Improve your astrophotography: mastering filters for nebulae
04 Dec. 2024
Astrophotography demands precision and the right tools to capture the breathtaking beauty of the night sky. Filters are essential for reducing light pollution and isolating specific wavelengths, allowing for clearer observations and stunning images of celestial objects like nebulae. Whether you’re battling urban light pollution or highlighting the unique characteristics of emission nebulae, mastering filters is key to enhancing your astrophotography.
Vaonis offers two expertly crafted filters: the CLS filter for light pollution reduction and the duo-band filter for advanced nebula imaging. Here’s everything you need to know to get started.
How astrophotography filters work
Light, colors, and wavelengths
Light is a combination of radiation of different wavelengths. When passed through a prism or rain droplets, it breaks into a spectrum of colors visible to the human eye.
For our eyes, different wavelengths manifest as the colors of the spectrum. The wavelength of visible light is measured in nanometers (abbreviation: nm, or one billionth of a meter). We can perceive wavelengths ranging from 380 nanometers, corresponding to the color violet, to 780 nanometers, corresponding to the color red.
The visible spectrum spans from the wavelengths 380 nm (violet light) to 780 nm (red light).
Smart telescope sensors detect an even broader range of wavelengths, including infrared, but filtering is often required to produce sharp images.
Celestial light vs. Artificial light
Celestial bodies and artificial sources emit light at varying intensities and wavelengths.
For instance, urban sodium vapor lamps emit strong yellow-orange tones.
Conversely, some deep-sky objects like emission nebulae ( such as The North America Nebula) radiate light at specific wavelengths, notably the hydrogen-alpha (656 nanometers, red light) and oxygen-III (500 nanometers, green light) lines.
Filters that block unwanted wavelengths and isolate these emission lines dramatically enhance contrast and clarity in astrophotography.
Vaonis filters: a perfect match for astrophotography
Broad-band filters: the CLS filter
Designed for versatility, broad-band filters like the Vaonis CLS filter reduce light pollution while preserving the visibility of most celestial objects. This filter transmits key wavelengths, including hydrogen-beta, oxygen-III, hydrogen-alpha, and sulfur-II, making it ideal for urban astrophotography.
They are an excellent entry-level choice for observing all types of nebulae. While other filters may be more effective at reducing light pollution, they are also more selective about the types of objects they allow you to observe.
The Vaonis CLS filter transmits parts of the spectrum near the hydrogen beta and oxygen III lines, with a 40-nanometer bandwidth, and the hydrogen alpha and sulfur II lines, with a 35-nanometer bandwidth.
Narrow-band filters: the duo-band filter
For more precise needs, the Vaonis duo-band filter isolates the hydrogen-alpha and oxygen-III emission lines with a narrow 12-nanometer bandwidth. This makes it particularly effective for observing emission nebulae whether in light-polluted urban environments or under dark skies as it reduces starlight and makes the nebula stand out, especially in dense star fields.
However, its selectivity limits its use to specific objects, such as emission nebulae, certain planetary nebulae, and supernova remnants. For experienced astrophotographers targeting high-contrast images, this filter is invaluable.
A simplified representation of the wavelength ranges filtered by the Vaonis Duo-Band filter.
Which filter should you use?
Depending on your target object and light pollution level, the choice of filter is crucial. Use the following table for guidance.
Light pollution levels are measured on the Bortle scale, ranging from 9 (extremely light-polluted skies of large cities) to 1 (a sky completely free of light pollution).
To determine the Bortle scale rating of your observation site, you can check the following map: https://www.lightpollutionmap.info
How to identify the type of nebulae
In the Singularity application, nebulae are identified and classified by type.
- Emission nebulae: These are well-suited for observation with the duo-band filter, particularly when located in star-rich regions. This makes them ideal targets for astrophotography.
- Reflection nebulae: These nebulae reflect the light of nearby bright stars and emit across a wide portion of the spectrum. They should not be observed with the duo-band filter, as it would excessively dim their overall brightness and color balance.
- Mixed nebulae: These combine both emission and reflection characteristics. It is also recommended not to use the duo-band filter for these nebulae, as it could excessively reduce visibility of certain parts of the nebulae.
