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New Kowa 883 (1 Viewer)
- Thread starter andyF
- Start date
Andy - this is a scope that is very much on my radar at the minute so a few questions if I may...
Sounds like you bought it sight unseen...? Ordered online I presume
You say "package" - scope + zoom eyepiece + stay-on case? That's the typical bundle I have seen for this
Can I ask what you paid, if you don't mind?
Sounds like you bought it sight unseen...? Ordered online I presume
You say "package" - scope + zoom eyepiece + stay-on case? That's the typical bundle I have seen for this
Can I ask what you paid, if you don't mind?
Package consisted of scope + wide zoom (20-60x) + stay-on case. Bought from Cley Spy at £1999. Ordered 27th and was delivered 28th free of charge. I've tested it and it seems to be free of any defects (there seems to be some dust issue that had been reported a short time back). I'm going to Brandon Marsh this weekend to give it a full runout.
Do you mean the 25-60 wide zoom? If so there have been reports of issues with internal specks showing at certain magnifications, apparently now cured on new stock.
henry link
Well-known member
Here's a link to an old thread about testing two Kowa 883s.
http://www.birdforum.net/showthread.php?t=125302
I would never buy a scope without star-testing it, but I've mostly stopped recommending star-testing to people who have never done it. I found out that, for beginners, there are many ways to do it wrong or misinterpret the results. Nevertheless, it's the only way I know for a consumer to tell exactly how good a particular scope specimen is and exactly what's wrong with it if it's defective.
FWIW I found two of six 883s I tested to be what I consider optically unacceptable. I don't think other brands do any better. It's best to assume guilt until innocence is proven.
If you want to give it a try there is plenty of information online about how to conduct a star-test, just google something like "telescope star test".
http://www.birdforum.net/showthread.php?t=125302
I would never buy a scope without star-testing it, but I've mostly stopped recommending star-testing to people who have never done it. I found out that, for beginners, there are many ways to do it wrong or misinterpret the results. Nevertheless, it's the only way I know for a consumer to tell exactly how good a particular scope specimen is and exactly what's wrong with it if it's defective.
FWIW I found two of six 883s I tested to be what I consider optically unacceptable. I don't think other brands do any better. It's best to assume guilt until innocence is proven.
If you want to give it a try there is plenty of information online about how to conduct a star-test, just google something like "telescope star test".
hi henry
the only thing i don't understand is how is it possible to do a star test on a scope before buying it?
not sure about elsewhere, but in the uk i can't see any shops/retailers etc breaking the seal on a brand new scope to let me test it before i hand over the cash, let alone trying 2 or 3 so i can decide.
i may wait and go to the birdfair instead. i may have more chance to try there
before buying. but i dunno
if i just buy one and find it's a lemon, do you think kowa would play ball and exchange for another?
do you get to test them first and how?
You have consumer rights for anything you buy, if it is defective. A return for a replacement should be no problem. (I've just received a refund for a car of a heck of a lot more than a scope after problems developed five weeks after purchase, although I suspect that is fairly unprecedented.)
I don't think many scopes are sealed in the supplied box. Certainly when I was going to switch to a straight Nikon fieldscope from angled I asked Uttings online if I would be able to return a poor sample and they said yes as they weren't in a sealed box. For multiple returns I would have had to pay postage.
I think receptive retailers would let you exchange a below par specimen if you checked with them beforehand.
Cley Spy in Norfolk had/have? a resolution chart on the wall which allows you to compare models and are very helpful.
At Minsmere in Suffolk I can star test models on a ceiling light reflection but this isn't much use as you are in Lancashire. I'm an Optics Volunteer there.
Personally I find the Birdfair a bit of a scrum and not ideal to purchase optics. I'd rather try on a quiet reserve or shop.
"I've tested it and it seems to be free of any defects"
andyf
how did you test it out of interest?
where do i get a res chart for testing.
how do you (or anyone) define a good kowa 883 by looking
at the res chart, is there a certain reading/measurment on the chart that the scope
can resolve that says - yep this is a good one!
andyf
how did you test it out of interest?
where do i get a res chart for testing.
how do you (or anyone) define a good kowa 883 by looking
at the res chart, is there a certain reading/measurment on the chart that the scope
can resolve that says - yep this is a good one!
You can print this one out http://accurateshooter.net/targets/usaf1951.pdf
With testing a scope you should be able to snap into focus at 60x easily. Ideally you want to be able to compare a number of samples of the same scope and pick the the one that resolves best. However you still won't know if you have bought the best aberration free specimen of the model of scope unless you can star test it.
