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Kowa Evaluation Period (1 Viewer)

I bought an 883 scope with the 25-60 eyepiece and the 1.6 extender. I have no other scope or reference compare this scope to. I am wearing progressive glasses which I have never quite become fully comfortable with when looking through binoculars or scopes. I normally remove them for thsi purpose. This Kowa scope seems very good with nice colors and contrast. There are wow! images at certain distances. Seagulls can be very intersting with a scope. With the extender the image is softer at the far end of the zoom. With the extender off, the image is also softer at 60x. If I put my glasses on, it is harder to get the full field of view against the eyepiece, but I might be able to achieve a sharper focus. I can't be sure. I bought the PhoneSkope digiphone adapter and I'm still working with it. I'm undecided about it.
I wonder if a different sample of the scope or extender will change anything. And I wonder how to view with glasses/without glasses. Any suggestions or advice would be helpful.
 

Richard Scott

Well-known member
I bought an 883 scope with the 25-60 eyepiece and the 1.6 extender. I have no other scope or reference compare this scope to. I am wearing progressive glasses which I have never quite become fully comfortable with when looking through binoculars or scopes. I normally remove them for thsi purpose. This Kowa scope seems very good with nice colors and contrast. There are wow! images at certain distances. Seagulls can be very intersting with a scope. With the extender the image is softer at the far end of the zoom. With the extender off, the image is also softer at 60x. If I put my glasses on, it is harder to get the full field of view against the eyepiece, but I might be able to achieve a sharper focus. I can't be sure. I bought the PhoneSkope digiphone adapter and I'm still working with it. I'm undecided about it.
I wonder if a different sample of the scope or extender will change anything. And I wonder how to view with glasses/without glasses. Any suggestions or advice would be helpful.
I wear progressive glasses except when I’m birding. I much prefer using single vision lenses with bins and scope. Atmospheric conditions can badly affect the image at high magnification over long distances. I’ve got the same kit as you and one day it can be fantastic but the next day it can be shocking.
 
I'll have to go out early at first light and have a look when the atmosphere is generally more settled. Even by 0900 the heat is shimmering when the air temp is in the upper 50s. I think in general I am expecting too much as I look out too far. That said I can't get the same level of razor sharp focus out of the extender as without the extender whether I am in nearer or further. Maybe someday I'll get a range finder to get an idea of what distances make for the best viewing (and digiscoping).
I'll have to try some single vision lens glasses, although the part I look through is single vision. I'll have to sit down and really think about it. For now I'm just excited to see everything so I'm not too methodical.

I bought a Manfrotto fluid head that is decent, and a big tripod from Innorel with a 75mm bowl. This feature is really great. I can put the tripod up anywhere and simply use the bowl adjustment to quickly level the head. Also, with this tripod I can open only three of the four sections and the height is right with the angled scope for my 70" height.
 

BoldenEagle

Well-known member
Hi Jorukfundan,

If you would like to know how good sample you are dealing with, I would suggest you could do a star test or/and resolution test with your scope. There's lot of information on the topics here in Birdforum if you will do a little search.

In general and perhaps in particularly considering Kowa Prominar 883 scopes I would strongly recommend to test the sample closely and return if proven a bad one because it would be no surprise to get below average sample. Of course that is the case among at least most of the other brands also.

Here is a demonstration how my (I would say somewhere ok - good territory) sample of 883 + extender performs on good viewing conditions at a close range.


On less bright days and at longer range views are not this good and very often heat haze will destroy the image well before reaching even 60x. But if conditions are favourable, using the extender you will see smaller details than without it, provided your scope body is not a bad sample.

Regards,

Juhani
 
Thank you for your reply.
This pica pica looks very nice through the extender. Can you say what video device you are using, and what adapter to hold it?
I searched for “resolution sheet tutorial” and such but I have to keep searching. I didn’t find the test. Same with star testing, which seems harder to perform and evaluate.
Juhani,did you find variations in the eyepiece and extender, as well as the 883 scope? That’s a lot to evaluate.
 