Examples of nebulae to observe with the duo-band filter
In general, nebulae that are predominantly red or green are suitable for this filter. This includes numerous HII regions scattered throughout the Milky Way, which are often the focus of astrophotography.
Examples:
- North America Nebula
- Eagle Nebula
- Rosette Nebula
- Cygnus Loop (Veil Nebula)
- Pacman Nebula
- Tulip Nebula
- Heart and Soul Nebulae
- Bubble Nebula
- Crescent Nebula
- Tarantula Nebula
- Statue of Liberty Nebula
- Dumbbell Nebula (M27)
Examples of nebulae not recommended for the duo-band filter
Nebulae with blue, white, or yellow tones are generally not suitable for the duo-band filter.
Examples:
- Lagoon Nebula and Trifid Nebula (mixed)
- Orion Nebula (M42, mixed)
- Horsehead Nebula (mixed)
- Pleiades (reflection)
- Iris Nebula (reflection)
- Carina Nebula (mixed)
- Tarantula Nebula (mixed)
- Ghost of Cassiopeia (reflection)
- Helix Nebula
- Rho Ophiuchi (mixed)
About Planetary Nebulae
Certain planetary nebulae emit strongly around the oxygen-III emission line and can be observed with the duo-band filter. For example:
- Dumbbell Nebula (M27) is an excellent target for astrophotography using this filter.
However, other planetary nebulae emit across a broader spectrum and are better observed without the duo-band filter. For instance:
- Helix Nebula is better viewed unfiltered to capture its full range of light.
About Star Clusters
While star clusters may emit more intensely in specific visible spectrum colors (sometimes giving them a dominant hue), stars generally radiate across the entire spectrum. Using a filter, even to reduce light pollution, would dim their brightness.
Moreover, stars are highly contrasted against the sky, even in light-polluted areas. Therefore, filters are not necessary for observing star clusters, regardless of the sky quality.
About Galaxies
A galaxy contains a variety of celestial objects, primarily stars, and emits light across the entire spectrum. For this reason, it is not recommended to use filters when observing galaxies, except in environments with extreme light pollution.
This detailed guidance ensures that filters are used effectively, especially in astrophotography, to enhance specific celestial features while preserving natural light dynamics.
Join the enthusiasts
Products mentioned in the article
807 €
Enhance your astronomical observations with the Vaonis All-sky Filter Bundle, designed to optimize your stargazing experience in various conditions. This set includes three essential filters:
• Dual Band Filter: Perfect for astrophotography, this filter isolates specific wavelengths of light to enhance details in nebulae and other deep-sky objects.
• City Light Suppression Filter: Designed for urban skies, this filter reduces the effects of light pollution, allowing you to capture clearer and more vibrant celestial images.
• Solar Filter: Safely observe and photograph the Sun with this precision-crafted filter, revealing sunspots and solar activity.
Whether you’re observing from the city, the countryside, or during the day, this bundle equips you with the versatility to explore the skies in stunning detail.
What's in the box
- City Light Suppression filter
- Dual Band filter
- Solar filter
Selling Out Fast
628 €
Take your astrophotography to the next level with the Cosmic Filters Bundle, designed to enhance your celestial observations and photography. This set includes two premium filters tailored to optimize your Vespera experience, whether you’re observing under city lights or pristine dark skies.
1. CLS Filter (City Light Suppression)
The CLS filter is ideal for urban and suburban observations, effectively reducing the impact of light pollution. By attenuating artificial light, this filter increases contrast between celestial objects and the background sky, delivering clearer and more vibrant images. It’s the perfect tool for capturing the night sky from areas with significant light interference.
2. Dual Band Filter
The Dual Band filter is a high-performance narrowband interference filter that enhances the visibility of specific celestial phenomena. It precisely isolates the Hydrogen Alpha (H-alpha) and Oxygen III (O-III) wavelengths, commonly found in nebulae, allowing you to capture more defined stars and intricate details. Whether you’re observing from urban areas or natural environments, this filter significantly improves image quality, creating stunning, high-contrast astrophotography.
1 859 €
1 709 €
Embark on celestial adventures with the Vaonis Vespera smart telescope and its dedicated backpack, the Adventure Pack. Unleash your curiosity and explore the wonders of the universe with this versatile and portable bundle.
Whether you're a novice astronomer or an experienced stargazer, the Adventure Pack offers convenience and advanced technology for your cosmic journey.
