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Kowa announces 1.6x extender for small body scopes! (1 Viewer)

Hi,

yes together with the 30 wide this would give sth around 45x wide angle. Or higher to mag with the zoom.

Joachim
 
I use the following older Kowa eyepieces with my older Kowa TSN-661 (non-ED) scope.

TSE-21WD (20X, 3.3 exit pupil, 3.3° FOV)
TSE-14WD (30X, 2.2 exit pupil, 2.4° FOV)
TSE-9WD (45X, 1.5 exit pupil, 1.5° FOV)

I carry the three eyepieces around in a separate camera bag, along with a polarizing filter to reduce glare on water views.

Of the three Kowa eyepieces, I mostly use the 20X and 30X. Between those two eyepieces, I use the TSE-21WD (20X) the most due to the brighter views and wider FOV.

When I want more power, I usually go with the TSE-14WD (30X).

I use the TSE-9WD (45X) for closeup views (30 yards or less) of birds and flora on bright sunny days. When I originally purchased the 45X I thought I would use the eyepiece for distant views. But it just has not worked out that way for me.

Crusty
 
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Crusty said:
I use the TSE-9WD (45X) for closeup views (30 yards or less) of birds and flora on bright sunny days. When I originally purchased the 45X I thought I would use the eyepiece for distant views. But it just has not worked out that way for me.

Crusty
Click to expand...

Crusty
Is this because of the image degradation caused by heat shimmer over longer distances?

Lee
 
Crusty said:
I use the following older Kowa eyepieces with my older Kowa TSN-661 (non-ED) scope.

TSE-21WD (20X, 3.3 exit pupil, 3.3° FOV)
TSE-14WD (30X, 2.2 exit pupil, 2.4° FOV)
TSE-9WD (45X, 1.5 exit pupil, 1.5° FOV)

Crusty
Click to expand...

One wonders if Kowa has any plans to upgrade/replace the TE-9Z eyepiece ... perhaps with something more on the lines of the TE-11WZ.

Granted a lot of this is just personal preference, but I originally bought a TSN-601 scope with the TS-9Z and found that 20-60 zoom rather unappealing. I quickly purchased the TE-14WD and found the 30X eyepiece much more comfortable to use. (I'm in the middle of a coast-to-coast move and I packed away the TE-9Z in the household goods. Don't miss it a bit.)

I just upgraded to a TSN-663M -- where the TE-14WD continues to prove itself a comfortable eyepiece. Kowa seems to be consolidating their product line (reducing SKUs), and it would be a shame if they cut that eyepiece.
 
Troubador said:
Crusty
Is this because of the image degradation caused by heat shimmer over longer distances?

Lee
Click to expand...

The heat shimmers during mid-day do cause image degradation with the 45X eyepiece. That is a major reason I drop down and use the 20X or 30X.

Other major factors limiting my choice of the 45X for distance viewing are brightness and FOV.

I have several refractor astronomy scopes, but none of them beat my old Kowa TSN-661 for convenience in the field.

Crusty
 
ljclark said:
Granted a lot of this is just personal preference, but I originally bought a TSN-601 scope with the TS-9Z and found that 20-60 zoom rather unappealing. I quickly purchased the TE-14WD and found the 30X eyepiece much more comfortable to use. (I'm in the middle of a coast-to-coast move and I packed away the TE-9Z in the household goods. Don't miss it a bit.)
Click to expand...

I also started out with the TS-9Z zoom, but returned it and decided to go the single eyepiece route because I wanted a larger exit pupil and FOV.

I envy your upgrade to the ED model. Several times I have wanted to do the same thing -- but always spent the money on other optics. I guess upgrading is still an option.

Here is a nice video of the TSN-663 on YouTube.

Crusty
 
Hi,

in my experience my TSN-3 is most often used at the maximum magnification possible with the SDLv2 zoom on it - 52x. I use bins for survey and a cable tie sight for aiming and rarely zoom out to lower mag, usually when it's getting really dark.

Although over here in germany heat shimmer does not happen so often and my day patch is looking at the nature reserve over the river from the balcony, which probably helps...

I sometimes use astro scopes at much higher mag from the balcony terrestially without problems.

Really looking forward to the extender... although I would have to check if it'll work with the Opticron EP - bringing my 30 wide to 45 wide is not so interesting as the zoom is nice and wide at the high mag end too...

Joachim
 
Here is a link (with video) from Kowa USA about the Kowa 1.6x extender for small body scopes. Also includes a compatibility chart on the webpage. The video shows other System S products for Kowa scopes.

Questions

Q1 The advertising copy says the 1.6X extender will result in "virtually no light loss". Does this mean the exit pupil size for fixed Kowa eyepieces will remain the same?

Q2 Will the 1.6X extender affect FOV for use with fixed eyepieces?
 
Crusty said:
Questions

Q1 The advertising copy says the 1.6X extender will result in "virtually no light loss". Does this mean the exit pupil size for fixed Kowa eyepieces will remain the same?

Q2 Will the 1.6X extender affect FOV for use with fixed eyepieces?
Click to expand...

Hi,

regarding your first question - I guess it refers to the extender not having many groups and thus surfaces plus current multicoatings which will result in a transmission loss below 1%, maybe even below 0.5.

Simple physics dictates that the exit pupil must be 1.6 times smaller with the extender than without.

Exit pupil = objective aperture / magnification

True field of view will be reduced by the factor of 1.6 when magnification rises accordingly, the eyepiece apparent field of view will remain unchanged.

