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"pinpoints stars" at giant binoculars - really ideal points?

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#1 barti14

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Posted 11 July 2021 - 06:46 AM

I have Bushnell Legend M 8x42 and Nikon Monarch 5 16x56. For both stars 2-4 mag are really nice points on axis.

At Nikon maybe not ideal points but very small regular circles. Anyway nice view of stars.

 

I saw stars at Argus and APM 25x100 and old TS BA8 20x110 described as best corrected from all BA8 series.

All 3 big binos showed stars with small "tails" changing direction when we moving eyes up-down around eyepices (see pic below). I painted it little bigger than in real to described situation.

 

sharp.JPG

APM was the smallest tails but still easy visible.

My collegue - who saw many binos - said it is normal at giant binos.

 

But Nikon stars don't have it - any "tails" on medium bright stars. 

He said propably Nikon has additional correction.

 

How it looks like at your eyes? Maybe we have bad binos or our eyes are not perfect? smile.gif

Do you have really ideal points?

 



#2 wrvond

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Posted 11 July 2021 - 07:00 AM

Can’t say I’ve ever really noticed. I use my binoculars primarily for planetary observations and my telescopes for the stars.



#3 ArsMachina

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Posted 11 July 2021 - 08:48 AM

When I still had my APM 25x100 ED the stars did not have tails.

With the APM 150SD it is the same.

 

Jochen


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#4 duck2k

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Posted 11 July 2021 - 12:09 PM

My 127’s have “tailed” stars, I do not use my glasses when observing. I tried them with glasses on, same result. I think it is my eyes. Other objects look good: galaxies, M57, M27, certain open star clusters, and globulars. The tails are usually on the medium bright stars. I still think it is my eyes. I will be getting a prescription check up next month.

#5 pat in los angeles basin

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Posted 11 July 2021 - 12:21 PM

If it was the glass, would the tail not stay in relation to the eyepiece view and if in the eye would it not follow your eye orientation?

                                                                                                                                             Regards, Pat



#6 Fiske

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Posted 11 July 2021 - 01:01 PM

Comparing views side by side between my TV-101 and binoculars, the APO refractor is sharper without question. Whether I am wearing glasses or not. Stars are pinpoint in the telescope. No tails or artifacts. With binoculars the stars aren't quite as sharp.

 

When I am focusing a binocular and looking through one side or the other side only, tails and artifacts are more apparent. In fact, one of the things I concentrate on when focusing is to minimize artifacts. When looking through both sides simultaneously, the effect is no longer apparent, I believe because neurologically it's being filtered out. Also, it is more of a factor on brighter stars. Say stars 5th magnitude and brighter. Where stars 6th magnitude and fainter are far less likely to show the effect.

 

Eye position is more critical with binoculars than with the telescope, which naturally follows from working with two optical assemblies instead of one.

 

Finally, what seems obvious to me, though I'm not sure it is widely accepted, is that the complexity of binocular prism assemblies unavoidably introduces optical issues, however slight they might be. The TV-101 has an excellent quality mirror diagonal. It's a single, first surface reflection. And the impact on the image is far less significant than multiple reflection/refractions of a binocular roof or porro prism. It just stands to reason. Amici prism diagonals (used with telescopes for a correct image) are well known to introduce spikes on brighter stars. Even the best quality prisms exhibit the issue (though to a lesser degree than lower quality/cost Amici diagonals). And the same issue is involved -- the complexity of a prism diagonal compared with straight through optics or a mirror diagonal.

 

Fiske


Edited by Fiske, 11 July 2021 - 01:02 PM.

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#7 Jon Isaacs

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Posted 12 July 2021 - 05:13 AM

Comparing views side by side between my TV-101 and binoculars, the APO refractor is sharper without question. Whether I am wearing glasses or not. Stars are pinpoint in the telescope. No tails or artifacts. With binoculars the stars aren't quite as sharp.

