There are three open clusters in the constellation of Auriga. Messier 37, or M37, is the largest, brightest, and most populated of the three. M37 is also known as the Salt and Pepper cluster but in my eyes, it looks more like a pair of underwear in space.
Object Designation: M37, NGC 2099
Also known as: The Salt and Pepper Cluster
Object Type: Open Cluster
Distance: 4,511 light-years away
Discovery: Giovanni Battista Hodierna before 1654
This object is great for beginner astrophotography because it's a quick and easy object to photograph. The cluster is very simple and it does not require many hours of exposure to obtain great results. It is best photographed in the Winter season. I have imaged M37 several times so I'll show you our results below and how best to photograph it with astrophotography tips.
M37 and its Hidden Nebula from a Dark Site
Re-shooting M37 has been on my To-Do list for a long time, and I finally decided to do it in March of 2023! I used our 655mm refractor that is hosted under the Bortle 2 skies of Utah Desert Remote Observatories and chose to shoot three hours of data with our monochrome camera. I did 1 hour on each R, G, and B filter until I thought it was enough for this target.
Before I combined the data, I decided to spend some time shooting this cluster again but this time with the Hydrogen Alpha filter, and so spent an extra 10 hours on it just for HA.
I actually had no idea that a nebula was hiding inside the cluster, and originally just shot that extra Ha data just for fun... and I'm glad I did!
Telescope: Stellarvue SVX130
Mount: 10Micron GM1000 HPS
Guiding: ZWO ASI 290MM Mini
Accessories: Moonlite Nitecrawler focuser / Pegasus Astro Ultimate Powerbox
Processing: Pixinsight, with RC-Astro plugins
Total Exposure Time: 13 hours
Exposure Time per frame: 1 minute for RGB, 10 minutes for Ha
Filters: Chroma 3nm R/G/B/H
M37 with an Unmodified DSLR and Reflector Telescope
This was my very first attempt at imaging the M37 cluster and was done from a Bortle 4 zone.
The photo below was captured in just 45 minutes, doing 3-minute exposures with our DSLR camera at ISO 800. What we wrote about it back then was that while it wasn't the most grandiose object in the sky, it was still a beautiful cluster of stars to capture.
Had we used a modified DSLR camera at that time or spent more time on it, we would have likely been able to reveal the faint nebula within the cluster. It also would have made us the first amateur astrophotographers to capture it... Oh well 😢.
Camera: Canon 7D Mark II
Telescope: 8" Newtonian
Mount: Motorized Equatorial Mount
Guiding: Autoguider - 50mm Guide Scope
Total Exposure Time: 45 minutes
Exposure Time per frame: 3 minutes
15 lights - 15 Darks - 15 Bias
How to Locate Messier 37
M37, or Messier 37, lies 4,500 light-years away in the constellation of Auriga, between Gemini and Perseus. It has an angular size of 24 arc-minutes and a real size of about 25 light-years across.
To find it, first locate the sixth brightest star in the night sky: Capella. The open cluster is on the opposite side of that star towards Gemini, just to the exterior of Auriga’s pentagon asterism. Unlike M37, both M36 and M38 are inside the pentagon shape.
Messier 37 can not be resolved with the naked eye, but its brightest stars can easily be seen through binoculars assuming you are observing from a dark site. A small telescope might reveal about 20 bright stars, while bigger instruments will reveal hundreds of stars, including the fainter members.
The Planetary Nebula in M37
Given the designation "IPHASX J055226.2+323724", this small planetary nebula is mostly made up of Hydrogen Alpha (Ha), with some Oxygen III (OIII) as well. It is believed to be the oldest planetary nebula ever found in the universe, with an age of 70,000 to 80,000 years old.
The object is just the third planetary nebula ever found in an open cluster as of 2023! It's mindblowing knowing that we were a few months from being the first ones to take a picture of it, but hopefully, we get a second chance with a different discovery!
Truthfully it is a beautiful object. It is very small and has an interesting S-shape with bright red Ha color. The fact that it is seen just behind the bright stars of the cluster also makes it unique and cool!
Scientists were able to determine that the gas in the nebula is expanding at a speed of 20 kilometers per second (12 miles) using Spectra. You can go through all the research on this planetary nebula by reading the official essay article.
Processing Messier 37
Processing M37 was very easy and fun. The tricky part was, of course, to reveal the faint nebula within the cluster which is rich in hydrogen alpha. The way we processed it was by removing the stars and using several different processes to bring out the colors and details in the nebula. That's our astrophotography tip to you so that you can get the most out of your image. Other nebulous gasses can be seen around the objects, and those were naturally revealed at the same time as the small planetary nebula.
Below you can see what each channel looked like before being combined. Hover over each of the images to see each channel name. Being a cluster, each filter does look the same but you'll notice that only the Ha filter (bottom right) shows a hint of faint nebulosity behind the stars.
Astrophotography Tips for Processing Images
If you would like to learn how I process all of our images, you can access our comprehensive guide. Find information on the guide here.
The First Picture Ever Taken of Messier 37
Who was the first to photograph M37, and when?
The first ever picture of the M37 cluster was taken on February 8th, 1893 by Isaac Roberts. This is 130 years before our image!
Roberts used a 20" reflector telescope and his total integration time was 90 minutes. Below you can see a comparison shot between Isaac Roberts' image and ours.