Review of the Brunton ICON 25-50x 80mm Angled Scope (2 Viewers)

I just digiscoped a ruler through the ICON 25-50x zoom (set at 50x) and several other eyepieces with nominal focal lengths between 8mm and 9m, all mounted on the same telescope. The size of the ICON image was a close match to a 9mm Takahashi Abbe orthoscopic eyepiece. If the ICON zoom's shortest focal length is 9mm then the scope focal length is 450mm. However that depends on the accuracy of the TAK's focal length spec and whether the 50x magnification setting on the ICON scope is really exactly 50x.

jnielsen said:

Two months later with my straight Icon with 25x50 I am still not seeing excessive lateral color or sharpness problems. Perhaps I have a very good eyepiece.

My Zeiss Diascope 85 T FL with 20x75 zoom shows much more CA at powers below 40x than the Brunton.

Click to expand...

jnielsen,

Glad to hear you're enjoying your scope. I'm pretty happy with mine too, especially after changing the eyepiece.

I can't say for sure why we are reporting such different results for lateral color and close focus spherical aberration, but I doubt that either aberration in my scope is related to sample variation. I suspect we are just using different evaluation methods and applying different standards.

Henry

Henry I would of just sent my 20-60x80 straight Brunton Icon spotter back to Botach after doing a "short" distance resolution test of it and the 80 not beating out my Nikon 60ED at short distance if not for you posting about this problem . When looking close I really didn't notice the lack of "sharpness" so much, just testing it a short distance is when I noticed it. As for the lateral color , not saying there isn't any but I am not real sensitive to CA. I am ok with the Icon spotter, but I still wish it was a Nikon 82mm Fieldscope. I have quite a few of the eyepieces. I can use these with the little 50ED.

Need Advice Positioning non-native Eyepiece Mount

Have Brunton Icon.
Messing with it...
My area of expertise is precision machining. All my raw materials are opaque. Now I'm fiddling with things that re-direct light... and I'm in need of advice.

• Have determined that a Swarovski clone zoom (Vortex Razor 20-60) will work without focus limitations. (thank you gcole for lending me the eyepiece which made this assessment possible)

• Have also determined there is ample material in the removable Brunton aluminum bayonet boss to allow boring it out, and grafting in a faithful precision machined Swarovski clone female bayonet receptacle.

• Confident enough in this project that a Swarovski 25x-50x Wide angle zoom eyepiece is on its way here as the primary replacement eyepiece for this scope.

• There is sufficient range of focus at and beyond infinity, that the eyepiece can be positioned fore and aft to a considerable degree.(Of course this has an effect on the minimum focal distance.)

• When the preliminary test eyepiece (Vortex Swaro clone) is as far forward as is feasible, it will focus as close as roughly 15 ft. That minimum focal distance gets shorter the further the eyepiece is positioned away from the scope body, until at some point the ability to focus to infinity becomes tentative.

• Not sure what if any effect the above variations have on actual magnification range.

Here's my primary question/concern;

Is there a rule of thumb, or fundamental principle which one should lean towards or strive for when positioning the eyepiece during fabrication of the new bayonet mount? i.e.,

• Should it be as close to the scope body as possible?

• Should it be as far away as possible?

• Should it be mid-stream with similar range of extraneous focal ring turn beyond infinite and minimum?

• Are there trade-offs for either extreme with respect to key performance criteria such as CA, FOV changes, contrast, etc.?

Unfortunately I do not have a way to adjust the position incrementally while observing the eyepiece performance. All the above assessments were made holding the eyepiece by hand in the back yard focusing on Venus. So any advice received will be priceless in imparting awareness of pitfalls I am oblivious to as an optics novice. :h?:

Ziabeam,

I would try to position the new eyepiece so that it duplicates the current position of the ICON eyepiece's focal plane at the back of the scope body. You'll know you're there when the new eyepiece is positioned so that it provides the same closest focus distance as the ICON eyepiece. If you have the space, moving the eyepiece a little closer in won't hurt anything, but it isn't desirable to move the eyepiece back. That increases vignetting toward the edge of the field from the prism at low magnification. Also, if you should ever want to make a adapter to go from female Swarovski bayonet to 1.25" eyepiece tube the extra in focus required if you move the eyepiece focal plane back will limit the eyepiece choices that can reach infinity focus.