 

 

:waytogo:

 

The TeleVue TV-101 is a very special 4 inch F/5.4 four element apochromatic refractor. It's a "modified Petzal" which means it has a front two element ED objective and a rear two element ED field flattener/focal reducer that results in a very flat field that is corrected for the various aberrations, coma, field curvature, astigmatism etc.  The current version, the NP-101 IS is $4000 bare bones.  

 

In addition, one needs eyepieces that are corrected for off-axis astigmatism, ideally these are also TeleVue eyepieces.  The 31mm Nagler in a NP-101 offers an essentially perfect 4.5 degree field at 17.4x.  The 31mm Nagler weighs a kilogram and costs $650.  Add a diagonal and that's a $5000 view.  

 

There are binoculars with field flatteners and very good eyepieces, they are expensive and are still compromised to some extent one way or another when compared to the TV-101/NP-101.  

 

But the telescope experience is different from the binocular experience, at least in my experience. :)  With a telescope, it's eyepiece is fixed and unconstrained by the other eye so moving the eye/head around the field of view is easily done and commonly done, this means the edge of the field performance is easily seen.

 

With binoculars, one tends to keep the eyes centered and move the binoculars around around, this means the edge of the field is always in the peripheral vision and aberrations like field curvature and off-axis astigmatism are much less apparent.  

 

Jon


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#8 Fiske

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Posted 12 July 2021 - 07:39 AM

Jon,

 

Agreed on every point and well spoken. smile.gif

 

However, tails and artifacts on brighter stars can be seen in the center of the field of view with larger binoculars. The issue isn't specifically about edge performance. The binocular observing experience is different from observing with an APO refractor, with its own advantages and disadvantages. Even if a binocular telescope were constructed from OTAs like the NP-101, not only would the cost easily exceed $10,000, and result in an instrument weighing in excess of 50 pounds (guessing), with a length of 32 inches or more, BUT the added complexity of the prism assemblies would still compromise the optical performance to some extent. 

 

To me, it's a matter of what is reasonable to expect from binocular performance versus an APO refractor. The 100XL-SD is a $2900 instrument, with two 100mm optical assemblies, plus dual 45 degree porro prisms, weighing only 12 pounds and only 22-inches in length. It is a marvel of engineering and a delight to observe with. The optical performance is remarkable, given the instrument's complexity and cost.

 

Fiske

 

PS: At $470, the Oberwerk 25x100 Deluxe is a shockingly good value considering the views it provides. Less than the cost of the Nagler 31mm T5 eyepiece! lol.gif


Edited by Fiske, 12 July 2021 - 07:42 AM.

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#9 Jon Isaacs

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Posted 12 July 2021 - 07:58 AM

However, tails and artifacts on brighter stars can be seen in the center of the field of view with larger binoculars. The issue isn't specifically about edge performance.

 

 

In general, I find on-axis binocular views reasonably sharp.  The observer's eyes can be important here.. 

 

Jon


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#10 Fiske

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Posted 12 July 2021 - 08:03 AM

Agreed, Jon. As the size of the binocular increases, however, so do the optical challenges. wink.gif

 

But you make a good point. I'll do some comparisons with uncorrected (slightly astigmatic vision) and my fully corrected vision paying particular attention to star tails. grin.gif

 

Thank you!

 

Fiske


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#11 barti14

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Posted 13 July 2021 - 05:13 AM

Thanks for replies!

Why I asking? For few years I used refractor SW102/500 and small binos 7x35, 8x42 and finally mentioned Nikon 16x56. All those stuff give very nice consistent stars on-axis. Pleasant views like by naked eyes.

But views from 3 different 25x100 binos destroy my romantic perceptions and moved to ground smile.gif

 

I tried to sketch it again and keep scale (I'm not good painter wink.gif )

stars.JPG

If we define ideal pinpoint star like first dot - than Nikon at 16x gives second view: bright, slightly bigger point with very small, regular and equal spikes around. Anyway still very nice view.

