Sigma ART lens focusing solution

Posted on Tuesday, February 11, 2025 by RICHARD HARRIS, Executive Editor

Do you own a Sigma ART 85mm lens and need a reliable focus solution? The Nightfall Ring Platform is custom-designed for the Sigma ART 85mm F1.4, providing a seamless, fully integrated imaging setup. This precision mounting system securely accommodates essential gear, including a ZWO Electronic Auto Focuser (EAF), guidescope, filter wheel, ASIAIR or miniPC, power distribution unit, and even a piggyback camera with the optional ballhead adapter plate.

The Sigma ART 85mm F1.4 lens has become a favorite among astrophotographers due to its fast optics and wide field of view. Compared to a Rokinon 135mm, it offers nearly twice the sky coverage, making it an excellent choice for capturing large deep-sky objects and widefield compositions. One of the more impressive examples is the Integrated Flux Nebula (IFN) region, where galaxies M81 and M82 stand out against the delicate wisps of interstellar dust. The combination of this lens and a well-integrated mounting system like the Nightfall Ring Platform makes capturing such images more efficient and reliable.

Focusing has always been one of the most challenging aspects of astrophotography. The fast optics of an F1.4 lens create a razor-thin critical focus range, making precise adjustments crucial. A manual approach is often inconsistent and frustrating, especially as temperature changes throughout the night. By integrating a ZWO EAF focuser with the Nightfall Ring Platform, astrophotographers can achieve repeatable, precise focusing without manual intervention. The backlash-free belt system allows for fine control, ensuring the image remains sharp from dusk until dawn.

One of the biggest advantages of using the Nightfall Ring Platform is the ability to set up a fully automated imaging system. The combination of a ZWO EAF, a guidescope, and an ASIAIR or miniPC allows for complete remote operation. This means astrophotographers can control their imaging session from anywhere in the world. Whether it's capturing the Milky Way from a remote desert in Chile, imaging southern sky objects in Namibia, or setting up a remote observatory in the U.S., this platform makes it possible to acquire high-quality images without being physically present at the telescope.

Nightfall Ring Platform for Sigma ART lens, 85mm F1.4 specifications

The Nightfall Ring Platform is designed and manufactured in the USA using 3D-printed components made from PETG and PLA+ (tough). These materials are resistant to water and can withstand extreme temperatures ranging from -15F to 175F. All hardware included in the kit is made of 18-8 stainless steel, and the anodized red aluminum thumbscrews provide secure attachment and easy adjustments.

85mm Focuser Animation


The Nightfall Ring Platform is compatible with the following lens:

  • Sigma ART 85mm F1.4 for Canon or Nikon
     

What's Included in the Standard Mounting Kit:

  • Two (2) heavy-duty mounting rings
  • Vixen accessory saddle rail
  • Two (2) anodized red thumbscrews for accessory saddle
  • Two (2) anodized red thumbscrews for mounting rings
  • Miscellaneous 18-8 stainless steel mounting screws
  • Two (2) M6 socket screws for mounting rings to a dovetail bar
     

What's Included in the ZWO EAF Mounting Kit:

  • Everything in the standard mounting kit
  • Focus gear assembly
  • Timing belt
  • Timing pulley
  • ZWO EAF mounting bracket with stainless steel mounting screw
     

The Nightfall Ring Platform provides a reliable and convenient way to assemble a professional-grade astrophotography system. Whether used for local imaging sessions or integrated into a remote observatory, it allows for a seamless experience, minimizing the need for manual adjustments while maximizing imaging efficiency. For astrophotographers looking to get the most out of their Sigma ART 85mm F1.4 lens, this platform offers a structured and well-designed solution to streamline the imaging process.

Fully automated system


A fully integrated mounting platform for use with a Sigma ART 85mm F1.4 lens for widefield astrophotography


Sigma ART 85mm F1.4 lens specifications

  • Lens Construction: 19 elements in 15 groups (3 FLD, 1 SLD, 4 aspherical)
  • Angle of View: 114.2°
  • Number of Diaphragm Blades: 11 (rounded)
  • Maximum Aperture: F1.4
  • Minimum Aperture: F16
  • Minimum Focusing Distance: 30cm / 11.9 in.
  • Filter Size: Rear filters only
  • Maximum Magnification: 1:11.9
  • Weight: L-Mount: 1170g / 41.3 oz. | Sony E: 1160g / 40.9 oz.
  • Dimensions (Diameter x Length): L-Mount: 101.4 x 149.9mm / 4.0 x 5.9 in. | Sony E: 101.4 x 151.9mm / 4.0 x 6.0 in.
     

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