Henry

Thank you Henry.
The Swarovski is due in on Friday.
Favoring forward sounds like good advice, and good to know about the vignetting as it moves away from the scope body, this is why I asked and thanks a bunch for the expert tips !!.
Speaking of the 1.25" adapter, it is still my intention to fashion one for the stock Brunton bayonet. Will let you know when I have built a few in case you are still interested.
More soon
Z

Ziabeam said:

Speaking of the 1.25" adapter, it is still my intention to fashion one for the stock Brunton bayonet. Will let you know when I have built a few in case you are still interested.
More soon
Z

Click to expand...

I definitely still want one.

Henry

I would love to have a 1.25" adapter for the Brunton as well. I bought gcole's scope with the Pentax XW20 and it's fantastic.

Mark

Astronomy Eyepiece Adapter

BinoBoy said:

I would love to have a 1.25" adapter for the Brunton as well. I bought gcole's scope with the Pentax XW20 and it's fantastic.

Mark

Click to expand...

Got the 25x-50x Wide Angle Swarovski on Friday, to compare against the 20x-60x Vortex, and Brunton Icon eyepiece. All 3 eyepieces had complete range of focus in the Brunton Icon body, although the two Swaro bayonet type eyepieces (Vortex being a Swaro clone) required positioning by hand. Because the Swarovski came perilously close to the "wall" of infinite focus, I duplicated all tests with and without the bayonet housing installed in the Brunton scope body. This allowed the Brunton to get 5/16" closer to the prism, and both the Swaro and Vortex to get 1/2" closer giving the Swarovski an enhanced opportunity to compete, also reducing any likelihood for vignetting as suggested by Henry. The overall performance of the eyepieces did not change much with the bayonet boss removed, though the Swaro did gain a little respect, it still faltered much to my surprise. Perhaps there are key design factors in a Swarovski scope body, which the Swarovski eyepiece is more adaptable to.
Weather cooperated and was able to do indoor and outdoor tests. Tests were performed viewing intricate tree buds at 70 yards against both overcast and blue skies. Tree lichen mottled bark deep in wooded lots at 150 yards, with more distant illuminated trees visible in meadows through portals in the woods. Distant (400+ yds) tree tops against overcast and blue skies. Also viewed a pleasantly blue and brown porcelain jug, with micro cracked glaze at 17 yds, as well as the text on a house power meter at 15 yds. Viewed sun glazed/cracked PVC sheaths on power pole guy-wires at 18 yds. All observations were made from a bench in my back yard, carefully changing eyepieces countless dozens if not hundreds of times trying to arrive at an impartial determination in every respect. The vast majority of my opinions were repeatable, and increasingly certain in my mind, sufficiently so that my final determination is one that I hope to never second guess, since two of the three eyepieces will be returned.
I am no expert on these matters, so my findings are very primitive, similarly the description will be primitive;

• Indoors (at very close distances) the high dollar Swaro looked most promising, with the least detractors at close distance under fluorescent lighting. Text on wall charts was very sharp. The Brunton and Vortex were a close second, with a slight edge to the Vortex on sharpness. My Brunton eyepiece showed nothing near as bad as the results shown in HenryLink's photos, yet still somewhat 'amiss' at 14 feet.

• Outdoors the Vortex 20-60 won the resolution contest by a wide margin over the Swaro, narrowly beating the Brunton eyepiece during overcast conditions, though the Brunton easily matched it in bright conditions.

• The Brunton trounced the other 2 eyepieces in the low light performance, which was surprising. The Swaro beat the Vortex which was a distant 3rd.