BoldenEagle

Well-known member
I'm using Samsung Galaxy s10 lite smartphone for my digiscoping.

The adapter is diy model made of piece of wood plate, some glue, soft smartphone cover and standard Kowa adapter ring for TE-11WZ eyepiece (https://www.kowaoptic.com/kowa-tsn-ar11wz-smartphone-digiscoping-adapter-ring?c=84). Very ugly looking but light, easy to use and works great.

I haven't tested different eyepieces for sample variations because they shouldn't exist as likely as they do with scope bodies. I do have APM 12.5mm wideangle 1.25" eyepiece which sometimes feels sharper than TE-11WZ @40x but I have no quantitative proof for that. It may have slightly better contrast which makes it look sharper in normal viewing or it is just my imagination...

Regards,

Juhani
 

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jring

Well-known member
Hi,

actually a star test is easier to perform as a resolution test needs a test chart (which you might find somewhere online if you search for USAF resolution test chart) and other scopes to compare to.

A star test done on a real star does not need any stuff and it's quite sensitive, so even small errors will be shown easily. See the images on https://www.telescope-optics.net/star_testing_telescope.htm for what it should look like, specifically the unobstructed case for the aberration free aperture - the very first set. Equal patterns of well defined, concentric circles - which you rarely get.
Clear rings on one side of focus and a fuzzy disc on the other side means spherical aberration, ellipses changing main axis when going from inside of focus to outside vs. circles means astigmatism and non-concentric rings mean coma.

Joachim
 
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I'm using Samsung Galaxy s10 lite smartphone for my digiscoping.

The adapter is diy model made of piece of wood plate, some glue, soft smartphone cover and standard Kowa adapter ring for TE-11WZ eyepiece (https://www.kowaoptic.com/kowa-tsn-ar11wz-smartphone-digiscoping-adapter-ring?c=84). Very ugly looking but light, easy to use and works great.

I haven't tested different eyepieces for sample variations because they shouldn't exist as likely as they do with scope bodies. I do have APM 12.5mm wideangle 1.25" eyepiece which sometimes feels sharper than TE-11WZ @40x but I have no quantitative proof for that. It may have slightly better contrast which makes it look sharper in normal viewing or it is just my imagination...

Regards,

Juhani
Your digiscope assembly looks good. Very good. It’s simple. I might go in that direction. The. I can choose the case I want to use.
I agree with you that the scope itself is probably the unit that has the most sample variation. But I suppose the eyepieces could have some variation as well. I don’t want to over complicate the issue though.
 
Hi,

actually a star test is easier to perform as a resolution test needs a test chart (which you might find somewhere online if you search for USAF resolution test chart) and other scopes to compare to.

A star test done on a real star does not need any stuff and it's quite sensitive, so even small errors will be shown easily. See the images on https://www.telescope-optics.net/star_testing_telescope.htm for what it should look like, specifically the unobstructed case for the aberration free aperture - the very first set. Equal patterns of well defined, concentric circles - which you rarely get.
Clear rings on one side of focus and a fuzzy disc on the other side means spherical aberration, ellipses changing main axis when going from inside of focus to outside vs. circles means astigmatism and non-concentric rings mean coma.

Joachim
Mr. Joachim,
I began reading the article at the link and I thought I might need to get a whiskey. I’m wondering if spotting scopes are like guitars....you should probably buy them in person. I don’t know how you evaluate a scope in a shop though. I could imagine having a scope that I was only happy with occasionally though, at which point it would not get used very often.
 

jring

Well-known member
Hi,

the article is a bit heavy on theory as that site is a free advanced optics textbook. But the example images of what the diffraction image of a perfect star test should look like and the diffraction patterns of the different aberrations are easy enough to understand...

