What is the apparent magnitude limit for the naked eye?

  • If you only read the question, you will answer: ''That depends on the light pollution''. Yes, it does, but if you are in the darkest night sky (Bortle class 1), what magnitude would have the faintest star? In the Wikipedia article about the magnitude, it's written that +6.0 would be the typical limit, but in the article about the Bortle scale, I saw the fainter magnitude +8.0. So, what is the real limit?

    If the question has been already asked, please give me the link.

  • The apparent magnitude classification was done arbitrarily by Ptolemy. His thought was to set the 20 brightest stars to the first position, the less bright stars to the second position and so on up to the faintest stars which were given the sixth position. After the use of Pogson's law we were able to give to stars not only natural numbers, but also numbers with decimal digits. When we started to use the first telescopes, we realised that the numbers which are greater than 6 have meaning. So the natural limit of naked eye is the apparent magnitude of +6. Here you can find a nice work from the italian Light Pollution Science and Technology Institute which shows as the typical limit of naked eye compared to the light pollution of each area.

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Content dated before 7/24/2021 11:53 AM