Experience the thrill of discovery wherever your travels take you with the Vaonis Vespera and its specially designed backpack, the ultimate companion for your astronomical exploration.
What's in the box
399 €
The Vespera Dual Band Filter is a dual narrowband interference filter that will significantly improve your photo quality whether you are viewing from an urban or natural environment.
By selecting very precisely the wavelengths of Hydrogen Alpha (H-alpha) and Oxygen III (O-III), found mainly in nebulae, the filter will increase the contrast between the Stellar object and the sky background. Thus, its use makes it possible to obtain a higher-quality image, with sharper stars and finer details.
Keep only the essential
The Dual Band filter has been designed to allow only two particular wavelengths to pass through to the Vespera sensor:
- O-III
- H-alpha
Due to the filtered wavelengths, it is particularly effective for photographing nebulae in emission (e.g.: Orion nebula M42, Heart nebula IC 1805 …), dark nebulae endowed with hydrogen (e.g.: Horsehead or Elephant's Trunk nebula...), planetary nebulae (e.g.: Owl nebula M97, Dumbbell nebula M27...), supernova remnants (e.g.: Veil nebula, Crab Nebula M1...).
For globular clusters (e.g.: Hercules cluster M13, cluster M92...), the selectivity of the Dual Band filter will help you to obtain sharper stars.
A filter specifically studied for Vespera
The optical quality of the Dual Band filter has been specifically studied by our engineers to offer use at full aperture, without any impact on the optical diameter of the instrument. The lens ring is equipped with an electronic micro-card that allows Vespera to detect the Dual Band filter and adapt its observation and image processing parameters.
Transmission curve
The filter features 12nm of bandwidth in each wavelength (O-III = 500.7nm, H-alpha = 656.3nm).
In a nutshell
- Ideal for nebula photography
- Increases the contrast between the sky background and the stellar object
- Refines stars and details
229 €
The Vespera light pollution filter or CLS (City Light Suppression) filter allows you to improve the quality of your photos when observing in the city or suburbs. It attenuates the effects of light pollution and thus increases the contrast between the celestial object being photographed and the background sky.
The broadband filter blocks Na (sodium) and Hg (mercury) wavelengths mainly emitted by urban night lighting or undesirable natural light (atmospheric oxygen radiation, etc.), while allowing the main wavelengths from celestial objects.
The anti-light pollution filter is particularly useful for improving the brightness of deep sky objects: nebulae, star clusters, galaxies, etc. It is especially effective on emission nebulae because of the filtered wavelengths.
Examples of emission nebulae: Bubble (NGC 7635), Crescent (NGC 6888), Eagle (M16), Elephant’s Trunk (IC 1396), Flame (NGC 2024), Lagoon (M8), North America (NGC 7000), Omega (M17), Orion (M42), Pacman (NGC 281), Rosette (NGC 2237), Tarantula (NGC 2070), Thor's Helmet (NGC 2359), Trifid (M20), Tulip (Sh2-101).
Designed specifically for the Vespera lens, it fits easily and discreetly into the optical arm. The lens ring that holds the CLS filter is equipped with an electronic card that allows Vespera to detect it.
The filter is delivered in a transparent storage box.
3 427 €
3 277 €
Key Features and Technology
1. High-Resolution Imaging:
Vespera Pro leverages CovalENS technology, allowing image resolutions up to 50 megapixels, capturing intricate details of celestial objects like never before.
2. Precision Optics:
Equipped with a quadruplet apochromatic lens, Vespera Pro ensures sharp, vibrant, and color-accurate images by eliminating chromatic aberration.
3. Built-In Dew Sensor:
The integrated dew sensor automatically activates the dew heater, protecting the optics from moisture and ensuring uninterrupted sessions in varying conditions.
4. Enhanced Imaging Technology:
Exclusive to the Vespera Pro, BalENS technology dramatically improves image quality by enhancing weaker signals and reducing noise, ensuring clearer and smoother astrophotography. It also provides accurate color balance and a uniform sky background, making images more vivid and natural.
5. Expert Mode:
Elevate your astrophotography by customizing your field of view, framing, and camera settings. Capture calibration frames and retrieve 16-bit RAW files for advanced image processing with your preferred software.
