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Swarovski BTX for astro use ?

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#1 Pinac

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Posted 27 July 2018 - 04:28 PM

Serious astronomers will always sneer at people using spotting scopes for astronomy. Way too many lenses, too much glass, with transmission figures in the high 80%s, instead of 90% and more as in proper astro refractors, therefore too much loss of light and contrast, and on top of that, spotting scopes usually come with a zoom eyepiece which is known to be sub-optimal optically when compared to a fixed focus eyepiece.

 

Nevertheless ....

 

Assuming you are a birder who got a Swarovski BTX and wonder whether you could use this to occasionally venture a bit into night sky observations ...

The BTX has received acclaim and excellent reviews for birding, wildlife and nature observation, see e.g.

http://www.houseofou...tember-2017.pdf

 

The BTX is a Swarovski ATX spotting scope with, instead of the regular ATX zoom eyepiece, a BTX binoviewer attached. The largest model is based on the 95mm objective module. With the ATX zoom eyepiece, you get a 30-70 x 95 spotting scope. If you attach the BTX eyepiece, you get a 95mm spotting scope with a 45 degree binoviewer and 35x magnification. With the optional ME 1.7x Extender, you get a spotting scope with 45 degree binoviewer and 60x magnification.

With the modular design of the Swarovski scope, you can therefore switch between the following configurations:

• 95mm (= 3.75‘‘) ATX spotting scope with 30x-70x magnification
• 95mm ATX spotting scope with 50x-120x magnification, using the 1.7x extender
• 95mm BTX spotting scope with binoviewer and fixed 35x magnification
• 95mm BTX spotting scope with binoviewer and fixed 60x magnification, using the 1.7x extender

 

Not with one word does Swarovski mention a potential usage of the ATX / BTX for astro on  their website. It is only promoted for birding and nature observation. Nevertheless ....

 

I have been taking advantage of the nice weather the last few week to try out the BTX under the night sky. Seeing conditions at my location were average for deep sky but very satisfactory for the Moon, Jupiter and Saturn, so I focused on those three.

Some time ago, I had briefly used the BTX at 35x on the moon and found that it almost matched the optical performance of the Highlander 32x82 - not in terms of brightness, but contrast, detail recognition, absence of CA, edge sharpness were outstanding in my eyes.

 

This time, I used the BTX with the extender providing 60x, and intermittently, I switched to the ATX eyepiece (still with the extender) for some „high mag“ views at 100x and beyond.

To compare the Swaro, I used it side by side with both APM 70 ED and APM 82 ED BTs, the 70 with the Vixen SSW 7mm eyepiece (providing 57x magnification), and the 82 with the DeLite 7mm (providing 67x). With the BTX at 60x, I thought that would allow some sensible comparisons.

 

The BTX is almost the same length as the APM 82, but this one weighs – without eyepieces - 9.9 pounds, the APM 70 weighs 8.3 pounds. The BTX including extender and everything weighs 6.6 pounds, which makes its handling easy and the demand on mount and tripod modest.
I used the Vixen and Omegon fork mounts for the APM 70 and 82, respectively; Swarovski offers aluminium and carbon tripods of its own, and I used the heavier (but cheaper) aluminium tripod. Swarovski also offers its own mount which, together with an optional mount plate which allows the balancing out of the BTX, allows for a very smooth operation.

 

Moon (observed over a number of days)
The immediate impression: The BTX is slightly less bright than the 82 and the 70. This is not because of the size of the exit pupil (it’s 1.6mm in the BTX, and it was 1.2mm in each of the two APMs), but due to the “binoviewer effect”: with only one tube and a split light beam, there is less light for each eye.
The field of view is slightly smaller than in the 70 and roughly comparable with the 82, in the BTX the full moon disk and a surrounding circle of dark sky are visible. Edge sharpness is excellent in the BTX and at least on par with or better than the one in the APMs (for which I had chosen very good eyepieces, I believe). CA is well controlled, there is just a tiny hint of it in the outer parts of the FOV.
Central sharpness is also excellent. Rupes recta was no challenge for either instrument, Rima Birt, however, was beyond any of them.
(( Remark: switching to the one-eyed ATX configuration and using higher magnifications at 100x up, Rima Birt could just be detected ))
Rima Hyginus was again well visible in both the BTX and APM 70, but for some reason barely visible in the APM 82.
Vallis Schroeteri (best visible 3 nights before full moon) was again very well visible and clear with lots of detail in the BTX, followed in image quality by the APM 70 and then the APM 82.

