The Saturn Nebula

2021-10-31 NGC 7009 Saturn Planetary Nebula

Planetary Nebula NGC 7009

Caldwell 55

Apparent magnitude8.0
Apparent dimensions41″ × 35″
Image exposure:
51 Minutes
Image field of view:
5 x 5 arcmin (estimated)
Image date:

This is a beautiful and unique planetary nebula, estimated to be roughly 3000 light years away. It consists of an intricate web of gas emissions* from the 11th magnitude central star, as it transformed from a low mass main sequence star into the hot (55,000 K) white dwarf it is today.

*This paper by Walsh et al (table 3) indicates that hydrogen helium, nitrogen, oxygen, sulfur and chlorine are the abundant elements in NGC 7009 (not that I have any expertise in reading scientific papers).

This object has nothing to do with Saturn or any other planet.

It is called a planetary nebula because back in the early days of telescope astronomy it was noticed that such objects were not point-like stars but had a discernible diameter, just like planets do. They didn’t know what they were but unfortunately the name has stuck – as have the names of many of the objects discovered in the infancy of modern astronomy.

It was called the Saturn Nebula because in over-exposed images, like the one below, it has a Saturn-like appearance which is not detected in images intended to record the structure of the main nebula. When I look at the above image from the side of the screen, I can see the ghostly shape of faint green nebulosity surrounding it which hints at its name. I don’t know if all screens will do this.

Over-exposed image of NGC 7009
from the Simbad Data Base

This was the first test night for my new configuration and my first night back on the front driveway after the ending of our three months covid confinement. I expected some hiccups but they turned out to be very minor and user-centric. 🥴

My Meade LX-90 telescope on EQ6R-Pro mount.

More planetary nebulae to come…..

Cosmic Focus Observatory

34° S

Above us only sky….

Telescope:Meade LX-90 2000mm focal length, 203 mm dia
Optics:Astronomik light pollution filter.
Mount & Guiding:SkyWatcher EQ6-R Pro mount.
Imaging camera:ZWO ASI 071 MC cooled.

Images © Roger Powell
I’m one of the founder members of Macarthur Astronomical Society

Do it!


  1. Your new equipment setup seems to have performed well. I wish I could be there in person to see it and watch what you do. It would be very interesting.

    Liked by 1 person

    1. Most of the object names in astronomy are a legacy from the eighteenth and nineteenth century. Sometimes it can be fun trying to see the shape they saw in their pioneering telescopes.

      Liked by 1 person

Leave a comment or ask a question . . . .

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s