For the Higher Positions from the Horizon: Starrise or Star Showing Up?

In the night, the stars at higher position from the horizon, which one is the case?

1. They are already visible from the beginning/from horizon.
2.  They show up from the darkness at certain height..

Thanks for the answer. 

3. They are there, some all the time, but are only recognisable as the sky darkens.

They don't appear from the darkness, they remain as the sky goes dark and your eyes adjust.

To Danang I would say this:

1 and 2 are both partially true.  Light pollution and/or atmospheric transparency both have an effect on how well the stars can be seen lower down towards the horizon.

The degree of refraction of starlight varies (increases) with distance from higher up to lower down in the sky and software that I use to control my telescope mount uses an all sky mapping system which compensates for this.  I could write a book about how this works but I will spare you the details.

In reality the discrepancy between actual and observed position of a star is very small but is nevertheless significant in long exposure imaging.

One really neat thing that relatively few people ever get a chance to really see and appreciate is related to seeing stars during a solar eclipse. Let's say it is summer for you and you're in the path of totality for a solar eclipse. When the sun is covered by the moon, you can see stars during the daytime. And here's the neat thing: the stars you see are the stars you would normally see during the winter. They are there, all year long. It's just that for roughly half the year, the sky is too bright to be able to see them.

Absolutely.  And if you have a permanently mounted and aligned telescope you can look at stars 'out of season' whenever you want.

Cool 👍

I'm listening