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I found an used Skywatcher 70mm telescope for buying, but its lenses are a little suspect about harming. In one photo, it looks clearly a scratch, but in the another, it is not visible. Could it be an optical illusion or is it really a harm? If it's a scratch, should I discard the possibility of buying?

Lens apparently dirty and harmed, with a visible line crossing the glass

The same lens, apparently clear and perfect

Pointing where I think there are scratches: scratch img1

scratch img2

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  • $\begingroup$ Could you point out where you see the scratch? $\endgroup$ – usernumber Jan 8 '20 at 16:49
  • $\begingroup$ I added to the post the same two images with some indication, hope it help $\endgroup$ – Vitor Z. Jan 8 '20 at 17:22
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    $\begingroup$ The big ones at the top seems to be just a reflection, not a scratch. $\endgroup$ – usernumber Jan 8 '20 at 17:45
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Price vs. quality. You're unlikely to see any significant degradation in the final image if those are scratches. However, that is not how you should make your purchase decision. You want to inspect the entire body for any evidence of dents, bends, etc. which indicate rough usage, not to mention misalignment of the optical elements.

If you can't try out the 'scope in person, make sure there's a 100% refund guarantee before having it shipped to you.

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  • $\begingroup$ Does misalignment in refractor telescopes exist? If, how can I detect it? Is it common? Could it be fixed? $\endgroup$ – Vitor Z. Jan 8 '20 at 18:43
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    $\begingroup$ @VitorZ. if the barrel is bent, then it's misaligned :-) . Otherwise unlikely that optical elements have shifted. But if you focus at infinity and the images are more elliptical than circular, that suggests some misalignment. $\endgroup$ – Carl Witthoft Jan 8 '20 at 19:52

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