Hope this helps.
dipped
how much of that chart should a good 883 resolve though?
post 3 on this link shows horizontal bars @12.5 being resolved but not vertical bars.
http://www.birdforum.net/showthread.php?t=125302
i'm just not sure how to interpret what the chart shows.
so print this on a4 at 40 metres and 60x mag, would this be right?
thanks
Hi,
I for my part would not consider buying optics in a sealed box at a store. Either it's online with the mandatory 2 week return policy over here or in a store I'll test it and then nicely ask to keep the sample I have had a closer look at. Sometimes I even get a slightly lower price for the demo...
Regarding star testing - the easiest way is of course at night but in a store, you could to bring an artificial star to the store - you can DIY by placing some aluminium foil on a glass surface and very slightly perforate it with a thin needle. Make sure not to tear it as it should be round.
When you have a strong LED light behind it, you should see a very tiny light spot. If you now tape the aluminium foil in front oft the LED light and put the whole contraption somewhere 20 or 30m away from the scope, you can then look at the light spot with the scope at maximum magnification. In focus it should be a tiny bright spot with very faint rings around it, but we are looking for the image slightly out of focus. Ideally this is done on a cool day without sun heating up the air.
There's been written at least one book on star testing, possibly more and most books on telescope making contains a chapter on it.
http://www.telescope-optics.net/star_testing_telescope.htm
has a lot of calculations on the correct size and observing distance for an artificial star - a tiny pin ***** in aluminium foil should be 50 micron or lower and >20m distance should be plenty for a 3-4" ED APO.
In the lower section it has simulated images for perfect optics and various aberrations. A small refractor should be very close to perfect.
Joachim
Last edited:
In a way what you're asking is a) what is the theoretical resolving power of an 88mm telescope b) how close would an acceptable Kowa get and c) how will I know if I have an acceptable Kowa specimen.
I'm sure the info is out there somewhere for a and b but to be honest you want to know c. So if I were you I would print the chart out and use it to discriminate between samples of the same model or similar speced models under similar conditions.
Here's a link to Kimmo's test of the Kowa 883. There are also other articles which talk about resolution testing of scopes which should be of use.
http://www.lintuvaruste.fi/hinnasto/optiikkaarvostelu/optics_13_kowa883_GB.shtml
Vespobuteo
Well-known member
here is a comparison between 883 and ATX95, in french but use google translate
http://www.topoptics.biz/Technique/Bras-de-fer/SwaroATX95-vs-KowaTSN883.htm
this is interesting also, many scopes tested here (but not the latest 25-60x Kowa zoom unfortunately)
http://www.tvwg.nl/ovz-telescopen.shtml
http://www.topoptics.biz/Technique/Bras-de-fer/SwaroATX95-vs-KowaTSN883.htm
this is interesting also, many scopes tested here (but not the latest 25-60x Kowa zoom unfortunately)
http://www.tvwg.nl/ovz-telescopen.shtml
Nisus,
It is unfortunately not possible to say how much of a given chart at a given distance a good scope should resolve, since this does not depend only on the scope but also on the visual acuity of the observer. A skilled observer will have a pretty good idea based on their experience what a scope of a given size should be capable of resolving to their eyes, and if a skilled observer reports their findings from sufficiently standardized distances, illumination levels and non-interfering atmospheric conditions, then that observer's findings can be compared with each other, but not directly from observer to observer.
Rather than fretting over which pattern you can resolve and which not, it is better to concentrate on how sharp the image appears to your eyes, and how easily and quickly you can reach best focus each and every time you focus the scope at its maximum magnification.
Those who have good samples of a given scope often use them also at their maximum magnifications, and may wish for more magnification than the scope can give. Those with sub-par samples find themselves hardly ever using the maximum magnification and they often state that such high magnifications are unnecessary or useless.
Kimmo
It is unfortunately not possible to say how much of a given chart at a given distance a good scope should resolve, since this does not depend only on the scope but also on the visual acuity of the observer. A skilled observer will have a pretty good idea based on their experience what a scope of a given size should be capable of resolving to their eyes, and if a skilled observer reports their findings from sufficiently standardized distances, illumination levels and non-interfering atmospheric conditions, then that observer's findings can be compared with each other, but not directly from observer to observer.
Rather than fretting over which pattern you can resolve and which not, it is better to concentrate on how sharp the image appears to your eyes, and how easily and quickly you can reach best focus each and every time you focus the scope at its maximum magnification.
Those who have good samples of a given scope often use them also at their maximum magnifications, and may wish for more magnification than the scope can give. Those with sub-par samples find themselves hardly ever using the maximum magnification and they often state that such high magnifications are unnecessary or useless.
Kimmo
Boy Wonder
Warden - RSPB Lincolnshire Wash Reserves
Not really about testing, more just getting the best from your scope...... highly recommend the 1.6 extender. I have sold three indirectly through showing people mine and a friend went out and bought the whole package on using the extender on my scope. Really does get the best out of what is great bit of kit.
