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The D131F1200 is a double-separated, multi-layer green film objective lens built for telescope makers who want a true upgrade in optical performance without buying a whole new scope. With a 131mm caliber and 1200mm focal length, this objective is sized for serious light-gathering and detailed views of planets, lunar craters, and deep-sky targets, making it a strong centerpiece for a DIY or replacement telescope build.

What sets this objective apart is its two-element, air-spaced design. Rather than a single cemented lens, the lens group uses two separate elements with a precise 0.2mm spacer between them — included free with purchase. This spacing is critical: without it, image quality drops noticeably, with increased chromatic aberration and softer focus. The multi-layer green film coating further reduces reflections and improves light transmission, helping deliver sharper, higher-contrast images with better color accuracy, especially useful when observing high-contrast targets like the moon’s terminator line or planetary bands.

Who Is This For?

This objective lens is best suited for telescope hobbyists, DIY astronomy builders, and anyone restoring or upgrading a refractor telescope who understands basic optical assembly. It’s not a plug-and-play consumer product — it’s a precision component for someone building or repairing a scope who wants observatory-grade light gathering and glass quality rather than a cheap stock lens. If you’re comfortable handling optical elements and assembling a telescope’s optical tube, this is a meaningful upgrade path. Casual stargazers looking for a ready-to-use telescope should look elsewhere, as this is strictly the objective lens assembly.

Bottom Line

The D131F1200 Double Separated Multi-Layer Green Film Objective is a thoughtfully engineered optical component for telescope builders who care about image quality. The 131mm caliber and 1200mm focal length give it strong resolving power, while the two-element air-spaced design with the included 0.2mm spacer and green film coating work together to minimize aberration and maximize clarity. For DIY telescope enthusiasts seeking a precision objective lens to build around, this is a solid, purpose-built choice.

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  • Product Name: D131F1200 Double Separated Multi-Layer Green Film Objective
  • Caliber: 131mm; Focal length: 1200mm
  • This Objective Is A Double Separated Multi-Layer Green Film
  • The objective lens group is composed of 2 separate lenses, and a special spacer of 0.2mm thickness is placed in the middle (no spacer will seriously affect the image quality), and the spacer is free upon purchase.
  • Package Include : 1Pcs
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