• The perimeter of image distortion was most noticeable on the Brunton (worst of the 3) outdoors at low power focused on close-up objects. In this case a bolt head, viewed on a metal building wall at an oblique angle. Being at an oblique angle the center-to-edge focus variation was more pronounced, however focus correction completely eliminates the edge distortion (vignetting?) at the edge compensated for on the Brunton. The Vortex won this contest, while the Swar showed only slight issues, barely noticable

• Despite the lack of wide angle, the Vortex looked better than the Swaro on many levels that are difficult to describe. The Swaro's most notable edge over this particular Vortex was low light level performance, and wider angle view. Wish I'd had a wide angle Vortex to compare to the Swaro. If the wide angle Vortex (25-50) even remotely competes with the Swaro wide angle performance, and equals the 20x-60x Vortex I had on hand in all other respects, it would easily be the equal of, if not significantly superior to the Swaro.

In summary, the Brunton Icon eyepiece is a keeper. No it is not perfect, and it is frustrating to use when a mirage is boiling, but most if not all eyepieces are. One caveat to this complaint is the Brunton sees mirage with remarkable clarity, which is VERY VERY handy for reading wind velocity at the rifle range.

Footnote,
BinoBoy since the Brunton eyepiece is staying, this should streamline the astronomy eyepiece adapter project for it.
Might take me a while, but it will happen.
Did your Brunton/Pentax XW20 marriage allow you to remove the epoxied in eyepiece, with the Brunton bayonet boss intact?

On a similar note...

As mentioned earlier, I recently binged on several new scopes, and learned from research the Pentax PF65ED has its share of disheartened owners (me included) who learned the Baader MKIII won't focus to infinity in it. While I have the Vortex and Swarovski eyepieces in hand it seems worthwhile to explore whether or not either of them would do the trick, offering better results than the low end Pentax zoom eyepiece, in a much smaller package than the coke can sized high end Pentax zoom (which also achieves high enough magnification to exceed practical use in the PF65ED). During assessment of the Swaro and Vortex in the Brunton, the Swarovski seems most tenuous of the two, due to being perilously close to failing to achieve infinity focus if too far back (same fate the Baader suffers), while the Vortex achieved the same feat with copious room to spare.

There are two reasons this might be a good idea, and similarly, the same two factors might make this a fruitless endeavor.

First consideration;
Vortex offers numerous HD eyepieces at VERY reasonable prices, which conceivably could be converted to 1.25" astro type mounts. Proposed adaptation involves replacing the bayonet portion of the eyepiece which involves removing 3 screws, and replacing it with an uber simple 1.25" astro-type mount. Problem is I cannot find any pictures of the other Vortex eyepieces to see if their bayonet end of the eyepiece is a similar 3 screw attachment, or a homogenous part of the fixed power eyepiece, which would render them incompatible to the same conversion approach... Anyone have a Vortex fixed power variant they can peek at? Does it have 3 screws holding the bayonet on the back side? BTW don't remove it unless you have a purge cabinet or you risk depleting the nitrogen or argon charge.

Second Consideration;
We all know that a variety of accessory Vortex eyepieces can be readily obtained. (the ones eluded to in the first consideration whose bayonet adaptability is in question) But I see no availability of the zoom eyepieces no matter how hard I search. Does anyone know before I call Vortex if the zoom eyepieces are readily available separately?

Hi Ziabeam,

I don't know if the XW20 can be removed from my Brunton. Perhaps gcole can answer that.

Mark

Pictures of the bayonet flange of the Vortex 18/23x HD eyepiece

Ziabeam said:

As mentioned earlier, I recently binged on several new scopes, and learned from research the Pentax PF65ED has its share of disheartened owners (me included) who learned the Baader MKIII won't focus to infinity in it. While I have the Vortex and Swarovski eyepieces in hand it seems worthwhile to explore whether or not either of them would do the trick, offering better results than the low end Pentax zoom eyepiece, in a much smaller package than the coke can sized high end Pentax zoom (which also achieves high enough magnification to exceed practical use in the PF65ED). During assessment of the Swaro and Vortex in the Brunton, the Swarovski seems most tenuous of the two, due to being perilously close to failing to achieve infinity focus if too far back (same fate the Baader suffers), while the Vortex achieved the same feat with copious room to spare.

There are two reasons this might be a good idea, and similarly, the same two factors might make this a fruitless endeavor.

