Event Date: October 19th
Time: 7:00 AM/PM
Brief
About a month ago, I showed Arcturus setting, and mentioned its meaning as the "ghost" of the Sun. Now, the Sun has moved much further south of where Arcturus is in declination and therefore, the earlier Sunsets have made it seem as if Arcturus becomes visible at about the same altitude daily.
This first image shows the celestial grid to show both Arcturus' declination of 19º N, and that of where the Sun is relative to the celestial equator. Arcuturus is still 17º above the horizon at this time, and sets a little more than 1 1/2 hours later.
Detailed
Although Arcturus sets a little less than 4 minutes earlier each evening, it becomes visible about a minute and a half earlier with each passing evening. This latter scenario is a result of the evening daylight shortening; the western half of the sky becomes darker faster as the Sun dives below the horizon.
What is interesting is that although we see Arcturus set earlier, it is north enough that at this latitude, we can also see it before Sunrise, as the second image shows further down. Backing up 12 hours to 7 AM, with the sky still dark enough, the star is easily visibile. I kept the celestial grid in, to remind that the local path of Arcturus and other stars can be traced by looking at the celestial grid closest to them. When magnifying, sometimes I can get extra gridlines very close to stars to show the local path a little more accurately, in that manner.
Not long after the times shown for the images, there is a second for when they are precisely the same altitudes for a split second. Can you find out when that is, or at least guess, when seeing them in the morning and evening? In between seeing it rise and set, we have about 10 1/2 hours for when only a powerful telescope with clear enough skies can find the star...when the Sun lightens the sky!
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click on images to enlarge: courtesy of Starry Night Pro Plus, version 6.4.3, by Simulation Curriculum Corp.
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