But all 3 pcs of 25x100 showed me stars deformed (like 3rd below) with kind of tails - bigger or smaller - depends on bino, star brightness in its position on AFOV.  

It's look like giant binos have different category. All 3 constructions had similar stars view but it was far from nice regular shape. 

 

Like Fiske wrote, after good align by both eyes those deformation compensate each other gives better view than by one eye. I could find Altair (0.9 mag) in Nikon as almost regular point. But when I moved eyes slightly it showed me tail in one direction and deformed shape.

For giant binos good positioned both eyes only helps partially. Better should be description "reasonably sharp" than pinpoints.

I try to guess why. Maybe degradation by prisms growing square or more due to magnification?

 

For last year I lived with idea to buy big bino for review stars fields like by naked eyes but with such deformations I lost a fun little.. ehh...

Live with it or stay at 16x and save money for make a bino from two apo refractors ? smile.gif

 

 


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#12 ArsMachina

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Posted 13 July 2021 - 05:28 AM

Hi Barti,

 

it is not a problem of the size of the binoculars, it is a problem of their quality.

Most 25x100 binoculars are cheap chines achromats and one can not expect perfect optics from them.

 

If you want it better, you have to spend more money.

 

As told before I owned the APM 25x100 ED magnesium as "placeholder" until my 150mm binoculars arrived.

And that bino was optically perfect, even better than smaller "high grade" binoculars like Nikon or Fujinon.

But for the price of the APM 25x100 ED you can buy three pairs of regular 25x100 binoculars ...

 

Jochen


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#13 Fiske

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Posted 13 July 2021 - 06:23 AM

So this is where the wisdom of owning both an Oberwerk 25x100 Deluxe AND a 100XL-SD shines forth. grin.gif

 

I'll do some side by side comparisons between the two instruments and report my findings. 

 

Also, I will say that I am pleased with the 25x100 Deluxe -- for its price point it's a terrific value. Optically, I would not expect it to match the APM 25x100 ED MS (3x the price) performance, but it is certainly good enough to provide enjoyable views.

 

Details to follow. wink.gif

 

Fiske


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#14 wrvond

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Posted 13 July 2021 - 06:50 AM

So this is where the wisdom of owning both an Oberwerk 25x100 Deluxe AND a 100XL-SD shines forth. grin.gif

 

I'll do some side by side comparisons between the two instruments and report my findings. 

 

Also, I will say that I am pleased with the 25x100 Deluxe -- for its price point it's a terrific value. Optically, I would not expect it to match the APM 25x100 ED MS (3x the price) performance, but it is certainly good enough to provide enjoyable views.

 

Details to follow. wink.gif

 

Fiske

I'm with you. You'll not see me running out to replace my OB 28x110 binos any time soon!

IMG 4110

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#15 dufay

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Posted 13 July 2021 - 06:52 AM

My experience is similar to Jochen’s.

 

I currently own a Bresser ED 20x80 (same as the APM) and it gives pinpoint star shapes over most of the field of view. The view is very similar to what one would expect of an ED refractor at this magnification, but with better edge correction thanks to the flatteners. Conversely, when I had the 12x50 from the same series, I was never able to reach pinpoint stars, even in the central part of the field.

 

It appears you have been unlucky with your 25x100s, and lucky with your smaller binoculars.


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#16 astrokeith

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Posted 13 July 2021 - 08:56 AM

I am not surprised.

Smaller aperture binoculars are easier to design, easier to make, and are made in volume and by multiple manufacturers. So for a reasonable price one can expect good performance

Large aperture bins are like large aperture refractors - the cost rises very very much faster. They are going to cost even more than two refractors as we have to add prisms and an IPD adjustment mechanism.

 

When I bought my Miyauchi 100mm bins, about 15 years ago, I tested the EDs and the Fluorite APOs side by side. From memory in todays money the ED's would be about £4000 and the APO's £6000.

 

I could see some aberrations in the ED, none in the Fluorites. I was fortunate to then have the cash and bought the APOs. You cant buy them any more as the market at that price isnt sustainable I expect.

