Astro-Tech 0.8x reducer/field flattener for f/6 refractors


Availability: More on the way

This economical Astro-Tech 2" 0.8x reducer/field flattener is designed for astrophotography with f/6 focal ratio refractors, but will also work well with refractors in the f/5.5 to f/7 range . . .
Our Product #: ATR8
Astro-Tech Product #: ATR8

Product Description

New for August 2021, thread on adapter tops to choose between 42mm T-threads and 48mm T-threads.

While this Astro-Tech #ATR8 0.8X reducer/field flattener is designed for prime focus astrophotography with quality f/6 focal ratio apo refractors such as the Astro-Tech AT72ED and AT130 apo, it will also work well with Astro-Tech and other brand refractors in the f/5.5 to f/7 range that use a 2" focuser.

For example, the fully-multicoated Astro-Tech ATR8 converts the 430mm focal length f/6 Astro-Tech AT72ED refractor into a 344mm f/4.8 lens for faster and wider field astronomical and terrestrial photography, while the 777mm f/7 Astro-Tech AT111EDT converts into a 622mm f/5.6.

In addition to reducing the focal length of the telescope and thereby increasing the photographic speed, the ATR8 flattens the normal field curvature inherent in all refractors to provide images that are sharply focused out to the very corners of a large format DSLR chip. Stars look sharp and point-like all the way across the field in your images. You don't have to worry about photos that are sharp in the center and blurry at the edges.

The Astro-Tech ATR8 reducer/flattener fits 2" focusers. The 2" telescope-side barrel is threaded for standard 2" filters and has a beveled safety groove. The camera side of the reducer has an adapter choice beteen 42mm T-threads, or 48mm T-threads, to connect to a T-ring and camera body. A thread-on metal cover protects the T-threads when the reducer is not in use, while a slip-on dust cover is provided for the 2" scope-side barrel. Back focus is 55mm from the shoulder of the reducer to the image plane, the standard spacing for 35mm and DSLR camera bodies. The image circle at the focal plane is 42mm in diameter.

Tech Details

Weight 5.6 oz.
Warranty 1 year


Review by:
Yes, I moved into the world of wider angle AP with a SW 72ED (thanks, Astronomics!) and an ASI533. There was a small bit of coma at the edges as expected, and this FF gave nice round stars across the FOV. Included as an extra bonus, the 0.8X reducer aspect enables many of the larger nebulae to fully fit into the image FOV. The spacers included with the ASI533 and the configuration recommended by ZWO worked perfectly with the ATR8. The ATR8 manufacturing and optical quality is outstanding with a perfect fit in both the focuser and camera spacers.

This product is a must-buy for the shorter FL refractors! (Posted on 2/18/2021)
Review by:
I purchased this reducer to be used with the earlier version AT72ED. As with any refractor, the stars at the center are nicely focused, but the farther you get away from the center, the bigger the stars appear. This accessory eliminates that problem and gives a flat field all the way to the edge of an APS-C imaging chip. The reducer feature allows me to image large objects such as the North America Nebula in its entirety. (Posted on 10/23/2019)
Review by:
I use the Astro-Tech 0.8x reducer/field flattener for f/6 refractors when I am imaging with the Astro-Tech AT72EDII Refractor OTA FPL-53 f/6. Without this reducer/field flattener, the images that I am taking look like a fisheye effect. But when I am imaging with this on, its a flat image from the middle to the outside. (Posted on 1/13/2019)
Review by:
I use this reducer with my Explore Scientific 102mm FCD-100 APO and it gives me a flat field all the way to the edge, even in the corners on both my ASI1600MM-Pro and my Canon 1200D (APS-C chip). Very happy with this reducer! (Posted on 10/23/2018)
Review by:
I use this field flattener/reducer on my AT72, William Optics 98FLT, and Celestron 80mm Onyx. Works great in the F/6 - F/6.25 range on these telescopes using a ZWO ASI071 pro OSC with the APS-C size sensor. Provides sharp stars to the edge of the field. (Posted on 10/14/2018)
Review by:
An absolute must have accessory for the AT-72 if you are into photography (day or night) or Electronic Assisted Astronomy (aka video astronomy). Helps reach focus more easily and the extra photographic speed is appreciated, as is the flatter field. (Posted on 10/8/2018)
Review by:
(Posted on 8/4/2017)
Review by:
I bought this ff/fr to use on an Explore Scientific AR152 with a Canon 400d camera. It worked perfectly well for me, yielding the promised larger field of view, better light gathering (20% faster imaging system), and improved star shapes in the corners of the field (though they weren't too bad to begin with. I only stopped using this because I moved to a monochrome imager + filter wheel, and it didn't have the proper back-spacing. (Posted on 8/4/2017)
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