Optimal Focal Length for Astrophotography (Info)
In the captivating world of astrophotography, the choice of focal length plays a crucial role in capturing the vastness of the cosmos. The preferred focal lengths vary depending on the subject, whether it's the Milky Way, deep space objects, or planets.
For Milky Way astrophotography, wide-angle lenses are the preferred choice to capture the expansive Milky Way and some landscape. Common focal lengths range from 14 mm to 24 mm, with 24 mm often considered a sweet spot that balances landscape and Milky Way detail well. Wider options like 16 mm can capture more of the sky but with less detail; going up to 24 mm enhances detail while still fitting the Milky Way well in the frame. Fast apertures (around f/2.8 or wider) are important due to low light conditions. Typical settings also include shutter speeds of 15-25 seconds and ISO 1600-3200 to gather ample light without excessive noise.
Deep space astrophotography requires more magnification to capture faint nebulae, galaxies, and star clusters. Focal lengths usually range from about 50 mm up to 200 mm or more. A star tracker is essential due to longer exposures to avoid star trails. A lens around 70-200 mm f/2.8 is popular for deep sky imaging as it offers a good trade-off between field of view and resolution. Lower focal lengths help beginners as the tracking alignment demands are less strict.
Planetary astrophotography demands much higher magnification to capture fine surface details. Focal lengths need to be very long, typically in the order of 1000 mm and above, often achieved with telescopes or telephoto lenses rather than standard camera lenses. The Takahashi FSQ-106ED, an apochromatic refractor, is a popular choice for deep sky imaging due to its relatively small focal length and aperture compared to other big telescopes, and its substantially cheaper price than the Planewave CDK models and the ASA 20.
In summary, 14-24 mm lenses are best for Milky Way images, 50-200 mm lenses or zooms with tracking for deep sky astrophotography, and very long focal lengths achieved with telescopes for planetary astrophotography. A 24mm lens combined with a full-frame sensor camera is wide enough for Milky Way photography and can yield spectacular results. For planetary imaging with a telescope, a long focal length is desired for high magnification and a narrow field of view. However, longer focal length is not necessarily better, as it will have a narrow field of view which may not be ideal for deep sky astrophotography. Long focal length telescopes, like Celestron's Schmidt-Cassegrain range, are the most popular choice for planetary imaging.
Anthony Robinson, the founder and owner of Skies & Scopes, a publication and community focused on amateur astronomy and astrophotography, is a renowned figure in the field. His work has been featured in various publications such as Amateur Astrophotography, Forbes, the Guardian, DIY Photography, PetaPixel, and Digital Camera World.
| Astrophotography Type | Common Focal Length Range | Notes | |-----------------------|----------------------------------|-------------------------------------| | Milky Way | 14 mm – 24 mm | Wide angle, fast lens (f/2.8 or wider)| | Deep Space | 50 mm – 200 mm (and up) | Requires star tracker and good aperture| | Planetary | 1000 mm and above (telescope use) | High magnification critical for detail |
- In the realm of Milky Way astrophotography, focal lengths ranging from 14 mm to 24 mm are preferred, with a 24 mm lens being a sweet spot that provides a good balance between landscape and Milky Way detail.
- Deep space astrophotography calls for focal lengths from about 50 mm up to 200 mm or more, and a star tracker is essential due to longer exposures to avoid star trails.
- Planetary astrophotography requires extremely long focal lengths, typically in the order of 1000 mm and above, often achieved with telescopes or telephoto lenses.
- A lens around 70-200 mm f/2.8 is popular for deep sky imaging as it offers a good trade-off between field of view and resolution.
- Long focal length telescopes, such as Celestron's Schmidt-Cassegrain range, are the most popular choice for planetary imaging, offering high magnification for capturing fine surface details.
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