Explore Scientific Field Flattener for f/5 to f/7 Refractors

A field flattener is an optical corrector that compensates for the natural curvature of a refractor's focal plane. An f/6 refractor like the ED80 is fast enough to show noticeable star elongation (coma) in the corners of an image, especially with a larger sensor. The Explore Scientific Field Flattener is designed for the f/5 to f/7 range, making it a perfect match to ensure your astrophotos have sharp, pinpoint stars across the entire frame.

You must create a total distance of exactly 55mm between the flattener's rear flange and the ASI533MC Pro's sensor. The camera itself has a specific back focus distance (check its manual, often 6.5mm or 17.5mm depending on configuration). You will need to use a combination of threaded extension tubes (spacers) to make up the remaining distance to reach 55mm. For example, if your camera has 17.5mm of back focus, you would need 37.5mm of extensions.

No. This flattener is optically designed specifically for refractor telescopes in the f/5 to f/7 focal ratio range. Using it outside this designated range or with a different telescope design like a Newtonian will result in poor optical correction and unsatisfactory star shapes.

No, this is a photographic-only accessory. It is not designed to work with an eyepiece and will not allow you to reach focus for visual use. It must be threaded directly into an imaging train with a camera.

The most common cause of poor correction is incorrect back focus. The required 55mm distance has a very small tolerance of only +/- 2mm. Even a small error in your spacer calculations can degrade the result. Meticulously check the back focus of your camera and the length of all extensions in your imaging train to ensure the total distance is exactly 55mm.

No. This is a 1.0x field flattener, not a focal reducer. It is engineered to correct optical aberrations without altering the native focal length or focal ratio of your telescope.