Overall, as mentioned, the view in the BTX is slightly less bright in the BTX, which could explain why I was seeing so much detail on the surface of the moon (less dazzling than in the APMs), which could also mean that the BTX might be less ideal for deep sky observations, where light is usually a “scarce resource”. For the “moon hopper”, however, the BTX – both at 35x and at 60x – seems to be an excellent companion at this range of magnifications.

 

Jupiter (observed on three consecutive days)
Same immediate impression as on the moon: the image of the BTX is just slightly less bright than in the APMs. And same impression regarding central sharpness, contrast and absence of CA. Several horizontal bands are easily visible on the planet surface, the main ones – NEB and SEB – quite prominent. The BTX even shows the swirly nature of SEB quite nicely, I have hardly seen it that clearly in this instrument size.
The image in the two APMs is generally similar, but I recognized the swirls in SEB only after having seen them so clearly with the BTX and having specifically looked for them.
The large moons are obviously well visible, they are very point-like in the BTX and the APM 70, a bit “fluffier” in the APM 82.

 

Saturn (observed on two consecutive days)
Similar impression as with Jupiter, the BTX fares very well. I tried to see the Cassini division, but this was more guesswork than anything else in all three instruments, so I would say it was a “not visible”.
((Remark: just to confirm, I switched over to the ATX configuration and went up to 90-100x, then the division became visible))
It seemed to me that I could see the slightly brighter or “whiter” zone around the equator of the planet body, with the northern and southern parts of the planet darker than the central part. It was best visible in the BTX, which provided again very good contrast, and almost as well with the APM 70, a bit less so with the 82.

 

Preliminary conclusion:
The BTX competes rather well with similar sized binoscopes on objects like the moon and large planets. Whether its slightly darker image would represent a bit of a handicap for deep sky observations would remain to be seen (I would suspect it), but maybe large bright objects such as M42 would be manageable with it.

Is this a recommendation to buy a BTX for astro usage ? No. The only thing I wanted to find out was whether the avid birder with his or her BTX could also use it with profit for an occasional evening under the sky, instead of buying additional gear. In my opinion, the BTX performs well under the circumstances described above, plus it’s easy to handle and very light weight.

The keen astronomer, however, will probably be better off buying dedicated astro equipment, such as a binocular telescope, not least because of the price (the BTX with the mentioned accessories costs about as much as a same size Binoptic cost at the time, and roughly twice as much as e.g. an APM 82 with 2 sets of very nice eyepieces), but also because of the higher flexibility of a BT (the BTX can only be used with 35x and 60x).

 

For what it’s worth.
Pinac

 

The image below:
The APM 82 ED and the Swarovski BTX side by side

Attached Thumbnails

  • IMG_0704.JPG

Edited by Pinac, 27 July 2018 - 04:31 PM.

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#2 Tamiji Homma

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Posted 27 July 2018 - 05:12 PM

Thanks, Pinac for the review.

 

I sometimes walk up to hill (1.5 miles 300 feet climb) to observe.

 

I couldn't carry Kowa Highlander with me there.  It is too much.

 

I take spotting scope (Kowa Prominar with 1.6x extender) on photo tripod  with me when I need power (up to 100x-ish).

None of my astro refractors that I can carry up to the hill beats Kowa Prominar :)

 

I thought about BTX since I have a leftover ATX 95 with 1.7x extender around from ATX 95 binoscope project.

It is nice to be able to use both eyes... :)

 

Probably next year...

 

Tammy


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#3 Pinac

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Posted 28 July 2018 - 12:55 AM

Tammy,

looking at the quality of the Swaro optics, the ATX in binoscope configuration (2 tubes) must be a an absolute killer! Fabulous contrast / sharpness AND brightness, I guess.

 

Pinac


Edited by Pinac, 28 July 2018 - 01:02 AM.


#4 edwincjones

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Posted 28 July 2018 - 01:13 AM

SW BTX for astronomy?

I think you answered the question well.
It has been said many times that all optics are compromises
and you have reported that once again.

thank you,
edj
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#5 Mad Matt

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Posted 28 July 2018 - 02:26 AM

Thanks for the awesome review Pinac. I had the chance to do some daytime observations with one at the ITV this year. My impressions where the same as yours.

I would only add a comment that when you look through them, the view (einblickverhalten) „felt“ just like my EL 8.5x42. It thought that was nice 😁
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#6 teelgul

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Posted 28 July 2018 - 02:44 PM

 A Great topic and very nice review ! I have looking up  for such a comparison. For astro / birders BTX gives the best of both.