Enjoy your whiskey, but only one - otherwise there's always two stars vs one :)

Joachim
 
Mr. Joachim,
Yes, only one whiskey for evaluation purposes.
The article is very interesting. Maybe the most interesting. I need to find a light source and I may need to do a daytime source like some folks have done. I can't get 40-50x per inch, although I could do the minimum 88x for 88mm of aperture. Although now that I think of it an 88mm dimension referring to the objective lens, is the aperture the same size? In any case, I looked at Polaris last night and it's not bright enough to do anything. I know this is a bird forum, however I didn't see any birds in the middle of the night. I did see the moon though. I don't know much about aberration and diffraction etc, but I do know that the image is soft at high magnification, and through the 1.6x extender. I can't seem to get a razor sharp focus, but I'm still battling with my eyes and my eyes with eyeglasses on, and figuring out phone focus.

Is fine focus correlated to sample scopes, and fine focus varies from scope to scope sample?
 

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jring

Well-known member
Hi,

aperture in regards to telescopes is usually objective aperture... so yes, that would be 88mm... and for a star test, a 1mm exit pupil (as in 88mm aperture / 88x magnification) is optimal.

You should be able to see Sirius fairly low in the south for the first few hours after sundown tonight in Carmel... or Capella fairly high in the north-west... the latter will be visible later in the night too... and is probably better if you can observe over the cool ocean - less seeing.

If you want to make an artificial source, my preferred way is a bit of aluminum foil on a glass surface and then make a very tiny hole with a pin or needle. Tape that in front of a led flashlight and observe at 30m or so. If you use that, a cool and overcast morning is best for seeing.
Or you can use steel ball (or basically any fairly small spherical object) and observe a reflection of the sun from that...

The ability to get a sharp image at higher magnifications is indeed correlated to optical quality (and thus the absence of so-called aberrations, optical flaws from manufacturing defects and/or design choices). The design choices should be the same among different examples of one scope model, but manufacturing defects do vary from example to example and with the huge success of the Kowa 880 series we have heard about a few not so great examples in here (although in my personal experience the most terrible example was a brand new ATX95 of another birder - after he had looked though my very old, but better than average Kowa TSN-3 he knew that he should talk to his dealer).

Joachim, who missed the visit to Carmel and its famous mayor when he was on a highschool exchange to Monterey High in the 80s...
 
Mr. Joachim,

I am from California, but I lived in SoCal in the 80s during the famous mayor time of Carmel. Maybe the 80s was a fine time at Monterey High, when Fort Ord was still around as a military base....Sounds like a pretty good high school exchange if you ask me. Are you in a place with a different night sky and different birds now?

I found Sirius, the brightest star in the sky, as you said. I looked at it for a long, long time. I could not capture a good image with an iphone, nor a Fuji camera, or a Canon Eos M. That was frustrating.

I did see equal patterns of well defined, concentric circles when I went clockwise from focus (turning focus ring clockwise from my viewing position, eyepiece toward objective lens). Except the last ring was thicker than the inner rings.
I had a fuzzy disc on the counterclockwise side of focus, opposite the concentric ring side. I could faintly make out some concentric rings in the fuzzy side, but only the outer rings, and very faint.
The images looked the same with or without the 1.6 extender.

What does spherical aberration mean to me with this scope? Maybe it is the reason I can not achieve the very sharpest image at higher magnification?

I don't think I saw any ellipse changing main axis when going from one side of focus to the other side, and I did not see any non-concentric rings.

Thank you for the clear description of the three things to look for- spherical aberration, astigmatism, and coma.
"Equal patterns of well defined, concentric circles - which you rarely get.
Clear rings on one side of focus and a fuzzy disc on the other side means spherical aberration, ellipses changing main axis when going from inside of focus to outside vs. circles means astigmatism and non-concentric rings mean coma."

