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I'm recalling while taking a university astronomy class the professor brought a few of us up to the observatory, around sunset. He showed us a star near zenith with the telescope. After we left the observatory and were walking back to our dorms we thought we saw the same star, with the naked eye. The sky still seemed somewhat bright.

Is that possible?

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    $\begingroup$ Anything is possible, but a definitive answer will not be possible without knowing details such as the date (June? December? The stars visible are drastically different), time after sunset when the sky was still "somewhat bright" (is that 5 minutes after sunset or 60 minutes?), and the latitude (near the equator? Near the artic circle? It affects the length of twilight and stars visible.) It's also possible that you viewed a faint star with the telescope and a bright star later with the naked eye. Impossible to know? $\endgroup$
    – JohnHoltz
    Commented Oct 14, 2019 at 2:11
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    $\begingroup$ @JohnHoltz It was somewhere between late October and late November. 42.65° N. As I remember it was closer to 5 or 10 minutes after sunset, not 60, the sky still looked rather blue. The star we saw naked eye was generally in the same position as the star we observed through the telescope. I'm trying to remember if the professor pointed out the star, naked eye, while we were still on the roof of the physics building, and we found it again, once we left the building. $\endgroup$
    – Bob516
    Commented Oct 14, 2019 at 2:29
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    $\begingroup$ You can see bright stars in daylight with a telescope. Probably the sky darkened enough that you could spot it after sunset; it helps to spot a star in a relatively bright sky if you know exactly where to look. $\endgroup$
    – antlersoft
    Commented Oct 14, 2019 at 2:41
  • $\begingroup$ livescience.com/34335-see-stars-daytime.html is a google link. I've seen Venus in the daytime myself, but nothing else. $\endgroup$
    – user21
    Commented Oct 14, 2019 at 16:58

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Is that possible?

Yes!

  1. You can see bright stars and planets through a telescope in the evening and in some cases during the day. As magnification increases the brightness of the sky or any extended object decreases with the square of the magnification. For example, a patch of sky will have a certain brightness per square degree, but at 100x magnification it will be 10,000 times dimmer.
  2. A star will (roughly speaking) be simultaneously brighter by the ratio of the square of the telescope's diameter to your pupil (which is 6 millimeters or less), so an 6-inch (15 cm) diameter telescope will make the star look 625 times brighter.
  3. When it got dark, the sky naturally became far dimmer, and your pupils dilated to larger diameters, making the star brighter.

So you can think of the two methods (viewing through telescope versus waiting for night) as similar, in that they both make the sky dimmer and the star brighter.

It's possible to start guessing what that star might be, but I don't know. Here are two predictions of the sky on November 15 at 5:30 PM and 8:30 PM local time at roughly 42 degrees North latitude.

That far North there are no planets that could be very close to the zenith, and it would be necessary to know the year as well to see how close one might have gotten.

Images are from in-the-sky.org's planetarium feature.

enter image description here

enter image description here

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