 

I still have them and enjoy them. Their only disadvantage is the non-standard eyepieces.


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#17 ihf

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Posted 13 July 2021 - 09:40 AM

barti14, do you need glasses and are you observing with glasses on? Or maybe you have extremely good vision? Are you very near or far sighted and observe without glasses? Also can you check each tube with each eye individually? It sounds like you tried 3 very different binos and saw the same effect in each of them. I would expect at least one tube to be good, so sample variation (which is high in Chinese optics) becomes somewhat less likely. I can see the difference between pinpoint stars and not with different eyepieces, but I am not bothered by imperfection. But that might be because my astigmatism keeps growing and I might be more accepting of fuzziness. Before you build your own tescope maybe give the Oberwerk 20x65ED a chance? It has two tubes at f/6 instead of f3.8 and is generally described as more APO like.


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#18 barti14

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Posted 13 July 2021 - 03:50 PM

Need to add I compared APM ED version, not normal. Sorry for not precise.

 

barti14, do you need glasses and are you observing with glasses on? Or maybe you have extremely good vision? Are you very near or far sighted and observe without glasses? Also can you check each tube with each eye individually? It sounds like you tried 3 very different binos and saw the same effect in each of them. I would expect at least one tube to be good, 

I don't use glasses and I have still very good vision. I found many situation when I saw more than others (like bus number from far distance, etc) and I'm good in sport shooting. Hate any dust on lenses and accept FullHD resolution only to max 21 inch monitors due to not sharp fonts. Yes, I'm difficult wink.gif

 

I consider my eyes flaws deeply but it should appear on 16x56 on bright 0-1mag stars easly (like 2-3mag at 100mm) - but not.

I checked both tubes by the same leading eye. I saw only very small differences in tubes. I can't remember about Argus as it was year ago. TS and APM tested this weekend togather.

 

My colleque owning TS has the same opinion like Fiske and astrokeith - only very good refractors have pinpoint stars. He said also it is only big and fast f/3,8 bino and I should accept this view.

 

Anyway I decided to return this bino and sent my opinion to APM. I hope I got unlucky unit as dufay and Johen could say.

 

Maybe I'm too demanding but from the other side I read many comments on forums: if you like stars from refractors you may be dissapointed the stars view from Newton..

This is only level of imperfections tolerance... :)

Thank you all!

 

 

 

 

 



#19 jprideaux

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Posted 13 July 2021 - 04:30 PM

Part of it is that more magnification also brings out optical flaws more and bigger binoculars typically have more magnification.   Then the quality pays a greater aspect.

 

To go big and good starts to cost a lot more money.

 

For example, even last night I was experimenting with the same refractor (AT92 APO) and my same eyeballs with various eyepiece setups including binoviewers with looking at the 2nd star in the handle of the big dipper which has a couple nice doubles. One option with a lot of glass involved (focal extender and binoviewers) did have some noticeable optical aberrations for the stars.  When I took that off (with the same telescope) and replaced it with a single ES 5.5mm 100 degree 2" eyepiece, I saw pretty much perfect pinpoint stars.  The main difference in my two setups were that the single eyepiece was designed for one specific purpose and was optically superior to the other set-up I did with cobbling together a focal extender along with a binoviewer to get something close to the same magnification.  So we do pay a price for the joy of using two eyes with the special ways we bend light to get both images just at the right place for both eyes at the same time.  If we pay the big bucks and get the very best high-quality set-up we pay in a different way but get better views.   Yes and at lower power, we can get away with more.


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#20 Rich V.

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Posted 13 July 2021 - 05:17 PM

 

When I bought my Miyauchi 100mm bins, about 15 years ago, I tested the EDs and the Fluorite APOs side by side. From memory in todays money the ED's would be about £4000 and the APO's £6000.

 

I could see some aberrations in the ED, none in the Fluorites. I was fortunate to then have the cash and bought the APOs. You cant buy them any more as the market at that price isnt sustainable I expect.

