How does the 0.8x reducer change the Askar 120APO's performance?
The reducer makes the Askar 120APO optically "faster," changing its focal ratio from f/7 to f/5.6. This reduces exposure times and provides a wider field of view by shortening the focal length to 672mm. It also functions as a field flattener, correcting for optical aberrations to keep stars sharp across the image.
What is the correct back focus for the Askar 120APO 0.8x Reducer?
The required back focus is a standard 55mm. This distance is measured from the base of the male M48x0.75 thread to your camera's sensor. This spacing is common for DSLR cameras with a T-ring or for dedicated astronomy cameras when combined with filter wheels and off-axis guiders.
Can I use 2-inch filters with the Askar 120APO 0.8x Reducer?
Yes. The reducer features a built-in female M48x0.75 thread on the telescope side of the M48 adapter, which is designed to accept standard 2-inch astronomy filters. This allows you to thread filters directly into the optical train for light pollution suppression or narrowband imaging.
Is the Askar 0.8x Reducer just a reducer or also a flattener?
It is both. While its primary function is to reduce the focal length, the triplet optical design is engineered to correct for field curvature, an aberration common in refractor telescopes. This ensures that stars are sharp not only in the center of your image but also at the corners.
Will this reducer allow me to image the entire Andromeda Galaxy (M31) with the Askar 120APO?
Yes, for most camera sensors. The reduced focal length of 672mm provides a much wider field of view than the native telescope. This makes it ideal for capturing large targets like the Andromeda Galaxy (M31) or the Heart and Soul Nebulae (IC 1805 and IC 1848) within a single frame.
If I'm imaging the Pleiades (M45) with the Askar 120APO, what's the main benefit of using this 0.8x reducer?
The main benefit is framing. The Pleiades (M45) is a large open star cluster, and at the native focal length of the 120APO, it can be difficult to fit the entire cluster and its surrounding nebulosity in the frame. The 672mm reduced focal length provides the wide field necessary to capture the cluster in its entirety, while the faster f/5.6 optics will better capture the faint, blue reflection nebulosity with shorter exposures.
