Event Date: May 6th
Time: 4:25(.42) AM
Brief
For at least one day during both March and April, I mentioned the loss of Neptune into the glare of the Sun. Now, as the solar system's most distant "classical" planet is rising about four minutes earlier each day (and the Sun only rising about 1 minute earlier each day), it has given Neptune a chance to be visible for a short time in western Aquarius; it rises about three hours before the Sun, meaning that for a little over an hour, it is visible in complete darkness and high enough out of atmospheric pollution to view. Here is Neptune well placed while the sky is still at its darkest; that being, just prior to the start of astronomical twilight. This first image shows that, with the ecliptic and celestial equator included. By putting them in, we see that the Sun is still far enough south to be affected by twilight early.
Time: 4:25(.42) AM
Brief
For at least one day during both March and April, I mentioned the loss of Neptune into the glare of the Sun. Now, as the solar system's most distant "classical" planet is rising about four minutes earlier each day (and the Sun only rising about 1 minute earlier each day), it has given Neptune a chance to be visible for a short time in western Aquarius; it rises about three hours before the Sun, meaning that for a little over an hour, it is visible in complete darkness and high enough out of atmospheric pollution to view. Here is Neptune well placed while the sky is still at its darkest; that being, just prior to the start of astronomical twilight. This first image shows that, with the ecliptic and celestial equator included. By putting them in, we see that the Sun is still far enough south to be affected by twilight early.
Detailed
Starting at about 4:30, our location on Earth is rotated enough towards the Sun, that it starts to slowly wash out the darkness of the sky. An hour later, Neptune can only be seen through powerful-enough telescopes, with the Sun getting closer to the horizon. As mentioned in the brief, astronomical twilight begins about 4:30 AM at this location, meaning that the Sun passes the 18º mark below the horizon. If you remember the celestial grid that I have often shown for planets and stars so far, it can be used for the Sun sub-horizon just as well as it can above the horizon. Astronomical twilight at this time of year lasts for a little over half an hour, until the Sun is 12º below the horizon. By this time, it is still almost too dark to see in a location with no other lighting, although the sky starts to reflect just enough blue light back to Earth for us to barely see. Then, nautical twilight begins, which is when we lose Neptune fast in binoculars and most small telescopes. This lasts until the Sun is 6º below the horizon, For the final "climb" of the Sun, only the brightest stars with an elongation large enough may be seen. As for us, it is light enough to walk around and do some activities.
As Neptune continues to rise a little earlier, and the Sun finally starts to rise later by Summer, we will see Neptune higher in the sky before Sunrise, and eventually far enough north of it by late fall that as an evening-viewed planet, it will be seen for hours.
This second image is good as reference for when Neptune is high enough above the horizon, with a 1º field of view. Although Aquarius' brighter stars are dim compared to the average apparent magnitude of other constellations', they can still be used to find Neptune. Remember that I talked about "star hopping"? By looking for patterns among stars, even if they are dim, they can help find dim Neptune, which doesn't look much bigger than a star in even medium-size 'scope. Look for triangle configurations, for example, with a near-equilateral one near Neptune as shown below, or the isosceles one near the top-left. The bigger the field of course, the more shapes can be seen, leading to more of a hopping project.
Starting at about 4:30, our location on Earth is rotated enough towards the Sun, that it starts to slowly wash out the darkness of the sky. An hour later, Neptune can only be seen through powerful-enough telescopes, with the Sun getting closer to the horizon. As mentioned in the brief, astronomical twilight begins about 4:30 AM at this location, meaning that the Sun passes the 18º mark below the horizon. If you remember the celestial grid that I have often shown for planets and stars so far, it can be used for the Sun sub-horizon just as well as it can above the horizon. Astronomical twilight at this time of year lasts for a little over half an hour, until the Sun is 12º below the horizon. By this time, it is still almost too dark to see in a location with no other lighting, although the sky starts to reflect just enough blue light back to Earth for us to barely see. Then, nautical twilight begins, which is when we lose Neptune fast in binoculars and most small telescopes. This lasts until the Sun is 6º below the horizon, For the final "climb" of the Sun, only the brightest stars with an elongation large enough may be seen. As for us, it is light enough to walk around and do some activities.
As Neptune continues to rise a little earlier, and the Sun finally starts to rise later by Summer, we will see Neptune higher in the sky before Sunrise, and eventually far enough north of it by late fall that as an evening-viewed planet, it will be seen for hours.
This second image is good as reference for when Neptune is high enough above the horizon, with a 1º field of view. Although Aquarius' brighter stars are dim compared to the average apparent magnitude of other constellations', they can still be used to find Neptune. Remember that I talked about "star hopping"? By looking for patterns among stars, even if they are dim, they can help find dim Neptune, which doesn't look much bigger than a star in even medium-size 'scope. Look for triangle configurations, for example, with a near-equilateral one near Neptune as shown below, or the isosceles one near the top-left. The bigger the field of course, the more shapes can be seen, leading to more of a hopping project.
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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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