Jordan
 

jring

Well-known member
Hi Jordan,

yes, I'm in Germany unless on vacation or the occasional business trip... both of which didn't happen a lot in the last year due to the state of the world... so the stars are not different but the birds are...
The Monterey Bay area was great back then - lots of interesting stuff to see and do... Cannery Row was a bit touristy but still nice to see what they made of the original from John Steinbeck's novella (which we had read in school before) and the aquarium was a big thing back then... and still got fond memories of some nice field trips to Point Lobos and Big Sur.

The term spherical aberration comes from reflector telescopes of the Newtonian type - there the ideal mirror form is a parabola and if you use a spherical mirror (at least for instruments faster than f10 or so), rays which are reflected from the edge of the mirror come to focus at a different point than rays reflected close to the center of the mirror.
Consequently spherical mirrors are quite a bit undercorrected and mirrors which exceed the ideal parabolic form are called overcorrected.

The same terms are used for a similar symptom in refracting telescopes too but the term spherical aberration does not make sense here - most refracting telescope are built from lenses with spherical surfaces and they still can be made to have no spherical aberration - when well designed and made to high standards.

Whether your example is over- or undercorrected remains to be seen, we need to know if the well defined rings were outside of best focus (so the instrument was set for close focus - that would be overcorrected as shown in the examples on telescope-optics.net) or inside of best focus (beyond infinity focus which results into undercorrected).

In any case if the SA ist strong enough to give soft images at high mag with the extender, you might want to return your example and try to get a better one... how are things at 60x with and w/o the extender btw - still a bit soft?

Joachim
 
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Guten Tag Herr Joachim!
Ja the world is different this last year and now, but birds - they don't care. Cannery Row wasn't very touristy because the Monterey Bay Aquarium has been closed this whole time. And the restaurants were closed. It was a disaster. The disaster is still unfolding.
But there are still lots of things to see. I work at Seaside High School, the rival of Monterey High School. My office steps out to a balcony from which I can see Lover's Point, about 4.2 miles (6.7km) so I thought "let me get a good scope so I can watch the swell come in." Turns out that I am expecting a lot from an 88mm scope, or perhaps any scope. I live in Carmel so I can also go down to Scenic Drive and look across to Point Lobos, and see the whales in the bay, and the seals, and the sea otters. And so many birds. The distances involved are longer from shore, so I feel like I need the sharpest instrument I can get so I can take photos and show them to students.

Maybe you heard of the Ghost Tree wave when you were here. The legendary Ghost Tree big surfing wave that rolls in and past Pebble Beach golf course. When the right swell comes it makes a barrel as long as a football field. From Carmel beach I can look across and see this wave, or from another angle at Pescadero Point directly opposite. Wave watching is also very interesting during winter.

I have soft examples with and without the extender, when using high magnification. Images in the midrange are wow!
I'm going to have to figure out a system for capturing photos quickly and reliably. Aber erste, eine neue scope sample.

Jordan
 

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jring

Well-known member
Hi Jordan,

yes, we heard a lot about Seaside High, just not good things as we usually had again been beaten by your team in some competition...

We often spent time at Lover's Point as my host family lived in PG. Unfortunately when I was there in march, it was too late for the Monarchs (but I saw some many years later in Central Park when I was on business in NY branch office).

I think, while people were surfing off the beaches of Pebble Beach and Carmel, Ghost Tree was not a thing back then - at least I haven't heard the name being used for a wave, just for the cypress trees along 17 mile drive... but I was not really into surfing and neither was my host family... parents were both teachers, dad taught biology at Monterey High...

Actually I think with a good scope it should be possible to judge the swell at 7km - provided the seing is ok... which it often is not on a nice day when you would want to go surfing... With my better than usual Kowa recognizing faces at 52x over 1km is quite possible - or identifying larger birds. But the highrise which I know to be 1km away from my balcony has more people on their balconies than birds...

Try to return that scope and I keep my fingers crossed that you get a better example...

Joachim
 

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