Cheers

Vaidya


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#7 JMKarian

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Posted 28 July 2018 - 08:08 PM

Pinac

I have used my BTX/95 (no 1.7 extender) for about 2 weeks, and am extremely pleased with it’s performance both from a terrestrial and its - as expected - limited  celestial capacity.  As mentioned - compromise is the “coin of the realm” within the optical world - a reality based on physics, practicality and economics. IMHO,  I would guess that the BTX/95 Swaro  — used for Astro — would best most Astro scopes used for terrestrial usage on a “grab and go” basis.  Even comes with a finder - and a forehead rest!

 

 

Clear Skies

John


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#8 Pinac

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Posted 29 July 2018 - 12:52 AM

John,

 

I agree with you. But question: how do you use the finder at night?

It works fine during the day, but I can‘t see the reticule when it‘s dark, so I mounted a red dot finder for night use.

 

Pinac



#9 Stellarfire

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Posted 29 July 2018 - 01:21 AM

looking at the quality of the Swaro optics, the ATX in binoscope configuration (2 tubes) must be a an absolute killer! 

 

Tammy did it, see his CN-report Swarovski ATX 95 binoculars with Matsumoto-san's EMS. like-button.jpg

 

Picture  (post #32)

 

Picture  (w/ Docter UWA 12.5, post #51)

 

Picture  (besides Kowa Highlander, post #58)

 

 

Esteban


Edited by Stellarfire, 29 July 2018 - 01:40 AM.


#10 Pinac

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Posted 29 July 2018 - 04:11 AM

Thank you, Esteban / Stefan.
I had actually been looking for that, but had not immediately found it mad.gif

 

Tammy, have you ever reported in some detail on the performance of your very special setup, or are you planning to do that ?

 

Pinac



#11 JMKarian

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Posted 29 July 2018 - 06:09 AM

Pinac,

The Finder, by itself,  is not helpful for me at night either.  I use a small green laser penlight held parallel to the finder - this gives a crude approximation to night localizations

 

By the way, I enjoy the BTX/95 most when I am seated  at eye level within 5-6 meters of a perennial flower garden.  It truly gives you a butterfly’s / hummingbirds eye of activity.  Yes, I do a fair amount of re- focusing from flower to flower, but the Swaro’s optics scream with sharp detail and vivid color saturation, especially when contrasted with a dark, out-of-focus background.  “Eye-Candy” at its finest!  I use the Swarovski professional tripod head with balance rail atop a robust Gitzo carbon fiber tripod.  The Swaro’s tripod gimbal Type head is well-built, and works well at most declinations - except at zenith. 

 

I have also constructed a small table top tripod head mount for use when I’m seated at a picnic table.

 

John


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#12 Tamiji Homma

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Posted 30 July 2018 - 02:14 PM

Hi Pinac,

 

 

Tammy, have you ever reported in some detail on the performance of your very special setup, or are you planning to do that ?

 

The ATX95 binoscope project to view Horsehead from my backyard with less than 4" aperture.

The setup was light enough to carry as a whole, stepping out to backyard.

 

https://www.cloudyni...-2#entry5775622

 

After that, I often used the setup for (bright) comet.  It really shines with a pair of Docter UWA 12.5s.

 

I am now working on lighter setup (two trips instead of five trips) for TEC 140ED binoscope for more observing.

 

Tammy


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#13 Crusty99

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Posted 30 July 2018 - 11:37 PM

Very nice report.

 

Birdwatching with a binoviewer on a small refractor (70mm, 80mm) is something I have been doing for several years now.

 

I also switched to binoviewing planets and bright objects in the night sky.

 

You can also mount a small refractor with binoviewer on a stable parallelogram.

 

Very enjoyable. 

 

Congratulations on your set up. 


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#14 DRodrigues

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Posted 05 August 2018 - 09:40 AM

Thanks for the review Pinac. waytogo.gif

 

You can add a second 1.7x extender and get 101x with the BTX, and you can continue to add 1.7x extenders...wink.gif

 

Regarding the use of the X95 lens module for astro viewing you can get some ideas at http://www.pt-ducks....i_X_derivations but I discovered that the X lens modules need the correction of the ocular module for best results. However I found there are other good quality solutions - I found a low cost straight prism that allows the use of 2" eps with good results - will inform when update the page...


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#15 hk112

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Posted 15 August 2018 - 01:20 AM

Thanks for this great review Pinac.flowerred.gif

 

bawling.gif You made me want to sell my kowa 883 to get the awesome BTX set,

only if  I could save enough money to fill the gap between them.



