As we bid farewell to summer, I welcome Fall. As I become more familiar with astro-imaging, I thought it would be a great time to tackle my first project – This is my first completed image with the three most common narrowband filters: SII, OIII, and Ha. The object has a large output of emission nebulae in Cygnus.
About the Project
NGC 7000 (The North American Nebula) with IC5070 (Pelican Nebula) in Narrowband- Total of 6 hours and 40 minutes. I have always wanted to shoot these objects, and I did back in August and I failed horribly; I struggled with poor framing; which led to composition issues and guiding issues, which resulted in star trails; all rookie mistakes. “Each mistake is an opportunity to learn. Failure only comes from giving up. What matters is the courage to continue.” A quote from Chris Bradford, The Way of the Sword.
This object is quite large, it would require a very widefield approach or two scopes. A perfect time to test the two-scope approach. I also decided to image using narrowband filters. Narrowband imaging is classified as, using filters to isolate and capture specific wavelengths of light through them. Deep-sky astrophotography enthusiasts can produce dynamic images of objects in space through their telescope with the help of narrowband filters.
Narrowband filters capture a small part of the visual spectrum. Narrowband filters are narrow to pass a very restricted band of wavelengths around specific emission lines of Ha (Hydrogen Alpha), Hb (Hydrogen Beta), SII (Sulphur), and OIII (Oxygen).
- Ha (Hα) 656nm
- Hb (Hβ) 486nm
- S-II 672nm
- O-III 496nm
Two Narrowband single frames
About the Objects
The North America Nebula NGC 7000 (Caldwell 20) and the nearby Pelican Nebula, (IC 5070) are parts of the same interstellar cloud of ionized hydrogen (H II region). Between the Earth and the nebula complex lies a band of interstellar dust that absorbs the light of stars and nebulae behind it, and thereby determines the shape as we see it. The distance of the nebula complex is not precisely known, nor is the star responsible for ionizing the hydrogen so that it emits light. If the star inducing the ionization is Deneb, as some sources say, the nebula complex would be about 1800 light-years distance, and its absolute size (6° apparent diameter in the sky) would be 100 light years. The North American Nebula is often mistakenly referred to as the “North American Nebula”. The remarkable shape of the nebula resembles that of the continent of North America, complete with a prominent Gulf of Mexico. This emission nebula lies near Deneb in the tail of Cygnus. It is 2° by 12/3° across, or 10 times the area of the Full Moon.
Although it covers an area more than four times the size of the full moon, its low surface brightness makes it difficult to observe with the naked eye. However, under sufficiently dark skies, you can see it as a foggy patch of light through binoculars or telescopes with large fields of view (approximately 3°).
It was first discovered on 24th October 1786, by William Herschel discovered it, but it was cataloged by his son, John. They both saw the shape as indistinct, combined with abundant stars in the Milky Way. German astronomer Max Wolf photographed the area in 1890 and named it the North America Nebula. NGC 7000 is part of a larger complex — Sharpless 2–117 — that includes the Pelican Nebula (IC 5070) and the swath of dark dust that separates the two, named L935 by Beverly Lynds in 1962.
Edwin Hubble proposed that the hot, luminous star Deneb was responsible for ionizing the North America Nebula’s gas, making it glow. However, at a mere 14,840 degrees Fahrenheit (8,230 degrees Celsius), Deneb is not hot enough. It’s also too far from the nebula. Instead, the nebula’s real energy source — the star J205551.3+435225 — is five times hotter than Deneb. It lies between the North America and Pelican nebulae, embedded within L935. That dark nebula dims the spectral type O3.5 star by 9.6 magnitudes; it would otherwise be one of the brightest stars in Cygnus.
For Northern Hemisphere observers, Cygnus lies in the bright patch of Milky Way visible in the late summer and autumn skies. Within that, the North America Nebula is bright enough that, in theory, it could be seen with the naked eye under perfect skies. With very good conditions, the right binoculars will show it as a large, amorphous glow 3° east of Deneb. In a 4- or 6-inch rich-field telescope with a wide-field eyepiece, the nebula fills the field of view. The Atlantic Coast and Florida are its most distinct features, thanks to their contrast with the adjacent dark nebula. Mexico is less conspicuous and the West Coast blends into the rich Milky Way star field. UHC filters really bring out the nebula, while reducing the glare from the foreground stars.
Observing Details
RA center: 20h 58m 15s.19 DEC center: +44°19′28″.50
Location in the Sky
Annotated Image
About the Imaging Location
Broemmelsiek Park was made possible by the commitment of Jack and Betty Broemmelsiek to preserve the natural beauty of St Charles County. The original land acquisition of Broemmelsiek Park took place in July 2002, which included a partial donation from the Jack Broemmelsiek family. Located about 6 miles South of Wentzville, Broemmelsiek Park is a St. Charles County Park with a dedicated astronomy site that is open 24/7.
The park is split into three main areas: A main park, an off-leash dog area, and an astronomy view area.
Every Friday night, weather permitting, the Astronomical Society of Easter Missouri (ASEM) members conduct an open house during which most of the telescopes there plus many portable telescopes are used for public viewing. It is a great family event.
The Bortle Scale Class sky for this area is about 5.
Equipment used
Scopes: RedCat 51, with the ASI2600 and Askar FRA400 with the ASI6200
Acquisition details
Between both scopes the filters and image frames were: Antlia ALP-T Dual Band 5nm 2″: 40×300″(3h 20′) (gain: 100.00) -10°C bin 1×1 and Antlia ALP-T Dualband 5nm SII&Hb 2″: 40×300″(3h 20′) (gain: 100.00) -10°C bin 1×1.
Integration: 6h 40′ Lights 80, Darks 40, Flats 40, and Flat darks 40. Avg. Moon age: 22.07 days Avg., Moon phase: 50.78%Bortle, and Dark-Sky Scale:5 .00
Moon Phase: Last Quarter, Moon age: 21.02 days, Moon illumination: 53.09%, Moon tilt: -18.152°, Moon angle: 0.5, Moon distance: 396,537.51 km and Moon sign: Cancer.
Fun fact: if you live in the Northern Hemisphere, the left side of the moon will be illuminated during the Last Quarter. If you live in the Southern Hemisphere, the right side is illuminated.
Software Used
Pleiades Astrophoto PixInsight · Russell Croman Astrophotography BlurXTerminator · Russell Croman Astrophotography NoiseXTerminator · Russell Croman Astrophotography StarXTerminator.
The Final Images
Until the next adventure and thank you for stopping by!
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You replied to this comment.
Steve my friend, I so appreciate you doing this. It means more than you know.
Very cool pics! I will check them out when i have a few minutes!
Thank you so much.
A fantastic project, Miguel. That’s a very well done write up and I learned a few things.
Obviously I’m not very knowledgeable using the narrow band filters. Is it possible to create a composite of both to represent all the different wavelengths in one image? This would, in theory, give a result that might be more comparable to a traditional “RGB” image?
Ah, maybe that’s what the first image in the series at the bottom represents?
Thank you for reading my post. The merged file of the Ha/OIII and Hb/SII. Is the last image on the post. Please let me know if It is not visible
OK, I can see it now. It wasn’t there before for me.
It’s likely an upload error. Let me know your thoughts.