Description

Astro-Tech AT66EDQR 0.8 Reducer for the AT66EDQ

The AT66EDQs most useful quality for imaging isnt something that shows up prominently in the specs: it produces a genuinely flat field across a full-frame sensor without a separate field flattener. Most refractors even good ones need that extra element. The AT66EDQ doesnt. The AT66EDQR reducer preserves that optical behavior while doing two things that matter for wide-field imaging: it shortens the focal length from 462mm to 370mm and brightens the system from f/7 to f/5.6.

At 370mm f/5.6, the AT66EDQ becomes a serious wide-field imaging platform. The Orion Nebula complex fits comfortably in a single frame. The Pleiades with surrounding nebulosity. The large emission nebulae in Cygnus the Veil, the North America, the Pelican which become cramped at longer focal lengths. And at f/5.6, an exposure that would take 8 minutes at f/7 finishes in about 5. On a night with limited time or variable transparency, thats a meaningful difference.

The camera side of the reducer uses standard 48mm T-threads, connecting to a T-ring for DSLR and mirrorless bodies, or directly to dedicated CMOS and CCD astronomy cameras, which come with 48mm T-threads built in. Back focus from the reducer shoulder to the image plane is 55mm the industry-standard spacing, so theres no guesswork in your camera positioning. A soft rubber cap covers the T-threads when not in use; a second cap protects the scope-side barrel.

This reducer is designed for the AT66EDQ specifically. It works with the quadruplets optical geometry to maintain flat-field performance across the full sensor. It is not interchangeable with other AT refractors.

Whats in the Box

• Astro-Tech AT66EDQR 0.8 focal reducer
• Camera-side rubber dust cap
• Scope-side rubber dust cap

Features

• 0.8 reduction focal length 462mm 370mm; f/ratio f/7 f/5.6; approximately 36% shorter exposures for equivalent signal
• Flat-field performance preserved designed specifically for the AT66EDQ quadruplet; sharp stars to the corners of full-frame sensors
• Fully multi-coated optics maximum light transmission; no additional flare or scatter introduced into the optical path
• 48mm T-thread camera connection DSLR and mirrorless bodies connect via a T-ring (sold separately); dedicated CMOS/CCD astronomy cameras attach directly 48mm T-threads are standard on most
• 55mm back focus industry-standard spacing from reducer shoulder to image plane; no guesswork required
• AT66EDQ-specific design matched to the quadruplets geometry; not compatible with other AT refractors

Frequently Asked Questions

What camera bodies work with this reducer? DSLR and mirrorless cameras connect via a T-ring for your specific mount (sold separately) available for Canon EF, Nikon F, Sony E, Fuji X, and most others. Dedicated CMOS and CCD astronomy cameras typically have 48mm T-threads built in and connect directly without a T-ring.

Do I need anything else to connect my camera? You need a T-ring for your camera mount (sold separately). The T-ring threads onto the reducer’s 48mm T-thread and attaches to your camera body. No other adapters are required.

Do dedicated astronomy cameras need a T-ring? Yes, with the appropriate T-ring for your mirrorless mount (sold separately). Dedicated CMOS and CCD astronomy cameras attach directly no T-ring needed. In all cases, back focus from the reducer to the image plane is 55mm confirm this works with your cameras flange-to-sensor distance.

Can I use this reducer with other AT refractors? No. The AT66EDQR is designed specifically for the optical geometry of the AT66EDQ quadruplet. Using it with other scopes will not maintain flat-field performance and may produce poor corner stars.

Tech Details: