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Star-test results ?

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Old Tuesday 22nd January 2013, 21:00   #1
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Star-test results ?

Have you star-tested your scope?

It seems there are very few star-test results presented, preferrably with a photo, here at BF.

Are you not interested in how your scope performs?

It would be very kind if you would like to share the result with us if you have done it or will do it.

I am in the process of buying a scope for the first time so this would be very interesting to me

Test results from different scopes of the same type would also be interesting concerning QC.

Have you heard of any manufacturer that do this test on each (some?) scope as a QC approval to pass inspection ?

Here is a thread with some general info from HenryLink: http://www.birdforum.net/showpost.ph...75&postcount=8

Here is some more:
http://www.spacealberta.com/equipmen...r/startest.htm

When the time comes and I have bought a new scope I will try to star-test it so I can return it if it is a lemon, wouldn´t you

Many thanks to those that will share!

Anders
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Old Tuesday 22nd January 2013, 22:38   #2
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Some more general info:

http://aberrator.astronomy.net/
http://www.telescope-optics.net/diff...berrations.htm
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Old Wednesday 23rd January 2013, 06:32   #3
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LS, thanks for the links!

Anders
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Old Wednesday 30th January 2013, 19:50   #4
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Can star test results vary if we change an eyepiece?
Or it is a function of front lenses only.

Mariusz
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Old Wednesday 30th January 2013, 21:17   #5
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Mariusz,

Unless the eyepiece is grossly defective, the star-test results will be influenced only by the scope. But different eyepieces have different magnification, and to evaluate a star-test properly you need lots of magnification. So, unless you use a booster scope behind the eyepiece, you will see only the larger defects with an eyepiece that gives much less than 1x/mm of aperture.

In your question you say "function of front lenses only." The parts of the scope that influence the star-test include the objective group, a focussing group if there is one, and the prism assembly. All of these have to be flawless for a perfect scope, but usually the biggest visible problems come from the objective group, with the focussing group sometimes causing coma and less often some slight pinching, and a poorly ground roof prism potentially causing a diagonal fuzzy line to cross an out-of-focus diffraction pattern.

Kimmo
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Old Thursday 31st January 2013, 19:34   #6
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Kimmo,

if we need a booster to see faults, maybe for a regular user star test is not much o a value.

Suppose a scope shows faults in star test. Can we see it with a naked eye? How it impacts our view in the fields?

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Mariusz
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Old Thursday 31st January 2013, 21:53   #7
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Mariusz,

You need the booster to analyze the faults in order to know what they are and to roughly quantify them, but their effects are unfortunately all too easily seen with the naked eye in the field.

Kimmo
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Old Saturday 2nd February 2013, 22:36   #8
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Found this on Zen Ray homepage....

Every single set of ZEN ED2 spotting scope will go through our rigorous star testing (the first in industry) procedure to ensure picture perfect experience for our users.

I wonder what the criterias for "passed" are since there is no established standard ? Photos of the individual test result, delivered with the scope, would be nice.

Well, I think it is great that ZR is improving QC, maybe the "others" have to follow to keep up :-)

Found this: http://seanghor.files.wordpress.com/...op-testing.pdf
Check chapter 11 concerning star test.

Anders

Last edited by Binoseeker : Sunday 3rd February 2013 at 20:09.
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Old Tuesday 5th February 2013, 18:04   #9
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Quote:
Originally Posted by Binoseeker View Post
Found this on Zen Ray homepage....

Every single set of ZEN ED2 spotting scope will go through our rigorous star testing (the first in industry) procedure to ensure picture perfect experience for our users.

I wonder what the criterias for "passed" are since there is no established standard ? Photos of the individual test result, delivered with the scope, would be nice.

Well, I think it is great that ZR is improving QC, maybe the "others" have to follow to keep up :-)

Found this: http://seanghor.files.wordpress.com/...op-testing.pdf
Check chapter 11 concerning star test.

Anders
Anders,

This is the best book.

https://www.willbell.com/tm/tm5.htm

But you do need to keep in mind that all the images there are computer simulated.

Charles
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