Observation by Peter Hannah: M101

Uploaded by

Peter Hannah

Observer

Peter Hannah

Observed

2025 Sep 12 - 00:00

Uploaded

2025 Sep 18 - 11:15

Objects

M101

Equipment

Planewave CDK 14 Corrected Dall-Kirkham
ZWO ASI6200 camera
10Micron GM2000 mount
Astrodon RGB & H-alpha filters

Exposure

Red 6hrs, Green 5hrs, Blue 5hrs, H-a 5.5hrs

Location

Oria, Spain

Target name

M101

Title

M101

About this image

Known as the Pinwheel Galaxy, M101 is a face-on spiral some 21 million lightyears away in the direction of Ursa Major. It can be found fairly easily with binoculars as it forms the vertices of an equilateral triangle with the first two stars of the handle of the Plough - Alkaid and Mizar.

Its diameter is estimated at over 170,000 lightyears, almost twice that of the Milky Way, and it has many ionized hydrogen (H-II) regions, some of which have been assigned their own NGC numbers.
The image shows the red glow of the H-II regions which contrasts with the blue spiral arms, the latter a sign of active star formation. This is assumed to be due to gravitational interactions with M101's companion galaxies compressing the interstellar hydrogen gas, thus stimulating star formation.

Processing this image was fairly straightforward in PixInsight. Preparation for adding the H-alpha signal required subtracting the Red filter's continuum background first, but PixInsight has a tool to facilitate this.

Files associated with this observation

M101_HaRGB_final_compressed.jpg (9.7 MB)

Like this image

Graham Winstanley, Dominic Ford

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