#16 Pinac

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Posted 15 August 2018 - 11:17 AM

Hmm ... are you sure, hk112?

I don‘t know the  Kowa 883, but everyone who has one seems thrilled about it‘s performance, so I would think twice before getting rid of it. Of course, it‘s a single eye scope, but could you fit a binoviewer?



#17 hk112

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Posted 15 August 2018 - 08:30 PM

Hi Pinac. IMHO Kowa 883/884 has the best CA correction among the spotting scopes, resolution is also top notch. 

But I'm spoiled by the comfort of binos already, unfortunately the kowa can not accept a binoviewer, due to limited back foucus, at least to get infinite focus is impossible.

I think BTX is a good combination of portability and comfort (use with two eyes).

flowerred.gif Thanks for your advice Pinac, I will think twice before pulling the trigger. 

I've heard that a local friend just bought a BTX 95, perhaps I should visit him to see the scope in reality first.

 

 

HK


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#18 DRodrigues

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Posted 19 August 2018 - 02:13 PM

..., unfortunately the kowa can not accept a binoviewer, due to limited back foucus, at least to get infinite focus is impossible.

I think BTX is a good combination of portability and comfort (use with two eyes).

...

You can use a binoviewer with the Kowa scope if is one of the type of https://www.teleskop...rect-image.html. However resulting images will be inverted in all directions. You could solve the "problem" using the Kowa adapter for DSL photo but magnifications would increase (although having a zoom...), resulting cost would be lower than the BTX but would be much longer and most probably the image quality would be no way near than that of a BTX...



#19 hk112

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Posted 19 August 2018 - 08:54 PM

Thanks david.flowerred.gif

I mainly use the spotting scope for birding, so perhaps a reversed image or too much magnification is not very suitable.

But thank you all the same.

Last weekend I have visited a local BTX scope owner, one of my friends.

After 2 hours watching birds through the BTX, and a comparison against my kowa 883 side by side, I still couldn't make a decision to jump to the BTX.

Of course BTX was much comfort to use, and seemed a little more crystal. The 883 has better CA correction, and brighter at same magnification.

Also the swaro costs almost twice as kowa.

undecided.gif ...inner peace, inner peace...


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#20 edwincjones

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Posted 20 August 2018 - 04:54 AM

Thanks for this great review Pinac.flowerred.gif

 

bawling.gif You made me want to sell my kowa 883 to get the awesome BTX set,

only if  I could save enough money to fill the gap between them.

I chose the 883 instead of the BTX - two eyed viewing would have been nice/great,

but did not feel the double cost was worth it as good as the 883 is.

I will probably always wish, but do not regret.

Just a law in optics-a lot of money for a little improvement!

 

the other negative with the BTX is one cannot use it with  zoom-it is one eyed zoom or two eyed fixed mag

 

edj


Edited by edwincjones, 20 August 2018 - 04:57 AM.

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#21 Erik Bakker

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Posted 20 August 2018 - 06:47 AM

While good, I don't find my experience with the BTX as good as with a top quality binoviewer and ditto eyepieces. On the plus side, it's waterproof. But a lot more bulky than the mono Kowa 883 or Swaro spotting scopes for that matter.



#22 edwincjones

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Posted 20 August 2018 - 09:28 AM

It is really pretty simple

-Spotting scopes are made for birders

-Telescopes are made for astronomers

-Binoculars are made for handheld, two eyed observing

Just gets complicated when we start mixing functions

 

edj


Edited by edwincjones, 20 August 2018 - 09:29 AM.

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#23 Blue72

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Posted 20 August 2018 - 10:32 AM

It is really pretty simple

-Spotting scopes are made for birders

-Telescopes are made for astronomers

-Binoculars are made for handheld, two eyed observing

Just gets complicated when we start mixing functions

 

edj

The more I try to mix functionality the more I realize you need the proper tool for the task at hand.

 

thats coming from a guy who loves his spotting scope for astronomy 


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#24 Mad Matt

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Posted 20 August 2018 - 11:21 PM

It is really pretty simple
-Spotting scopes are made for birders
-Telescopes are made for astronomers
-Binoculars are made for handheld, two eyed observing
Just gets complicated when we start mixing functions

edj


It does not get complicated... it simply gets expensive! flowerred.gif grin.gif smile.gif


Edited by Mad Matt, 21 August 2018 - 04:40 AM.

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#25 edwincjones

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Posted 21 August 2018 - 05:01 AM

that also  bigshock.gif




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