 

I still have them and enjoy them. Their only disadvantage is the non-standard eyepieces.

I purchased my Miyauchi Saturn IIIs from Kevin at Oberwerk about 15 years ago, myself. I think I got the last one available in the USA.  I wanted the option of higher magnification eyepieces than the 500mm fl Galaxy models provided.  The Saturns were $2600. back then with one eyepiece pair included along with a hard case.  

 

Over the years, I've been able to spend time comparing them with several other 100mm BTs.  Because of the longer focal length achromat doublet of the Miya Saturns, they put up tighter, less color fringed stars than the APM 100mm f5 Miya-clone and the Oberwerk BT100mm f6.  They are exceeded by the APM 100 ED f5.5, though.  Between the achromats, f ratio seemed to go hand in hand with how pinpoint the stars were.  The APM f5 had the most fringing and largest stars, followed by the Obie f6 with the f7.5 Miyas showing the finest star points.  The APM f5.5 EDs put up even tighter stars with less CA than the Miyas but I never compared the two above 75x.  I find the Miyas at 150x show enough CA with some SA on stars where I can't bring them to finest points or show a clear diffraction pattern like my scopes do easily. 150x is likely pushing even a 100mm ED bino too far, IMO, with a tiny 0.66mm exit pupil.  Still, at 150x with the Miyas, I've watched Jupiter's lunar shadow transits, seen the GRS, four Plato craterlets and five of Saturn's moons with them.  Not bad for a achromat BT; I suppose that's why I've stuck with them.

 

Rich


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#21 Fiske

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Posted 13 July 2021 - 05:18 PM

If skies are clear tonight I have a few things on my observing agenda. First up is some side by side comparisons between the OB 25x100 Deluxe and the 100XL-SD. I'll put Pentax 20mm XW eyepieces in it for that comparison, which is 28x in the 100XL versus 25x in the Deluxe. It will be an interesting comparison. I am familiar enough both instruments that surprises are not likely, but it might be helpful to record detailed descriptions of both views.

 

The Pentax 5mm XW eyepieces arrived yesterday (112x in the 100XL), and I'm going to give them a try on the Double Double in Lyra. With the 7mm XW (82x in the 100XL) I was able to resolve the E2 components, but not the E1 components. At least not more than about 30% of the time. I am hoping, more or less expecting, that both E1 and E2 components will be resolved at that magnification. Kevin rates it to 140x, so the 112x should be well within its capabilities. Also planning to revisit a few other closer doubles (at least for BTs wink.gif ) 70 Oph (4.19/6.17 6.7" pa 121*) and Rho Hercules (4.51/5.40 4.1" pa 321*).

 

I own two APM binoculars -- 12x50 ED MS and 16x70 ED MS -- both fine instruments. I decided not to also purchase the 25x100 ED MS for a few reasons. First, while the optical performance would be an improvement, the visual difference between it and the OB 25x100 Deluxe for deep sky observing would be subtle. Secondly, APM has some QC issues and their customer support is not on a par with Oberwerk. Not in the USA, anyway. I more or less decided to put that money toward the 100XL-SD. I'm really looking forward to my first lunar views with it. grin.gif

 

Depending on conditions, I might also get out the TV-101 for some side by sides on the double stars. Again, I more or less know what to expect. A good quality APO refractor is flat out sharper than good quality binoculars. My sense is that if side by side comparisons are not being done, neurologically it is difficult to quantify something like "sharpness" of stellar images. The differences are just much more apparent when looking through the instruments side by side to immediately compare the views.

 

Fiske


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#22 Fiske

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Posted 13 July 2021 - 05:24 PM

I purchased my Miyauchi Saturn IIIs from Kevin at Oberwerk about 15 years ago, myself. I think I got the last one available in the USA.  I wanted the option of higher magnification eyepieces than the 500mm fl Galaxy models provided.  The Saturns were $2600. back then with one eyepiece pair included along with a hard case.  

