What is the correct back focus for the ES 3" 0.7x Reducer?
The required back focus is 55mm, measured from the rear flange of the reducer unit itself. The standard M42x0.75 T-thread adapter uses 3mm of this distance, leaving you with a 52mm spacing requirement between the adapter and your camera's sensor. This is a common distance for DSLR cameras with a standard T-ring.
Which Explore Scientific telescopes are compatible with this 3" 0.7x reducer?
This reducer/flattener is specifically recommended for the Explore Scientific 127mm and 152mm APO triplet refractors. It is not designed for use with their doublet refractors. It has been tested and confirmed to perform exceptionally well with optical systems at both f/8 and f/7.5.
Do I need a special adapter for my Explore Scientific 127mm APO refractor?
Yes, most likely. The ES 127mm APO refractor typically ships with a 2.5-hex focuser. To connect this 3" reducer, you must purchase the specific adapter, part number 510366. The reducer does include an adapter for the Explore Scientific 2-inch rack-and-pinion focuser, but this is not the standard focuser on the 127mm model.
How will the 0.7x reduction help when imaging the North American Nebula (NGC 7000)?
The 0.7x reduction provides a wider field of view, which is essential for framing large emission nebulae like the North American Nebula (NGC 7000) in their entirety, especially with larger sensors. It also makes your telescope faster (e.g., f/8 becomes f/5.6), significantly reducing the exposure time needed to capture the faint, expansive clouds of hydrogen-alpha gas.
What is the difference between a focal reducer and a field flattener?
This accessory combines both functions, but they solve different problems:
- A Focal Reducer shortens the effective focal length of your telescope. This makes the image brighter and the field of view wider.
- A Field Flattener corrects for the natural curvature of a refractor's focal plane, ensuring stars are sharp and round across the entire image, not just in the center.
Can I use the Explore Scientific 3" reducer for visual observing?
This device is designed and optimized specifically for astrophotography. Its optical corrections are calculated to produce a flat field on a camera sensor at a precise 55mm distance. It is not intended for visual use with an eyepiece and will not perform as a standard visual accessory.
