes, included the Nikon ED50 (17.5x)and it was a very decent performer,and very very compact. I did a lot of video scoping with it..see if I can find and post some samples
 
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Ridge Walker

Well-known member
Thanks to for all the advice and suggestions. I've seen this eyepiece, 1.25" 18mm Orion Epic 2 - BST Starguider ED 60 Degree FOV. Also sold under quite a few names. Is on eBay £43.99. gives me around x27. The seller says it give a good flat field. Edge to edge sharpness. Thoughts on this eyepiece please. BTW My scope obviously is an OEM. I have found one like it with the exact same zoom eyepiece. An Orion Grandview 20-60x80 Zoom Spotting Scope, The ED version uses 1.25 eyepieces and has a locking ring.
Cheers
 
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mayoayo

Well-known member
BST Explorer/starguider dual ED, again many brands sell this eyepiece, is also a pretty good eyepiece for the price.. Has Been reviewed many times in these forums. I have the 12mm and I think is a very good eyepiece and a bargain.. They have a Barlow element in the barrel, so I think they are the same body with variations of the Barlow element..
 

Ridge Walker

Well-known member
BST Explorer/starguider dual ED, again many brands sell this eyepiece, is also a pretty good eyepiece for the price.. Has Been reviewed many times in these forums. I have the 12mm and I think is a very good eyepiece and a bargain.. They have a Barlow element in the barrel, so I think they are the same body with variations of the Barlow element..

Cheers for that info. It could have took me awhile finding the reviews on here. Just bought the 18mm, I think that will be ok for some digiscoping. Give an opinion when I get it

Thanks again and all the others for their help :t:|=)|
 

Tringa45

Well-known member
Europe
The off-axis performance is OK, but not in the same class with the premium wide field astronomical eyepieces I have on hand for comparison (14mm Pentax XW, 19mm Televue Panoptic)

Joachim,

I have never really understood the good reputation of the Televue Panoptics.
I believe they are all a scaled design and also own the 19 mm version. It has oodles of pincussion distortion and quite significant astigmatism.

John
 

jring

Well-known member
Joachim,

I have never really understood the good reputation of the Televue Panoptics.
I believe they are all a scaled design and also own the 19 mm version. It has oodles of pincussion distortion and quite significant astigmatism.

John

Hi John,

I have to admit that I have looked through real Panoptics only quickly at telescope meetings or in the club...

I do own a few 68mm ES EPs (which supposedly are Panoptic clones) and those I have or had (40mm, 16mm and 24mm which I sold for a 24mm 82 deg ) were not too shabby... we used them in the 16" f4.5 dobs of a friend and they worked nicely in there (and of course in all my slower scopes).

Joachim
 

henry link

Well-known member
Joachim,

I have never really understood the good reputation of the Televue Panoptics.
I believe they are all a scaled design and also own the 19 mm version. It has oodles of pincussion distortion and quite significant astigmatism.

John

Hi John,

I'm surprised that you see astigmatism in the 19mm Panoptic. I just fished out my 20 year old 19mm and 22mm Panoptics from a drawer. I can't see any astigmatism at the field edge of either, whether using an artificial star or a target of vertical and horizontal lines. I do see oodles of pincushion distortion, so much that it causes negative angular magnification distortion at the field edge.

Henry
 

Tringa45

Well-known member
Europe
Hi John,

I'm surprised that you see astigmatism in the 19mm Panoptic. I just fished out my 20 year old 19mm and 22mm Panoptics from a drawer. I can't see any astigmatism at the field edge of either, whether using an artificial star or a target of vertical and horizontal lines. I do see oodles of pincushion distortion, so much that it causes negative angular magnification distortion at the field edge.

Henry

Hi Henry,

My mistake. It seems my memory has been playing tricks with me :-(.
I have just set up a squared pattern and could detect no astigmatism through the 19 mm Panoptic in either of my birding scopes.
I see field curvature through all astro eyepieces and assume that many dedicated birding scope eyepieces have field flatteners.
Perhaps you could throw some light on the factors influencing field curvature and why some astro eyepieces are unsuited to fast focal ratios.
Presumably the field curvature in two f/6 scopes of 60 mm and 120 mm aperture with 12 mm and 24 mm eyepieces for 30x magnification would be similar.

John
 

jring

Well-known member
Hi John,

field curvature is governed by the design of the scope and the focal length - not focal ratio!

So it is quite clear, why the 60mm f6 with 360mm focal length has a smaller Petzval radius and thus worse field curvature than a 120mm f6 scope (720mm focal length) of similar design (sure, if the small scope has a 4 or 5 element flatfield objective, it might be even better)

https://www.telescope-optics.net/curvature.htm

And if you know the objective design and focal length of your spotting scope, it is not very difficult to design an EP with a field flattener for that.

An astro EP on the other hand should ideally work with scopes of all focal ratios and focal lengths.
For focal ratios, we know from experience that that is not the case - and it is not due to field curvature but due to simpler eyepiece designs suffering pretty badly from a faster light cone while more complex designs can sometimes cope better. See the eyepiece ray-tracing diagrams of different EP designs - all at 10mm EP focal length and for an f5 objective - best start at the end for what it should look like in modern designs and the go back to older designs...

https://www.telescope-optics.net/eyepiece_raytrace.htm

Btw. for astro imaging there are separate field flatteners available, but they need to be adjusted for objective focal length by mounting them at a specific distance to the sensor.

https://www.teleskop-express.de/sho...attener-Bildfeldkorrektor---2--Anschluss.html

Joachim
 

Tringa45

Well-known member
Europe
Thanks for all that, Joachim. I think it's going to require a bit of digesting ;).
In the example I mentioned it's clear that the field curvature in the larger telescope will be numerically larger (flatter), but would it not be subjectively similar to the smaller scope at the same magnification?

John
 

Ridge Walker

Well-known member
BST Explorer/starguider dual ED, again many brands sell this eyepiece, is also a pretty good eyepiece for the price.. Has Been reviewed many times in these forums. I have the 12mm and I think is a very good eyepiece and a bargain.. They have a Barlow element in the barrel, so I think they are the same body with variations of the Barlow element..

Hi, some info please? I've just bought the Orion version. 18mm Epic 2 - BST Starguider ED 60 Degree. Second hand. £30 Gives Me around x28 What I've found is you cant all the circle edges, at one time even if you move your head slightly, Is this normal for a WA lens, or do I need to lower the Mag.? Scope's is a F6. The lens has an excellent wide view, and a flat field. It is sharp on any edge towards the next edge up or down for about 80% of the image. Not knowing much on the subject, tried to explain best I can
Thanks for any comments
 
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