Moon - 2021-03-21 2357 UTC - Agrippa
This lunar image is about at good as its going to get for my location for two reasons. First is because of weather conditions, and second is because of the extremely fortunate timing of the Moon reaching its First Quarter phase at the vernal equinox.
My location is in central Maryland, where clear skies are rare, and clear skies with good seeing are even rarer. This image was taken on an exceptional March evening when the sky was crystal clear and the seeing was the best that I have seen here in a very long time.
In addition to having a great sky for imaging, the Moon was exceptionally well-placed for my location of 39.14N latitude. I captured this image just twelve minutes after the First Quarter Moon had transited the meridian at N25 degrees declination. This declination is about 14 degrees south of my zenith. At this high elevation above the horizon and with my observing site being 151 meters above mean sea level, the Moon's light passed through just 1.035 air masses.
The geometry of the celestial sphere that created this high-elevation transit is fascinating, and worth exploring.
The trace of the Sun's annual orbit among the fixed stars defines the ecliptic. The Moon’s orbit is inclined to the ecliptic by about 5.14 degrees, so it never wanders more than 5.14 angular degrees from it.
The reason for high-elevation lunar transit on the day of this image has to do with both the Sun’s and the Moon’s position on or relative to the ecliptic, and the Moon's position relative to the Sun. The Sun had arrived at the vernal equinox point on the ecliptic on this day, thus marking the first day of astronomical spring. In a quarter of a year from now, the Sun will have moved one quarter of the way around the ecliptic to arrive at the summer solstice point. This will be the day that the Sun passes overhead at its highest elevation each year.
The Moon, which is always situated near the ecliptic, was at First Quarter on this same day. This means that the Moon is one quarter of the way around it’s monthly orbit about the Earth since it was positioned in conjunction with the Sun just a week prior. This quarter orbit of distance from the sun put the Moon near the Sun’s summer solstice point on the ecliptic, which means the Moon was near its highest point of the year when it transits the meridian on this night.
This image is centered on the prominent crater Agrippa, which is located in the central lunar highlands between Mare Tranquilitatus to the East, and Sinus Medii to the west. Also present in this image are three extensive rille systems that stand out under the low Sun angle: Rima Ariadaeus to the north, Rima Hyginus to the northwest, and the extenisve Rimae Triesnecker to the west. Additional rilles can be found by zooming in and panning around.
ZWO ASI290MM
Meade LX850 (12" f/8)
Losmandy G-11
Autostakkert! (best 10% of 3,000 frames)
Moon - 2021-03-21 2357 UTC - Agrippa
This lunar image is about at good as its going to get for my location for two reasons. First is because of weather conditions, and second is because of the extremely fortunate timing of the Moon reaching its First Quarter phase at the vernal equinox.
My location is in central Maryland, where clear skies are rare, and clear skies with good seeing are even rarer. This image was taken on an exceptional March evening when the sky was crystal clear and the seeing was the best that I have seen here in a very long time.
In addition to having a great sky for imaging, the Moon was exceptionally well-placed for my location of 39.14N latitude. I captured this image just twelve minutes after the First Quarter Moon had transited the meridian at N25 degrees declination. This declination is about 14 degrees south of my zenith. At this high elevation above the horizon and with my observing site being 151 meters above mean sea level, the Moon's light passed through just 1.035 air masses.
The geometry of the celestial sphere that created this high-elevation transit is fascinating, and worth exploring.
The trace of the Sun's annual orbit among the fixed stars defines the ecliptic. The Moon’s orbit is inclined to the ecliptic by about 5.14 degrees, so it never wanders more than 5.14 angular degrees from it.
The reason for high-elevation lunar transit on the day of this image has to do with both the Sun’s and the Moon’s position on or relative to the ecliptic, and the Moon's position relative to the Sun. The Sun had arrived at the vernal equinox point on the ecliptic on this day, thus marking the first day of astronomical spring. In a quarter of a year from now, the Sun will have moved one quarter of the way around the ecliptic to arrive at the summer solstice point. This will be the day that the Sun passes overhead at its highest elevation each year.
The Moon, which is always situated near the ecliptic, was at First Quarter on this same day. This means that the Moon is one quarter of the way around it’s monthly orbit about the Earth since it was positioned in conjunction with the Sun just a week prior. This quarter orbit of distance from the sun put the Moon near the Sun’s summer solstice point on the ecliptic, which means the Moon was near its highest point of the year when it transits the meridian on this night.
This image is centered on the prominent crater Agrippa, which is located in the central lunar highlands between Mare Tranquilitatus to the East, and Sinus Medii to the west. Also present in this image are three extensive rille systems that stand out under the low Sun angle: Rima Ariadaeus to the north, Rima Hyginus to the northwest, and the extenisve Rimae Triesnecker to the west. Additional rilles can be found by zooming in and panning around.
ZWO ASI290MM
Meade LX850 (12" f/8)
Losmandy G-11
Autostakkert! (best 10% of 3,000 frames)