M101 Unfiltered - annotated · 2025-06-25

The Pinwheel Galaxy M101 (or NGC 5457) as seen from my backyard.

The Pinwheel Galaxy M101 (or NGC 5457) as seen from my backyard. The Pinwheel Galaxy is a face-on, counterclockwise intermediate spiral galaxy located 21 million light-years (6.4 megaparsecs) from Earth in the constellation Ursa Major. It was discovered by Pierre Méchain in 1781 and was communicated that year to Charles Messier, who verified its position for inclusion in the Messier Catalogue as one of its final entries.M101 is a large galaxy, with a diameter of 252,000 light-years. By comparison, the Milky Way has a diameter of 87,400 light-years. It has around a trillion stars. It has a disk mass on the order of 100 billion solar masses, along with a small central bulge of about 3 billion solar masses.

The next image shows annotated view of its location.

Exposure	47 x 600 sec = 7.83 hours
Gain	100
Camera	ToupTek ATR2600C [6224 x 4168]
Optics	Skywatcher Esprit 120mm
Filter	None
Capture	KStars on Unbuntu 24.04 on a Mele Quieter 4C
Location	Lower Sackville, Nova Scotia.
Date	2025-06-25,27
Processing	Processed in PixInsight.
SetiAstro Automatic DBE, SpectrophotometricColourCalibration, BlurXTerminator, NoiseXTerminator, Generalized Hyperbolic Stretch (GHS) (using Blair MacDonald's excellent YT Tutorial), StarXTerminator, PixelMath recombination ~((~stars)*(~starless)), Annotate Image