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Sh2-284 - Emission Nebula in Monoceros - Astrophotography

Updated: Mar 25

Sh2-284 is a colorful emission nebula in the constellation Monoceros. It does not have a nickname, but is often mistakenly called the Little Rosette Nebula (which is in fact Sh2-270). Because of that, why don't we call it the Portal Nebula? You can see why I decided to give it this nickname later in this post.

Sh2-284 is not often photographed, but is a good target for both beginner and experienced astrophotographers.

Object Designation: Sh2-284, LBN 983

Also Known As: The Portal Nebula (since today)

Constellation: Monoceros

Object Type: Emission Nebula

Distance: 15,000 light-years away

Magnitude: Unknown

Discovery: Unknown

In the northern hemisphere, the best time to photograph the Portal Nebula is in the Winter season.


Sh2-284 Astrophotography from a Dark Site

March 2024

Telescope at UDRO
Our telescope at UDRO

We photographed this target using our refractor telescope at Utah Desert Remote Observatories.

The Bortle 2 skies are fantastic, and you can inquire at UDRO if you'd like to have your scope next to ours!

The image below is the result of 30.5 hours in SHO. I rarely forget to spend an extra couple of hours shooting in RGB to get natural stars, but this time, I completely forgot! This is why the stars look white, magenta, and blue. I am overall happy with the picture, it shows the impressive nebula in the center with lots of wisps of gasses all around.

I have rotated the image in a way that was visually pleasing. Do you see the portal yet? If not, scroll down some more to see an explanation!

Click the image to see it in high resolution!

Sh2-284 astrophotography - The Portal Nebula in Monoceros


Camera: QHY600M  

Telescope: Stellarvue SVX130

Mount: 10Micron GM1000 HPS

Accessories: Moonlite Nitecrawler focuser / Pegasus Astro Ultimate Powerbox

Processing: Pixinsight with RC-Astro plugins, final touches in Skylum Luminar Neo


Total Exposure Time: 30.5 hours

Exposure Time per frame: 10 minutes

Gain: 56


How to Find Sh2-284

Map to find Sh2-284 in Monoceros

Sh2-284 can be found in Monoceros in the Winter sky. It is not far from the brightest star in the sky: Sirius, as well as Betelgeuse in Orion.

The constellation Monoceros was outlined by the Dutch globe maker Petrus Plancius in 1612. Along with Camelopardalis, Monoceros was only two of twelve proposed constellations to be approved by other astronomers during that year. The story is actually very interesting and you can learn all about it in The Constellations Handbook!

Sh2-284 can be seen from a dark site using a telescope or a pair of binoculars. It looks similar to the Rosette Nebula, but slightly fainter and much smaller.

You can find several other colorful deep sky objects not far from the Portal Nebula, such as:

The best time to observe and photograph Sh2-284 is in Winter.


Sh2-284 by NASA and ESO

NASA and ESO only photographed this target a few times, and none of the results are as impressive as what you'd see from the Hubble or the James Webb Space telescopes, but I'm sure they're probably very interesting scientifically speaking.

Sh2-284 by the VLT Survey Telescope - ESO
Sh2-284 by the VLT Survey Telescope - ESO

On June 7, 2023, ESO released the image you see here. It was taken with the VLT Survey Telescope from the Panaral Observatory.

The main goal of this was to capture the object in great detail, including the cluster of stars.

This cluster, visible near the center, is made up of young stars and is known as "Dolidze 25". It is emitting large amounts of radiation in all directions, as well as powerful stellar winds. This is the reason why the nebula seems to have a "hole" in its center.

NASA used the Wide-field Infrared Survey Explorer (WISE) back in 2011 to capture Sh2-284 in Infrared. The green and red colors you see represent the wavelength of infrared light.

Blue/Green shows the light emitted in 3.4 and 4.6 micron wavelengths. They mostly come from the stars.

Green/Red represent 12 and 22 micron light, which mostly comes from the dust.

Sh2-284 in Infrared - NASA
Sh2-284 in Infrared - NASA


Sh2-284 Nickname: The Portal Nebula

Why did I come up with the nickname "Portal Nebula"?

While doing research for this write-up about this nebula, I realized that several people call this "the Little Rosette Nebula". This is not true, as the Little Rosette Nebula is Sh2-270.

Just like the IFN vs ISM terms, we have to be careful not to blindly share false information online because it spreads quickly! If I did not already suspect the Little Rosette Nebula to be a different object, I could have also used that term in this blog after my research and contribute to spreading this sick, terrible, outrageous lie!

Why Sh2-284 is called the Portal Nebula
Little Stick Figures jumping into the Portal

Either way, this nebula does not have a name, so I decided to call it the Portal Nebula. Yes, I have no right to name this nebula, and it will never be official, but it looks like a portal to me in the orientation I ended up with, so I named it the Portal nebula.


Single Shot and Processing of Sh2-284

Below you can see what a the master files for each narrowband channels (H - S - O) looked like before being combined into one color image. As you can see, like it is the case for pretty much all emission nebulae, the Hydrogen Alpha channel is the one showing the most gas! It is followed by the OIII channel, and then the weakest of the three, the SII channel.

You can see the same type of comparison for many other targets on our Narrowband Expectation page.

Processing Sh2-284 was not too difficult but can be a bit tricky if you're trying to reveal as much of the fainter outer gas as possible. Make sure to not make the bright areas within the nebula too bright as you increase the visibility of the dimmer gas.

I had some gradients on my image, which I took care of with the GradientCorrection tool in PixInsight. After following my usual nebula processing workflow, I imported the image into Skylum Luminar Neo for some final touches.


Sh2-284 FAQ

  • In which constellation is Sh2-284 located?

You can find the Sh2-284 Nebula in the constellation Monoceros.

  • How big is Sh2-284?

The nebula has a diameter of 150 to 200 light-years.

  • How far is Sh2-284?

The Portal Nebula is located about 15,000 light-years away from Earth.

  • How long should my exposure times be when photographing Sh2-284?

We suggest doing 10-minute exposures for this object.

  • Should I use a filter to image Sh2-284?

Sh2-284 is a good narrowband target. As you saw in our comparison shots about the different channels, the H and O channels show a lot of signal. You probably could skip SII and do a bicolor HOO combination.


Sh2-284 Astrophotography - Final Thoughts

The Portal Nebula is a beautiful nebula in Monoceros. I love how colorful it looks, and that it is not too difficult to capture. Make sure to capture this object before the Winter season is over, although if you are a beginner, we suggest starting with the Rosette Nebula first.

Do you like the name "The Portal Nebula"? What would you have named it?

Make sure to follow us on Facebook, Instagram, and YouTube to stay up to date with our work!

Clear Skies,

Antoine & Dalia Grelin

Galactic Hunter



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