First consideration;
Vortex offers numerous HD eyepieces at VERY reasonable prices, which conceivably could be converted to 1.25" astro type mounts. Proposed adaptation involves replacing the bayonet portion of the eyepiece which involves removing 3 screws, and replacing it with an uber simple 1.25" astro-type mount. Problem is I cannot find any pictures of the other Vortex eyepieces to see if their bayonet end of the eyepiece is a similar 3 screw attachment, or a homogenous part of the fixed power eyepiece, which would render them incompatible to the same conversion approach... Anyone have a Vortex fixed power variant they can peek at? Does it have 3 screws holding the bayonet on the back side? BTW don't remove it unless you have a purge cabinet or you risk depleting the nitrogen or argon charge.

Second Consideration;
We all know that a variety of accessory Vortex eyepieces can be readily obtained. (the ones eluded to in the first consideration whose bayonet adaptability is in question) But I see no availability of the zoom eyepieces no matter how hard I search. Does anyone know before I call Vortex if the zoom eyepieces are readily available separately?

Click to expand...

Here is a few pic's of Vortex Razor HD 18/23x long eye relief eyepiece .... gwen

Pentax XW20 Removal From The Brunton

BinoBoy said:

Hi Ziabeam,

I don't know if the XW20 can be removed from my Brunton. Perhaps gcole can answer that.

Mark

Click to expand...

I do not think so, without doing harm to the eyepiece or scope ocular port. I used the "Liquid Nails" silicone formula & I did not skimp on the amount I used. I did a test on two very large metal washer that were partially overlapped prior to the eyepiece attachment. When in a bench vice held securely, I could not break the two apart using a hammer or vice grips .... gwen

Ziabeam,

if you are unable to purchase the Vortex zooms as separate items you might want to check out the Zen-Ray zooms. I know the Zen-Ray 20-60x is the same Swarovski clone as the Vortex 20-60x. The Zen-Ray 25-50x is not a clone of the Swarovski 25-50x, but it and the Vortex 25-50x may be the same eyepiece (I haven't compared them), since the 20-60x and 30x Z-R and Vortex eyepieces are identical.

I have a very low opinion of the Pentax 6.5mm-19.5mm zoom that comes with the Pentax 65mm scope. My unit is the worst zoom eyepiece I have tried (i haven't evaluated any of the really cheap ones). IMO the Nikon 20x-60x MCII is a much better eyepiece and covers a similar focal length range (7mm-21mm) with similar FOV.

Henry

Not being able to remove the XW20 from my Brunon is not a problem.

I ended up with three of the Burntons. A straight one I bought from Botach with the 25-50X and two angled ones that I bought from gcole. One has the 25-50X and the other the XW20.

So, if I had an adapter that just bayoneted on the Brunton, I'd just use it on the two unmodified ones.

GCole your Vortex loaner eyepiece is like a one-club-golf-bag... I'm determined to try it in every hole on the course. Might even find it a home and have to beg you to sell it to me. It is a lot of eyepiece for the money, and I'm determined to try and find a billet for it, unless of course you decide the billet I find for it is best served in one of your scopes. Until we decide thanks again for entrusting me with it.

BinoBoy glad to hear you won't have to pound that Pentax out of the Brunton to make use of an adapter... would hate to be an unwitting accomplice to that

HenryLink it seems a reasonable chance that the wide angle ZenRay zoom would have the 3 screw attached bayonet, since the photo of the 20-60 Z-R appears to. Hoping the wide angle Z-R has similar optical quality to the comparable (respectable) Vortex. Research seems promising, and YES from what I've read, the Pentax low end zoom is not spoken highly of most places.
By the way... Is the Nikon you spoke of already 1.25" astro-type as the pictures suggest?

Update... the design of a Brunton specific astro adapter may require titanium alloy material selection, due to much less favorable design envelope when compared to the Swarovski bayonet receiver and its resulting adapter. The popular Swarovski astro adapter envelope lends itself well to the use of an aluminum, while the Brunton's envelope has much less room both radially and axially for inherent stability and strength if aluminum were used (too thin and abbreviated at the bayonet fingers' depths).
Titanium alloy won't significantly increase cost though, since small quantities per unit are in play (not like the linear requirements when changing a whole bicycle frame material), and anodizing can be bypassed since titanium alloy does not need surface reenforcing like softer aluminum.

