Messier 3
Messier 3 (M3; also NGC 5272) is a globular cluster located 33.9 thousand light years from Earth in the northern constellation of Canes Venatici. It is one of the largest and brightest globular clusters discovered with around 500,000 stars.
It was discovered on May 3, 1764 and was the first Messier object to be discovered by Charles Messier himself. Messier originally mistook the object for a nebula without stars. This mistake was corrected after the stars were resolved by William Herschel around 1784. Since then, it has become one of the best-studied globular clusters. Identification of the cluster's unusually large variable star population was begun in 1913 by American astronomer Solon Irving Bailey and new variable members continue to be identified up through 2025.
Many amateur astronomers consider it one of the finest northern globular clusters, following only Messier 13. M3 has an apparent magnitude of 6.2, making it a difficult naked eye target even with dark conditions with averted vision. However, with a moderate-sized telescope, the cluster can be seen as a cloudy smudge even in severely light-polluted skies, and can be further defined in darker conditions. It can be found by looking almost exactly halfway along the north-west line that would join Arcturus (α Boötis) to Cor Caroli (α Canum Venaticorum).
Imaging telescope: Takahashi FSQ130ED
Imaging camera: ASI 2600MM
Mount: JTW Trident P75
Guiding telescope: Takahashi FS60CB
Guiding camera: ASI 678 MM (BIN 2)
Focal Extender / Reducer: None
Software: Sequence Generator Pro SGP (for capture) PHD 2 (guiding), Astro Pixel Processor, PixInsight.
Filters: Astrodon RGB.
Accessories: Robofocus Focuser controlled by Lunatico Armadillo, ATIK EFW 3, RB Focus Gaius S2, RB Focus Excalibur.
Dates: 12th May 2026
Frames:
Astrodon RGB 3 x 60 x 1'
Total integration = 3 Hours.
Center (RA, Dec): (205.466, 28.384)
Center (RA, hms): 13h 41m 51.777s
Center (Dec, dms): +28° 23' 03.728"
Size: 89.6 x 59.7 arcmin
Radius: 0.897 deg
Pixel scale: 1.19 arcsec/pixel
"Orientation": Up is 89.2 degrees E of N
It was discovered on May 3, 1764 and was the first Messier object to be discovered by Charles Messier himself. Messier originally mistook the object for a nebula without stars. This mistake was corrected after the stars were resolved by William Herschel around 1784. Since then, it has become one of the best-studied globular clusters. Identification of the cluster's unusually large variable star population was begun in 1913 by American astronomer Solon Irving Bailey and new variable members continue to be identified up through 2025.
Many amateur astronomers consider it one of the finest northern globular clusters, following only Messier 13. M3 has an apparent magnitude of 6.2, making it a difficult naked eye target even with dark conditions with averted vision. However, with a moderate-sized telescope, the cluster can be seen as a cloudy smudge even in severely light-polluted skies, and can be further defined in darker conditions. It can be found by looking almost exactly halfway along the north-west line that would join Arcturus (α Boötis) to Cor Caroli (α Canum Venaticorum).
Imaging telescope: Takahashi FSQ130ED
Imaging camera: ASI 2600MM
Mount: JTW Trident P75
Guiding telescope: Takahashi FS60CB
Guiding camera: ASI 678 MM (BIN 2)
Focal Extender / Reducer: None
Software: Sequence Generator Pro SGP (for capture) PHD 2 (guiding), Astro Pixel Processor, PixInsight.
Filters: Astrodon RGB.
Accessories: Robofocus Focuser controlled by Lunatico Armadillo, ATIK EFW 3, RB Focus Gaius S2, RB Focus Excalibur.
Dates: 12th May 2026
Frames:
Astrodon RGB 3 x 60 x 1'
Total integration = 3 Hours.
Center (RA, Dec): (205.466, 28.384)
Center (RA, hms): 13h 41m 51.777s
Center (Dec, dms): +28° 23' 03.728"
Size: 89.6 x 59.7 arcmin
Radius: 0.897 deg
Pixel scale: 1.19 arcsec/pixel
"Orientation": Up is 89.2 degrees E of N
Sky Map & Finder Chart
Annotated Image
