Mis à jour : 28 avr. 2020
The Rosette Nebula is one of the largest, most beautiful and also most popular target for amateur astrophotographers. Yet, it took us 4+ years before attempting it ourselves.
Tonight, I will be heading to a Bortle 2 zone and use a very fast Newtonian reflector telescope to image this "flower" in space.
We'll talk about the telescope more in depth later in this post, but you can see what the beast looks like on the right!
Lucky for us, the telescope came with an Optec focuser! We had never used electronic focusers before, but we now had a reason to learn how to!
We have a video about our attempt at the Rosette Nebula with the Takahashi E-180 on our YouTube channel. Check it out!
Here is our image of the Rosette Nebula, 3 hours in total taken from a Bortle 2 zone.
NGC 2244 using the Takahashi E-180 and the ZWO ASI 1600MM
Camera: ZWO ASI 1600MM
Telescope: Takahashi Epsilon-180
Guiding: ZWO ASI 290MM Mini
Acquisition: ZWO ASIAIR
Total Exposure Time: 3 hours
Exposure Time per frame: 3 minutes
How to find the Rosette Nebula?
The Rosette Nebula is located in the constellation of the unicorn: Monoceros. It is also pretty close to the brightest star in the night sky, Sirius!
Using binoculars or any telescope, one can easily spot the cluster of stars in the center of the nebula. Because the gases are mostly Hydrogen Alpha, it can be difficult to observe this object without a filter. The best way to find it visually is to use a small instrument and to of course be under a very dark site.
Discovered in 5 different parts over time
Also called “The Skull”
It is one of the most massive emission nebulae in the sky
Processing of the Rosette Nebula
The processing part was not difficult but very annoying. The Takahashi E-180 telescopes are famous for being very well built and to hold collimation for any months. Sadly, our loaner seemed to have lost its collimation either before or during the shipping.
As you can see on the Hydrogen-Alpha frame below, the bottom left corner of the image shows elongated stars. Although it is not such a major issue, it still affects a part of the image that is too large to be cropped out.
We do not have the required collimation tools and, to be honest, patience to fix this issue knowing we have a limited time available with this telescope. We tried to collimate the secondary mirror for several days (thanks Jorge for your help!) and feel like we managed to correctly do it, but the images show some tilt, which is probably due to the primary mirror. Sadly, we do not feel comfortable taking the mirror out and decided to return the telescope after a couple of weeks.
What did each narrowband channel look like?
Below you can see what one hour of total exposure on each channel revealed. We used three filters to capture the Rosette Nebula:
Hydrogen Alpha (left)
Sulfur II (center)
Oxygen III (right)
The Hydrogen Alpha is obviously the one that shows the most data!
You can get our full PixInsight workflow as a PDF "follow along" file HERE.
The telescope used: Takahashi Epsilon-180 f/2.8
Let's talk a bit more about the telescope we used to get this image of the Rosette Nebula.
As we explained many times, our first telescope in our astrophotography journey was the Orion 8" Astrograph f/3.9. A very fast and affordable Newtonian reflector telescope which we reviewed on both our website and YouTube channel.
The Takahashi E-180 is also a fast Newtonian reflector telescope, well, it is a Hyperbolic Newtonian. With a speed of f/2.8, the Epsilon 180 is noticeably faster than our first telescope, meaning we can capture more in less time.
It has a focal length of 500mm, which is perfect for capturing nebulae of medium to large sizes as well as clusters and large galaxies.
Optical Design: Hyperbolic Newtonian
Aperture: 178mm (7")
Focal Ratio: f/2.8
Image Circle: 44mm
Limiting Stellar Magnitude: 14
Tube Length: 19.7"
Tube Diameter: 232mm
Tube Weight: 22 lbs.
Our video about trying out this telescope for the first time
If you'd like to learn more about how I imaged the Rosette Nebula with this telescope, you can watch the video below!
Although I am sad about the collimation issue, I am glad I had the chance to image with such a wonderful telescope. I hope to one day own a Takahashi product as the craftmanshi in these telescopes is absolutely top-notch.
I'm not very satisfied with this final image of the Rosette Nebula. I believe I should have spent more time with the Sulfur II filter in order to bring out more crisp details. I was unable to spend more than three hours on it as it went below the horizon pretty quickly.
Have you captured the Rosette Nebula? Attach your image in the comments and let us know what you used!
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