Before joining this forum it never crossed my mind that the scope I bought could be defective ( a Lemon ) Whenever I buy anything I always buy quality and I must admit, I am surprised that the quality of spotting scopes, especially from world class optic manufactures are subject to quality variations.
What is it that make these Lemons defective? Is it the lenses, alignment or something else. Are these top end optics not checked before they are sent out, surely they would have some means of checking them?
Personally I've always been happy the optics I've bought, and I have to admit I'm a bit sceptical that there are that many out there that you need to do a star test before you buy.
Just spotted this.
Star testing a telescope can be a great way to determine if any errors are present in the optical system and what those errors are. The star test is very critical and can show even slight aberrations. It does require a sharp eye and some experience to really get the most out of it. This section will describe how to star test a telescope and give examples of the most common aberrations. For more details on the errors you might see, check out the Optical Aberrations page.
Note: First a warning. The images shown below are idealized examples. Unless you paid as much as a small car and waited on a list for the better part of a decade to get your telescope, do not expect flawless optics. Most mass produced telescopes--even good ones--can show minor flaws if you look closely enough. The real test of a telescope is what you see when you look through the eyepiece under normal conditions. Almost without exception, all telescopes from reputable manufacturers will perform well enough that you could never notice any errors. If you plan on using your telescope to look at high-power, out-of-focus star images, maybe a star test is a practical examination of the scope's optics. But in reality, as long as the telescope shows good images under normal use, a star test doesn't mean too much. However, for advanced users who want to compare different instruments or determine what the limiting factors of their optics may be, the star test is a great way to learn a lot about a telescope.
What is it that make these Lemons defective? Is it the lenses, alignment or something else. Are these top end optics not checked before they are sent out, surely they would have some means of checking them?
Personally I've always been happy the optics I've bought, and I have to admit I'm a bit sceptical that there are that many out there that you need to do a star test before you buy.
Just spotted this.
Star testing a telescope can be a great way to determine if any errors are present in the optical system and what those errors are. The star test is very critical and can show even slight aberrations. It does require a sharp eye and some experience to really get the most out of it. This section will describe how to star test a telescope and give examples of the most common aberrations. For more details on the errors you might see, check out the Optical Aberrations page.
Note: First a warning. The images shown below are idealized examples. Unless you paid as much as a small car and waited on a list for the better part of a decade to get your telescope, do not expect flawless optics. Most mass produced telescopes--even good ones--can show minor flaws if you look closely enough. The real test of a telescope is what you see when you look through the eyepiece under normal conditions. Almost without exception, all telescopes from reputable manufacturers will perform well enough that you could never notice any errors. If you plan on using your telescope to look at high-power, out-of-focus star images, maybe a star test is a practical examination of the scope's optics. But in reality, as long as the telescope shows good images under normal use, a star test doesn't mean too much. However, for advanced users who want to compare different instruments or determine what the limiting factors of their optics may be, the star test is a great way to learn a lot about a telescope.
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