Just thinking out loud.

More thinking out loud....
If the Nikon line Henry pointed out is viable, and already has 1.25" astro-type stems ???, then that sensibly dampens the notion of adapting Vortex or Zen-Ray zoom eyepieces for use in the Pentax PF65, unless only the Vortex/Zen-Ray would achieve infinite focus, coupled with exemplary performance in other key respects. Also noteworthy is the fact that gcole's photos seem to indicate the fixed variants (absent '3-screw-upgradeable bayonets) are not suitable for converting to 1.25".

At least the Brunton 1.25" adapter still seems plausible.

I'm just warming up my thinking cap. Never mind the babbling.

Ziabeam,

Please don't take my mention of the Nikon zoom as an endorsement. I only meant to say that its an eyepiece comparable in focal length range and FOV to the Pentax zoom, but optically superior. The FOV is not wide, eye relief is short and it's not widely available anymore. It does not come with a 1.25" tube. You would need to make one to fit its screw mount (which would also fit the fixed Nikon eyepieces).

I've only seen a prototype of the the Zen-Ray 25-50x, so I don't know how good the production units are. All the Zen-Ray eyepieces have the same bayonet derived from the Swarovski design that the Vortex scopes use, but there are small differences in the dimensions of the bayonets.

Optically, I much prefer the Baader Hyperion zoom to anything else under discussion here. It does not compromise the axial performance of any scope and on the ICON it yields a more useful range of magnifications than the Swaro or Vortex/Z-R 25-50x zooms (about 18.5-56x vs 24-48x) and the FOV is nearly as wide over the same range.

Henry

Baader Zoom/Burgess 1.9 Corrector Combo ?

henry link said:

Ziabeam,

Please don't take my mention of the Nikon zoom as an endorsement. I only meant to say that its an eyepiece comparable in focal length range and FOV to the Pentax zoom, but optically superior. The FOV is not wide, eye relief is short and it's not widely available anymore. It does not come with a 1.25" tube. You would need to make one to fit its screw mount (which would also fit the fixed Nikon eyepieces).

I've only seen a prototype of the the Zen-Ray 25-50x, so I don't know how good the production units are. All the Zen-Ray eyepieces have the same bayonet derived from the Swarovski design that the Vortex scopes use, but there are small differences in the dimensions of the bayonets.

Optically, I much prefer the Baader Hyperion zoom to anything else under discussion here. It does not compromise the axial performance of any scope and on the ICON it yields a more useful range of magnifications than the Swaro or Vortex/Z-R 25-50x zooms (about 18.5-56x vs 24-48x) and the FOV is nearly as wide over the same range.

Henry

Click to expand...

As to Henry's comment of the Baader Hyperion zoom .... After reading Medinabrit's comment here in Dec. 2009 saying that the Baader zoom will work in the Pentax 65mm when the Burgess 1.9x Binoviewer is used, I purchased a couple awhile back thinking they would come in handy if & when I ever wanted to use them in a binoviewer or with the Baader zoom. I never ended up using it in a binoviewer or the Baader zoom but I can say that when I used it with the XW20 Pentax eyepiece in my Pentax 65 EDAII it gave a very sharp/clear view with just enough magnification increase not to show any significant loss in brightness or clarity. Burgess states the Mag. change will vary depending on the eyepiece/focal range of the scope used. With the Burgess 1.9x corrector I never found the need to use the XW14 eyepiece again. With the Burgess corrector & the XW20 eyepiece combo, it is like having two eyepieces in one. Simply screw on the Burgess corrector to the end of the Pentax XW20mm eyepiece & you turn the 19.5x XW20 eyepiece into a mid to high power eyepiece giving what seems to be close to what the 28x XW14 Pentax gives. What makes it even better is that Burgess sells this little jem(small in size) for only $10. I mentioned all this because when " Ziabeam " comes up with a adapter for the Brunton Spotter, there will be the possibility of using it with the Baader zoom & if there is a focus problem one could try using it with the Burgess Binoview corrector. .... gwen