Skip to Content

NGC 7635 – The Bubble Nebula

The Bubble Nebula was an astrophotography project I will not soon forget.  In the fall of 2016, I spent almost 2 months straight capturing data on NGC 7635 from my backyard.

Bubble Nebula

NGC 7635 – The Bubble Nebula

The Bubble Nebula is an H II region emission nebula in the constellation Cassiopeia.  It lies very close to a star cluster known as Messier 52, as seen in the image above.  Through a large telescope under dark skies, the Bubble Nebula appears as an extremely faint shell around the central star.  I certainly can not visually observe NGC 7635 from the backyard!

The photo above is a wide-field view of the area, as seen through my Explore Scientific ED102 F/7 refractor.

HaRGB Composite

The photo above is a composite image of the Bubble Nebula photographed in both RGB and Ha.  The RGB version of the image simply means it was photographed in regular full color with a DSLR Camera.  The Ha (Hydrogen Alpha) was captured using a clip-in narrowband filter Ha filter in the camera.  By combining the RGB and H-Alpha images together, more detail can be presented.

Canon EOS Ha Filter


The filter I use is the Astronomik 12nm Ha Filter for Canon EOS cameras.  It clips into my camera easily with no extra adapters needed.

This filter blocks out almost all sources of light other than a narrow wavelength of Hydrogen Alpha.  Because of this, I am able to capture images during the full moon, and through heavy light pollution.


The Bubble Nebula in H-Alpha:

Bubble Nebula in Ha

Astrophotography from the backyard

This object is quite difficult to capture from a light polluted backyard!  The Bubble nebula is extremely faint and requires many hours of exposures to pull forward. Even with the additional Ha data, the HaRGB version was a little disappointing to me after so many hours of work.

RGB Photo Details

Total Exposure: 7 hours, 42 minutes (150 frames)
Photographed on Sept 15, Oct 3, Oct 7, Oct 8 2016

View the astrophotography equipment used for this image

Ha Photo Details

Total Exposure: 2 hours, 8 minutes (32 frames)
Photographed on Oct 31, 2016

I learned a lot about capturing Ha Data and combining it with RGB through this project.  The toughest part of the process is finding the right balance between the 2 versions.  Too much Ha – and you lose the natural color of the nebula.  Too much RGB – and you are leaving out significant detail in the object.  The method I used to combine the Ha and RGB data is outlined in this article from Starizona:

Using and H-Alpha Image as a Luminance Channel

Astrophotography Tutorial: Processing H-Alpha with a DSLR

If you are interested in the techniques used to process the Ha portion of the image above, watch the following tutorial video:

View more astrophotography tutorials.