What is the main benefit of the Explore Scientific 3-inch Diagonal's 99% reflectivity?
The 99% reflectivity from its dielectric coating ensures maximum light transmission from your telescope to your eyepiece. This results in brighter images, which is especially important for viewing faint deep-sky objects like nebulae and galaxies, compared to standard diagonals which may only reflect 90-96% of the light.
Will the Explore Scientific 3-inch Diagonal fit my telescope?
This diagonal is designed specifically for telescopes equipped with a 3-inch focuser. It will not fit standard 1.25-inch or 2-inch focusers. It is most commonly used with large apochromatic refractors and Ritchey-Chrétien telescopes designed for wide-field imaging.
Why would I need a 3-inch diagonal instead of a 2-inch for my large refractor?
For a large refractor with a 3-inch or larger focuser, a 3-inch diagonal is critical for preventing vignetting (darkening at the edges of the field of view). This is most apparent when using full-frame imaging sensors or very long focal length, wide-field 2-inch eyepieces that utilize the entire light cone produced by the telescope.
How does the Explore Scientific 3-inch diagonal prevent damaging my eyepieces?
The included 2-inch adapter uses a brass compression ring to secure eyepieces. When you tighten the lock screw, the ring gently and evenly tightens around the eyepiece barrel. This provides a more secure grip than a single set screw and prevents the screw from digging into and scratching the barrel of your expensive eyepieces.
I'm imaging the Andromeda Galaxy (M31) with a full-frame sensor; will this 3-inch diagonal help?
Yes. Imaging a large target like the Andromeda Galaxy (M31) with a full-frame sensor is exactly the scenario where a 3-inch diagonal is most beneficial. It ensures the entire sensor is evenly illuminated by your telescope's light cone, preventing the vignetting that a smaller 2-inch diagonal would likely cause at the corners of your image.
Does the Explore Scientific 3-inch diagonal include an adapter for 1.25" eyepieces?
No, this diagonal comes standard with a 2-inch adapter only. A separate 2-inch to 1.25-inch adapter would be required to use 1.25-inch eyepieces, though this is not a typical use case for a diagonal of this size.
