Astrophotography Filter Guide: Exploring the Best Filters for Capturing Stars and Galaxies


Astrophotography is a captivating and technically demanding pursuit requiring specialised equipment and knowledge to capture the awe-inspiring beauty of the night sky. Central to this art form are filters which are designed to enhance the quality of astrophotography images. 

Whether you are aiming to capture distant galaxies, the intricate details of nebulae or the brilliance of stars, selecting the right astrophotography filter is crucial. 

Choosing the appropriate filter has the potential to revolutionise one's astrophotography journey entirely. However, the sheer variety of astrophotography filters available in the market often leads to a bewildering array of choices. ND filters? Light pollution filter? Or perhaps the best CPL filter? Delving into this maze, this blog seeks to shed light on some of the most exceptional filters tailor-made for the world of astrophotography.

The Need for Astrophotography Filter in Photography

Astrophotography is a pursuit that demands precision, patience and an unwavering commitment to detail. Filters serve several pivotal purposes, making them essential for those with a passion for capturing the breathtaking beauty of stars, planets and deep-sky objects. Here are a few reasons why astrophotography filter is not just a useful addition but an absolute necessity for any photographer who aspires to delve into the cosmos; 

1. Minimising Light Pollution:

In urban and suburban areas, artificial light sources can significantly hinder an astrophotographer's ability to capture celestial objects with clarity.  An astrophotography filter effectively reduces the impact of light pollution and enhances the visibility of distant objects.

2. Enhancing Contrast and Detail:

Astrophotography filters play a crucial role in enhancing the contrast and detail of celestial objects. Few filters are designed to isolate specific emission lines from nebulae and galaxies. By doing so, they enable astrophotographers to capture fine details and structures that might otherwise be lost in the overwhelming brightness of the night sky.

3. Isolating Specific Features:

Different astrophotography filters are tailored to isolate specific features of celestial objects, allowing photographers to focus on particular aspects of the night sky. 

4. Flexibility and Artistic Expression:

Astrophotography filters also offer photographers a degree of creative freedom. They can be used to experiment with various artistic effects from enhancing the colours of nebulae to creating unique and visually stunning compositions. Filters open up possibilities for photographers to express their creative visions in the cosmos.

Various Types of Filters for Astrophotography 

1. Astrophotography filter 

The Astrophotography filter R640 is a specialised optical filter designed to enhance the imaging of astronomical objects particularly those emitting specific wavelengths of light in the red part of the spectrum. This filter is designed to isolate and boost the transmission of 640 nm wavelengths, which is associated with hydrogen-alpha (Ha) emission, a common feature in many nebulae and other celestial objects. 

By isolating this specific wavelength, the astrophotography filter R640 helps astrophotographers capture stunning images of hydrogen-rich nebulae with enhanced contrast and detail. It is particularly effective in reducing the effects of light pollution and increasing the visibility of faint nebular structures, making it an invaluable tool for astrophotographers seeking to reveal the hidden beauty of the cosmos in their images.

The astrophotography filter R640 was created under the supervision of Dr. Akio Nakanishi in response to the demands of passionate astrophotography enthusiasts. It has entered the market despite being discontinued by leading manufacturers due to limited sales volume, primarily because it caters to the preferences of astrophotography enthusiasts.

2. CPL filter

While CPL (Circular Polarizer) filters are primarily employed to reduce reflections and enhance sky contrast in photography, they are not common in astrophotography. Yet, some astrophotographers experiment with the best applications of a CPL filter for unique applications. One valuable use is reducing the Moon's glare, especially when capturing lunar details or eclipses. Additionally, the best CPL filters can minimise reflections within telescope optics, enhancing image contrast when photographing bright celestial objects like planets. They can also help control sky background brightness for better composition in wide-field astrophotography.

3. Drone Filter Photography

Drone filter photography, often referred to as drone camera filter photography, is a specialised approach to aerial photography that involves attaching filters to the camera lens of a drone to achieve specific photographic effects or enhance image quality.

In astrophotography, the night sky serves as the canvas and the primary focus is on capturing stars, planets, galaxies and other celestial phenomena. Drone filter photography is used to capture time-lapse sequences of celestial events or to provide a unique perspective of astronomical phenomena. 

4. Dual GND Filter

dual GND filter is a distinct filter widely used in astrophotography. A dual GND filter allows precise exposure control by combining two graduated ND filters into one. With varying densities in each section, a dual GND filter balances exposure when capturing celestial objects against bright skies. The darker part reduces sky exposure while the lighter section maintains landscape detail. Moreover, the dual GND filter effectively combats light pollution by blocking artificial light on the horizon and enhancing celestial object clarity in night skies.

5. Light Pollution Filter

A light pollution filter, a crucial tool in astrophotography, serves the purpose of mitigating the detrimental impact of artificial light on night sky images. It accomplishes this by selectively blocking specific wavelengths of light that are often associated with urban and suburban light pollution, including the distinct yellow or orange hues from sodium and mercury vapour lamps. 

By allowing natural starlight and the emission lines of celestial objects to pass through, the light pollution filter significantly enhances image contrast, improves the visibility of faint celestial details and preserves the accurate colour balance of astronomical objects. The light pollution filter is particularly invaluable when photographing from locations with substantial artificial lighting as the light pollution filter helps astrophotographers capture clear and detailed images of stars, galaxies and nebulae while minimising the disruptive effects of light pollution.

In conclusion, the world of astrophotography is illuminated by a variety of specialised filters, each playing a pivotal role in capturing the mesmerising beauty of the cosmos. These filters, from the revolutionary Astrophotography filter R640 to the light pollution filter, offer astrophotographers the means to overcome challenges posed by the natural and artificial environment. With these filters in their arsenal, astrophotographers can transform ordinary nights into extraordinary visions, capturing the splendour of stars, galaxies and nebulae in unparalleled clarity and artistry.