 

Over the years, I've been able to spend time comparing them with several other 100mm BTs.  Because of the longer focal length achromat doublet of the Miya Saturns, they put up tighter, less color fringed stars than the APM 100mm f5 Miya-clone and the Oberwerk BT100mm f6.  They are exceeded by the APM 100 ED f5.5, though.  Between the achromats, f ratio seemed to go hand in hand with how pinpoint the stars were.  The APM f5 had the most fringing and largest stars, followed by the Obie f6 with the f7.5 Miyas showing the finest star points.  The APM f5.5 EDs put up even tighter stars with less CA than the Miyas but I never compared the two above 75x.  I find the Miyas at 150x show enough CA with some SA on stars where I can't bring them to finest points or show a clear diffraction pattern like my scopes do easily. 150x is likely pushing even a 100mm ED bino too far, IMO, with a tiny 0.66mm exit pupil.  Still, at 150x with the Miyas, I've watched Jupiter's lunar shadow transits, seen the GRS, four Plato craterlets and five of Saturn's moons with them.  Not bad for a achromat BT; I suppose that's why I've stuck with them.

 

Rich

Yeah. I'm thinking the 5mm Pentax at 112x is about as far as I'm going to go with the 100XL-SD.

 

lol.gif lol.gif lol.gif

 

Here is a something I am wondering about. A little OT so please forgive. In my innocence I imagined narrowband or OIII filters could be attached to the eyepieces for use with the XL binoculars. This doesn't work, unfortunately, because the instrument cannot be focused with the additional eyepiece extension. However, the threading on the Pentax XWs is designed in such a way that filters could be threaded inside the eyepiece extension tubes so that they would not increase the overall length. I'm not sure where such filters could be obtained. Or even if they are available.

 

Fiske


Edited by Fiske, 13 July 2021 - 05:25 PM.


#23 jprideaux

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Posted 13 July 2021 - 06:02 PM

Yeah. I'm thinking the 5mm Pentax at 112x is about as far as I'm going to go with the 100XL-SD.

 

lol.gif lol.gif lol.gif

 

Here is a something I am wondering about. A little OT so please forgive. In my innocence I imagined narrowband or OIII filters could be attached to the eyepieces for use with the XL binoculars. This doesn't work, unfortunately, because the instrument cannot be focused with the additional eyepiece extension. However, the threading on the Pentax XWs is designed in such a way that filters could be threaded inside the eyepiece extension tubes so that they would not increase the overall length. I'm not sure where such filters could be obtained. Or even if they are available.

 

Fiske

All I've seen so far are the 1.25" filters that screw on the end of the eyepiece that do make it a few mm longer.

 

Perhaps ask Kevin at Oberwerk if he knows of anything.  



#24 Rich V.

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Posted 13 July 2021 - 06:09 PM

Yeah, you're pushing up against the short backfocus that BTs have; even a filter's 1/4" depth prevents infinity focus on the Obies, huh? 

 

I just looked at one of my XWs and see there could be enough room to drop the filter glass without the threaded holder up inside the barrel.  Looking at a Lumicon UHC filter, I see the glass is held inside the threaded holder with a lock ring.  With the lock ring unscrewed, the glass comes out of the holder.  You might then drop the filter glass into the XW barrel and the threads of the lock ring you removed from the filter would screw into the XW's same pitch threads to hold it in.  

 

I used a similar trick with my Miyas which have a proprietary 1.3" barrel.  I put thin strips of electrical tape around the outside of standard 1-1/4" filters and they would press fit up inside the barrels with plenty or room to reach focus.  That was easier since no filter disassembly was required.

 

I still found even a UHC was too dark for the smallish BT exit pupils for my taste.  I think they make a "light" UHC as well, though, but I haven't tried those. 

 

Rich



#25 Fiske

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Posted 13 July 2021 - 09:23 PM

Thanks, Rich. That seems like a good approach. I would really only do it with long focal length EPs to maximize brightness.

 

Fiske




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