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M99 & M100 - Astrophotography Tips for a Field of Galaxies

Updated: May 18, 2023

Messier 99 and Messier 100 are two grand design spiral galaxies located in a busy area of Coma Berenices. M99 and M100 are both beautiful objects, and they lie very close to many other galaxies.

We imaged these galaxies from our usual Bortle 4 spot, one hour north of Las Vegas. Midway through the night, our Intel Nuc computer attached to our telescope decided to glitch and crash. This happened when we were both asleep in the trunk of the car. I woke up at 2 AM, sensing that something terrible had happened. I realized that the computer crashed and went out in the cold to reboot it.

I was very sleepy and just launched SGP/PHD2 very quickly before going back to sleep. Back at home, half of the data was not stackable and produced such strange artifacts. My guess is that SGP, upon crashing, messed up with the camera settings and so the data taken after 2 AM was with some weird settings. Anyway, the image you will see below is without any darks, flats, or any other calibration frames.

Object Designation: M99 & M100

Also known as: N/A

Constellation: Coma Berenices

Object Type: Grand Design Spiral Galaxy

Distance: 45.2 & 55 million light-years away

Magnitude: 10.4 & 9.5

Discovered in: 1781

Messier 99 astrophotography with amateur equipment
Messier 99 from our full image

Messier 99 was one of the first galaxies discovered where the spiral pattern of the arms was confirmed. The pattern was noted by Lord Rosse in 1846, 65 years after Pierre Méchain discovered the galaxy.

M99 is very busy and contains many nebulae with tons of star formation areas within its arms. It is one of the most active galaxies in the Messier catalog.

M99 is similar in shape to Messier 87.

Messier 100 astrophotography with amateur equipment
Messier 100 from our full image

Messier 100 is one of the largest and brightest galaxies in the Virgo cluster.

Like the more famous M82 (the Cigar Galaxy), M100 is a starburst galaxy, meaning it creates new stars at an incredible rate. The most active star-forming region in M100 is within a ring of dust, close to the core of the galaxy.

Also, a total of seven supernovae have been found in M100 since the year 1901!

Below you can see our full image, once again, without any calibration frames! M99 can be seen in the bottom right, while the larger M100 is visible near the upper left. Other beautiful galaxies can be spotted all across the field of view.

Our image of M99 (bottom right) and M100 (top left).

Messier 99 and Messier 100 astrophotography


Camera: QHY600C

Telescope: Stellarvue SVX130

Mount: Astro-Physics Mach1

Accessories: Moonlite Nitecrawler focuser

Processing: Pixinsight


Total Exposure Time: 5 hours

Exposure Time per frame: 5 minutes

Filters: N/A

Gain: 26


How to Find M99 and M100?

How to find Messier 99 and Messier 100 in the night sky, constellation map

Messier 99 and Messier 100 can both be found close to each other in the constellation Coma Berenices. It can be difficult to know if you are looking at the right object because they are located in a field of dozens of galaxies!

Some of the bright members near M99 and M100 include:

... and more!

The easiest way to spot these two galaxies is to first locate the Virgo Cluster as a whole. Observing from a very dark site, like Bortle 2 or Bortle 1 will of course help. From the Virgo Cluster, slowly scan the area and drift towards the constellation Coma Berenices. You should be able to spot either M99 or M100 on your way there. Remember that M100 is slightly larger and brighter than M99!


Processing Messier 99 and M100

Processing M99 and M100 was a total nightmare. Not because these are difficult objects to process, but because our computer glitched during the night and our data could not be calibrated with any dark or flat frames.

M99 and M100 - Single 3 minute shot
M99 and M100 - Single 3 minute shot

See this mess below? This is what I had to deal with as a Master Light. Not only there is terrible vignetting and dust spots (flats would have fixed that), but there is also a considerable amount of noise (darks would have fixed that) and a rainbow artifact (nothing could have fixed that besides a perfect back focus which we still aren't able to achieve with the QHY600 and SVX130😅) The stars on the edges are also slightly elongated, which is related to the back focal distance as well.

The first thing I did was heavily crop the image so that the rainbow artifact was mostly gone and the vignetting was not visible. Then, I used StarNet to remove the stars and tried my best to even out the background using Lightroom. Back on PixInsight, I kept going through my usual processing workflow until being satisfied with the overall image and ended up on Lightroom once again to try to mask the dust spots.

M99 and M100 - Stacked master
M99 and M100 - Stacked Master

Use our step-by-step PixInsight Processing Workflow guide to process exactly as we do!


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Final Thoughts

Messier 99 and M100 are two small but beautiful galaxies. It is also nice to know that so many other objects can be captured at the same time when imaging either one of these galaxies. They are not difficult to process for beginners (assuming you don't have the same issues we did) and are pretty colorful!

Have you captured M99 and/or M100? Attach your image in the comments and let us know your acquisition details!

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Clear Skies,

Galactic Hunter


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