If there were a place to call heaven in space, this would be it. This magnificent, blue reflection nebula has a bright young star in its center and gradually becomes darker as it is surrounded by clouds of interstellar dust.
NGC 7023 itself is bright, but it is surrounded by very faint dust. It is a gorgeous object located in the northern constellation of Cepheus. The Iris Nebula is a difficult target for beginner astrophotographers, and will test your processing skills to the max!
Object Designation: NGC 7023, Caldwell 4
Also known as: The Iris Nebula
Object Type: Nebula
Distance: 1,300 light-years away
Discovery: October 18, 1794 by William Herschel
We have imaged the Iris Nebula several times and will show you our attempts below. The three main tips we can give you if you plan on photographing the Iris Nebula are to escape light pollution as much as possible, take very long exposures, and practice processing faint interstellar dust.
Iris Nebula Wide-Field Astrophotography with the QHY600C Camera
August 2022, Bortle 2
In late August 2022, I decided to spend two full nights on the Iris Nebula from a dark site.
My main goal was to get as much IFN (Integrated Flux Nebula, or space dust) in the area around the Iris Nebula. I decided to shoot it using a small refractor telescope and a full-frame camera.
The combination of the two gave me a wide field of view and allowed me to include a lot of things around the object itself.
You can see the setup used on the left. The mount was obviously overkill for this lightweight rig, but this was a few days before finally receiving the ZWO AM5!
I made a video about capturing the Iris Nebula from a dark site. It was a great night but full of bugs attempting to kill me. It was also my first time using NINA for astrophotography!
I am overall pleased with the image. Bringing out so much of the IFN meant sacrificing some of the quality and multiplying the noise, but I really wanted to see as much dust as possible.
Our image of the Iris Nebula showing the amount of dust all around. Click for High-resolution.
Telescope: Radian 75
Guiding: ZWO ASI 290MM Mini
Accessories: Pegasus Astro Pocket Powerbox
Power: Jackery Lithium Battery
Processing: Pixinsight, with RC-Astro plugins
Total Exposure Time: 15 hours
Exposure Time per frame: 10 minutes
Iris Nebula Astrophotography with a Reflector Telescope and Full-Frame Camera
April 2020, Bortle 2
First light with our first full-frame camera!
The Iris Nebula has always been one of our favorite deep sky objects, but we never were able to get a good-enough image of it to be proud.
The Iris Nebula region is pretty faint and cannot be imaged in narrowband, so you will need to escape light pollution in order to photograph it. On top of that, interstellar dust is very difficult to work with and requires special editing techniques. As you can see below, the image is full of such dust.
The fact that the central star is so bright and that the nebula itself has an enormous amount of details does not help either. If you feel like you have the dark skies and the processing skills needed for this wonderful nebula, go ahead and capture it, but be ready to spend several hours processing it.
Here is our image of the Iris Nebula, 4.5 hours in total taken from a Bortle 2 zone.
NGC 7023 using the QHY128C
Telescope: 8" Astrograph
Mount: Orion Atlas EQ-G
Guiding: ZWO ASI 290MM Mini
Total Exposure Time: 4.5 hours
Exposure Time per frame: 5 minutes
How to find the Iris Nebula in the Sky?
The Iris nebula can be found 1,300 light-years away in the constellation Cepheus.
The best time to image the Iris Nebula is in the Summer, but it stays available in the sky all year long for many regions in the northern hemisphere. You will need to travel far from the city and evade light pollution if you wish to get the best possible view of NGC 7023.
If you are having trouble finding the constellation Cepheus, first locate the North star, Polaris. The constellation we need is the one just to the south of Polaris, not far from Cassiopeia.
To locate the nebula itself, look for the bright star Alderamin, and simply go north until reaching another bright star (Alfirk). NGC 7023 will be a little bit to the southeast.
The Iris Nebula is not visible to the naked eye, even from a dark site. Spotting the object with binoculars is a nearly impossible task. A 10”+ telescope will reveal some faint nebulosity, as well as its bright central star.
Iris Nebula Information
The Iris Nebula has the designation NGC 7023, but is also known as Caldwell 4. NGC 7023 technically refers to the cluster of stars visible inside the nebulous gases of the Iris. The designation for the full-size nebula is LBN 487.
Being a reflection nebula means that the gases are illuminated by the stars within. In this case, most of the light comes from the bright central star, SAO 19158 which has a magnitude of 7.4.
The Iris Nebula is made up of "petals", making the object look like a blue flower in space. It spans 6 light-years across, and is surrounded by dark interstellar dust also known as IFN (Integrated Flux Nebula).
The image above was taken by NASA using the Hubble Space Telescope. It shows a very small portion of the Iris Nebula (3.3 arcminutes) where you can see some beautiful gases interacting. The picture appears reddish because it is a composite of four exposures using blue, green, near-infrared and H-alpha filters.
This specific part of the nebula is lit up by a bright star just above the frame, HD 200775. This star is about ten times the mass of our Sun.
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