Joachim
 
Joachim...

Thank you for your comments to my two questions about the Kowa 1.6X extender.

Looks like the benefits of the Kowa 1.6 extender are magnification increase at the cost of exit pupil and true field of view.
 
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Thanks to Joachim, I am posting the effects of adding the new Kowa 1.6 Extender to the Kowa 660 scopes.

I use the Kowa fixed eyepieces for the Kowa 660 series.
First line -- eyepiece model.
Second line is the fixed eyepiece result on a 660 scope without the new 1.6X extender.
Third line is the result of adding the new Kowa 1.6X extender.

TSE-21WD
20X, 3.3 exit pupil, 3.3° FOV (without 1.6X extender)
32X, 2.0 exit pupil, 2.0° FOV (with 1.6X extender)

TSE-14WD
30X, 2.2 exit pupil, 2.4° FOV (without 1.6X extender)
48X, 1.4 exit pupil, 1.5° FOV (with 1.6X extender)

TSE-9WD
45X, 1.5 exit pupil, 1.5° FOV (without 1.6X extender)
72X, 0.9 exit pupil, 0.9° FOV (with 1.6X extender)

Is the 1.6X Extender something I should purchase for my Kowa 660 series optical system?
 
jring said:
Hi,

regarding your first question - I guess it refers to the extender not having many groups and thus surfaces plus current multicoatings which will result in a transmission loss below 1%, maybe even below 0.5.

Joachim
Click to expand...

All my experience with converters is using them with still photography cameras, so...

Isn't this 1.6x extender essentially the same as a photographic teleconverter? If so, shouldn't I be expecting a light loss of more than one f-stop?
 
Hi,

@Crusty - I really don't know if the extender makes sense for you since you have the rare 45x wide along with the other two. The only really new magnification would be 72x which might or might not be useful to you. With a 66mm objective this yields an exit pupil of less than 1mm which means it can only be used in good light and eye placement is critical. Also it will certainly not be useful with a non-ed body like the (661/2) - the image will most probably be blurry due to longitudinal CA.

@ljclark - the smaller exit pupil is the reason for the light loss. To put it in f stops - the 660 series scopes have 420mm focal length / 66mm aperture giving f6.4. With the extender the effective focal length goes up to 672mm and focal ratio is then f10.2 - that's your more than an f-stop.

Joachim
 
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I will say that the 20-60 eyepiece works better on the 660 series than the 600 scopes. My own feeling is that the extenders should be left to the big boys the 77 and 88 scopes The 1.6 on my 884 causes a slight light loss but very slight and the view all they out is amazing if its a clear calm day.
Steve
 
Stephen Mark said:
I will say that the 20-60 eyepiece works better on the 660 series than the 600 scopes. My own feeling is that the extenders should be left to the big boys the 77 and 88 scopes The 1.6 on my 884 causes a slight light loss but very slight and the view all they out is amazing if its a clear calm day.
Steve
Click to expand...

I would expect that you'd end up with less than half the light by using the 1.6x extender.
 
ljclark said:
I would expect that you'd end up with less than half the light by using the 1.6x extender.
Click to expand...

That might be true if this was a photo camera with a fixed image area... but if you look though your scope visually, it really depends on the conditions. In bright daylight your eyes pupil is quite small and any exit pupil larger than that is wasted.

In my experience exit pupils of around 1mm work fine visually in good light, at dusk you want to turn down the magnification.
At night while stargazing you can go quite a bit higher for some objects - 0.5mm exit pupil is often said to be the limit of useful magnification and as often is proven wrong by people using even higher magnifications.

Joachim
 
The TSN-663M XD Prominar arrived this week and I made a quick comparison with my older TSN-661.

The 663 delivers better nature views than my older 661 with all three of the Kowa fixed eyepieces. And I noticed a major improvement with the TSE-9WD 45X in the 663.

My two observing objects:

  • Large Red Maple tree at 165 yards -- leaves against the bright sky and shaded bark texture.
  • Robin on the front lawn at 10 yards.
I am very pleased with the my Kowa 660 optical system -- two scopes, 3 fixed eyepieces, 3 filters for objective lens.

The TSE-9WD 45X fixed eyepiece delivers nice views with the 663M -- giving me a 1.5mm exit pupil and 1.5° FOV.

*****

Joachim, I had no idea the 45X is such a rare eyepiece. I do remember when I purchased it a few years back -- the eyepiece only seemed to be on the market for a short period of time. I think I got the last one my dealer had in stock.

*****

I probably will follow the advice in this thread -- NOT ADDING the 1.6X extender for my 660 system at this time -- because of loss of light and FOV results.

I have found great benefits come from the following.
  1. learn an optical system
  2. stay with the system
  3. use the system
And finally, I do think Kowa should bring back the three fixed eyepieces for the 660 series since the 20-60 zoom is just so-so -- light and FOV are important to visual users of the 660 scopes.
 
Crusty said:
And finally, I do think Kowa should bring back the three fixed eyepieces for the 660 series since the 20-60 zoom is just so-so -- light and FOV are important to visual users of the 660 scopes.
Click to expand...

An alternate approach would be for Kowa to remount the 25-60X Wide zoom eyepiece (which has ED elements) for the System S scopes.

As I've said before, it seems like Kowa is cutting back on SKUs. I hope they don't cut the TE-14WD. If they did, we should gather up our torches and pitchforks and surround Kowa headquarters. :storm:
 
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