Messier 101 (Pinwheelgalaxy)

I imaged Messier 101 (M101) twice from my backyard—first in 2005 using my very first DSLR setup, and again in 2011 with the same telescope but a newer DSLR camera and significantly longer total exposure time. Both attempts already revealed the galaxy’s sprawling structure, but the real leap in quality came in 2019, when I received a deep dataset from Deep Sky West (DSW) in New Mexico. The DSW data, taken under pristine skies with a highly sensitive CCD system, captured the enormous extent of M101’s outer spiral arms, its asymmetric structure shaped by past interactions, and the wealth of H II regions scattered throughout the disk.

Scientifically, Messier 101, also known as the Pinwheel Galaxy or NGC 5457, is one of the largest and most detailed face-on grand-design spiral galaxies observable from Earth. Located about 21 million light-years away in Ursa Major, it spans an impressive 170,000 light-years, making it noticeably larger than the Milky Way. Its spiral arms are rich in star-forming regions—several of them among the brightest known in any nearby galaxy—and its slightly distorted shape hints at gravitational interactions with its satellite galaxies. Deep exposures often reveal an extended, faint stellar halo and tidal structures, making M101 an especially rewarding long-exposure target.

The combination of my early backyard attempts and the deep DSW dataset nicely illustrates just how much detail and faint structure can be uncovered with improved equipment, darker skies, and more exposure time.

Data calibration and registration and the final processing was done with PixInsight. Hα was assigned to the red channel. The result was as follows:

Messier 101 - Pinwheel Galaxy (Feuerrad-Galaxie), (DSW), New Mexico, 2019 — Messier 101 – Pinwheel Galaxy (Feuerrad-Galaxie), (DSW), New Mexico, 2019

The faintest star in this image has an apparent magnitude of 22.1 mag_G (SDSS DR15).

Beside M101 there are a lot of background galaxies in the image. Furthermore I marked the two most distant quasars:

The two highest redshift quasars [Flesh 2015] in the image are:
SDSS J140529.74+540159.7 z=3.99 mag_G=21.1 (Gaia DR2)
SDSS J140053.75+543012.1 z=4.17 mag_G=20.0 (Gaia DR2)

The images were taken with the following equipment:

Date: 2019
Location: Rowe, New Mexico
Telescope/Lens: Takahashi FSQ-106
Focal length [mm]: 530
Focal ratio: 5
Mount: Paramount MyT
Camera: QSI 683-WSG-8
Filter: L:Hα:R:G:B
Exposure time [min]: 350:480:330:280:390
Resolution: 2.08″/px

For the 2011 data the calibration and registration was performed with DeepSkyStacket, the final processing was done with PixInsight. The result was as follows:

The images were taken with the following equipment:

Date: 2011
Location: Krefeld, Germany
Telescope/Lens: 8″ GSO Newton
Focal length [mm]: 800
Focal ratio: 4
Mount: Skywatcher NEQ6
Camera: Canon 500Da
Filter: no
Exposure time [min]: 480
Resolution: 1.19″/px

For the 2005 data the calibration and registration was performed with DeepSkyStacker, the final processing was done with PixInsight. The result was as follows: