M81, otherwise known as Bode’s Galaxy (right) and M82 otherwise known as Cigar Galaxy (left), are two galaxies in the Ursa Major constellation (home of the Big Dipper), located approximately 12 million light-years away from Earth. As neighbors, they share a fascinating history, marked by interactions and mutual influence. Over time, M81 and M82 have interacted with each other because of their proximity, with their gravitational attraction affecting the structure and star formation processes in both galaxies. Around 100-200 million years ago, the two galaxies underwent a close encounter, causing M81’s gravitational pull to strip gas and dust away from M82. This event ignited intense star formation in M82, transforming it into a starburst galaxy, which is visually apparent because of the amount of Hydrogen Alpha–the intense red in the galaxy. The interaction also caused tidal forces to warp M81’s spiral structure and triggered star formation in its outer arms, which you can see by the red rings in its spiral arms.
M81 is home to a supermassive black hole, approximately 70 million times the mass of our Sun, at its core. This black hole is actively consuming material from its surroundings, releasing powerful jets of energy. M82 is known for its intense starburst activity, with stars forming at a rate 10 times greater than in our own Milky Way galaxy. This rapid star formation generates powerful winds that blow gas and dust out of the galaxy, as you can see with the “red wings” that are extending off M82.
In the next few billion years, their continuing gravitational encounters will cause a merger, and a single galaxy will remain.
About This Photo
If you’ve explored this site, you know I live in a light-polluted area right outside New York City. Taking photos of galaxies should not be a thing for me.
To mitigate my light pollution issue, I planned well. I took this picture near the meridian which has less light-pollution. I also obviously imaged on moonless nights. However, tools like dynamic background extraction have really helped effectively eliminate any light pollution in my photos.
I spent hours researching and trying techniques of how to add Ha to a galaxy. To my surprise, it wasn’t as easy as I thought it would be. I tried Visible Dark’s simple technique several times, but it wasn’t working out as I wanted it to. I then tried James Lamb’s technique, which worked for the first time. This technique was more laborious, but it worked much better. I referenced this video by Paulyman Astro which explains James Lamb’s technique very well.
Unfortunately, I could only get about 13 hours of data. Almost 7 hours of it is luminance with 4.5 hrs of RGB and almost 2 hours of Ha.
I want to shoot more luminance to bring out the Flux Nebula that surrounds and connects both galaxies; this photo has a bit. To do so, it will probably take another 5-7 hours of data for that to more prominently appear.
Another issue is the star color. The stars are boring white. I may need to re-do this to figure out where that went wrong, but at this point–I’ll live with it. I am obsessive compulsive, so I’ll probably have another revision for this in the future.
Pixinsight Steps & Data
Here are the steps that I took in Pixinsight to do this. I brought this into Photoshop for resizing and cropping only and did not make any further adjustments there.
Linear
- Dynamic Crop on all channels separately
- DBE on all channels separately (R, G, B, L, Ha)
- Blur Xterminator on all channels
- Noise Xterminator on all channels
- Combine Ha with the red channel as outlined in this video
- Channel Combination for R, G,B using the new red I created that combines Ha data
- Image Solver
- Spectrophotometric Color Calibration
- SCNR (to remove the green cast)
- Masked Stretch to RGB
- Masked Stretch to Luminance
Non-Linear
- LRGB Combination adding the Luminance into the RGB
- Star Xterminator
- Color Saturation
- Multiple Curves Transformations
- Local Histogram Equalization
- More Curves Transformations
- Noise Xterminator
- Unsharp Mask
- Pixel Math to add the stars back in
- Final Curves Transformation to add contrast
| Filter | Hours |
|---|---|
| Red | 1h 39m (99 x 60s) |
| Green | 1h 27m (87 x 60s) |
| Blue | 1h 29m (89 x 60s) |
| Lumianance | 6h 39m (399 x 60s) |
| Ha | 1h 54m (38 x 180s) |
| TOTAL | 13h 8m |