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Televue 85mm Refractor or Kowa TSN880?

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#1 Brian57

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Posted 20 October 2021 - 02:06 AM

Are the Kowa 880 and the new 990 spotting scopes suitable for astronomical use? They have fluorite objective lenses--and the 990 is listed as a doublet with a concave element. (Not sure if the 880 has the same.) Anyway, my question is this: Are these Kowa scopes as suitable for astronomical viewing as, say, a Televue 85mm refractor? FWIW, I already have a selection of decent 1.25 eye pieces I use with my Pentax PF80 that would carry over to the Televue; would either of the Kowas or a Televue be a worthy upgrade? If so, any thoughts on which? Many thanks.


Edited by Brian57, 20 October 2021 - 02:10 AM.


#2 db2005

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Posted 20 October 2021 - 04:54 AM

It stands to reason that it's a good idea to use whatever scope one already owns to gaze at the stars, whether it be a spotting scope or a dedicated astronomical telescope. Having any telescope is better than having no telescope.

 

However, if you are in the market for a new scope and want the best performance for astronomical use and the compactness of a spotting scope isn't important to you, a dedicated astronomical telescope like the TV-85 or one of many fine alternatives will most likely be a much, much better choice. The main reason is that spotting scopes are designed with daytime use in mind which involves some real performance-wise tradeoffs: erecting prisms cause degradation of images which is noticeable when observing stars at high medium to high magnifications; fast focal ratios mean that color correction and other aberrations cannot be as well controlled, meaning that maximum useful magnification will be fairly limited compared with a dedicated astronomical telescope; and extra optical elements cause loss of light and contrast compared with a TV-85. Then there's the observing position of the spotting scope which will be uncomfortable at higher elevations. With a dedicated telescope you just use a right-angle star diagonal. The main appeal of a daytime spotter is daytime use: low weight, portability and incredible compactness.

 

The TV-85 and the Kowa scope are fairly expensive pieces of gear. There are many excellent alternatives; FWIW I wouldn't underestimate the usefulness of a quality slow 80 mm-class achromatic refractor on a sturdy alt-az mount. A complete setup like that can be had at a fraction of the price.


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#3 gzljh96

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Posted 20 October 2021 - 05:15 AM

A dedicated astronomical telescope will be better for viewing stars for a few reasons.

But the TV-85 is a very expensive piece of gear. It’s not a bad choice, but you have a lot of choices around that price point.
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#4 Jon Isaacs

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Posted 20 October 2021 - 05:56 AM

Are the Kowa 880 and the new 990 spotting scopes suitable for astronomical use? They have fluorite objective lenses--and the 990 is listed as a doublet with a concave element. (Not sure if the 880 has the same.) Anyway, my question is this: Are these Kowa scopes as suitable for astronomical viewing as, say, a Televue 85mm refractor? FWIW, I already have a selection of decent 1.25 eye pieces I use with my Pentax PF80 that would carry over to the Televue; would either of the Kowas or a Televue be a worthy upgrade? If so, any thoughts on which? Many thanks.

 

Brian:

 

For astronomy, an standard astronomical refractor with a 90 degree diagonal is much better ergonomically than a spotting scope.  A spotting scope, even with a 45 degree focuser is just awkward and uncomfortable for viewing most of the sky.  The simpler optical path of the astro-refractor with a 90 degree star diagonal is less compromised at high magnifications and the 2 inch focuser can provide a field of view as wide as 4.4 degrees in the TV-85.  Those low power, wide field views are something 80mm refractors excel at. 

 

The Kowa, if it takes standard 1.25 inch eyepieces, is an upgrade to your PF-80 but is basically the same thing, same issues.  A TeleVue 85 or other small astro apo would be a more comfortable, more capable scope for astronomy.

 

Jon 


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#5 alnitak22

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Posted 20 October 2021 - 07:13 AM

Are the Kowa 880 and the new 990 spotting scopes suitable for astronomical use? They have fluorite objective lenses--and the 990 is listed as a doublet with a concave element. (Not sure if the 880 has the same.) Anyway, my question is this: Are these Kowa scopes as suitable for astronomical viewing as, say, a Televue 85mm refractor? FWIW, I already have a selection of decent 1.25 eye pieces I use with my Pentax PF80 that would carry over to the Televue; would either of the Kowas or a Televue be a worthy upgrade? If so, any thoughts on which? Many thanks.

Brian,

 

I’ve had a TeleVue 85 since 2000 and it’s a great choice for both astronomy and nature observing.  For astronomy, it’s ability to use premium 2” eyepieces like the 22 T4 Nagler is a big plus. The best way to look at it is the TV85 crosses over to a spotting scope role much better than the Kowa crosses over to astronomy. 


Edited by alnitak22, 20 October 2021 - 07:28 AM.

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#6 Brian57

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Posted 20 October 2021 - 11:56 PM

Thanks to all of you who took the time to reply--with many things I hadn't considered or just didn't know. I'll start focusing on Televue or a similar sized refractor and set the prospect of getting a bigger Kowa aside--especially since I already have my share of terrestrial spotting scopes.

 

Appreciated,

 

Brian


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#7 TomK1

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Posted 21 October 2021 - 12:44 AM

No.

 

Buy a refractor with a right angle diagonal if you want to view seriously at night.  The refractor is vastly more versatile: brighter image, wider fov, double the magnification,  ergonomically vastly superior for astronomy.  How do feel after 2 hrs of constant viewing at night, scanning all areas of the sky concentrating on the objects overhead with your Pentax PF80?   

 

Sell your Pentax and buy the Kowa if you're angling for a heavier and more optically superior spotting scope for terrestrial viewing.  But wow, the Kowa 990 is around $4000.   That would buy a wonderful astronomical set-up.

 

My 30-60w Meopta 82mm ED spotting scope set up is wonderful for terrestrial  viewing and is abysmal for astronomy.  

 

I just noticed your collection.  I think you're looking for an excuse to add to your collection.  The 990 would be a next bump up.   If you have the $, go for it.  And then also buy an astronomical refractor.


Edited by TomK1, 21 October 2021 - 12:45 AM.

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#8 gzljh96

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Posted 21 October 2021 - 05:07 AM

Thanks to all of you who took the time to reply--with many things I hadn't considered or just didn't know. I'll start focusing on Televue or a similar sized refractor and set the prospect of getting a bigger Kowa aside--especially since I already have my share of terrestrial spotting scopes.

Appreciated,

Brian


Don’t limit yourself to Televue. The TV-76 and 85 are terrific scopes, but some other makers, like Takahashi from Japan or APM from Germany also make fantastic telescopes. If you want made in USA you can go for Astro-physics and Stellarvue, both of which have a good reputation here, but you might be on the waitlist for a long time. Or you can also go cheap and get Chinese-made scopes like the Skywatcher 80ED, which apparently also has pretty good optics, albeit not as good as Takahashi and Televue.

#9 Mark9473

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Posted 21 October 2021 - 05:34 AM

What I read on BirdForum is that the new Kowa 990 does not live up to the well-established optical quality of the 880.

#10 Brian57

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Posted 22 October 2021 - 12:58 AM

Don’t limit yourself to Televue. The TV-76 and 85 are terrific scopes, but some other makers, like Takahashi from Japan or APM from Germany also make fantastic telescopes. If you want made in USA you can go for Astro-physics and Stellarvue, both of which have a good reputation here, but you might be on the waitlist for a long time. Or you can also go cheap and get Chinese-made scopes like the Skywatcher 80ED, which apparently also has pretty good optics, albeit not as good as Takahashi and Televue.

Thanks GZ. I'll look at all these before I leap!




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