Looking to upgrade your standard 25/26mm eyepiece? Look no further than the Astro-Tech 25mm PF series eyepiece.
So, I know someone will wonder what exactly PF stands for. It isn't just some letter choosen at random for reasons unknown. They actually stand for Premium Flat Field.
This Astro-Tech 25mm PF eyepiece is an excellent medium to low power eyepiece for all types of observing in all types of seeing conditions. As long as you aren't out observing in a blizzard or downpour, you should be good. This 25mm should be a noticable step up from the 25/26mm eyepiece that comes with most scopes as standard equipment. Their physical size and flat field would also make them excellent choices for a binoviewer.
With a short focal length refractor it is a low power eyepiece. With the 430mm focal length Astro-Tech AT72EDII, for example, its four lens/three group multicoated glass optics provide 17x and a field that is nearly seven times as wide as the full Moon. This is well suited for scanning the crowded star clouds of Sagittarius, encompassing globular clusters, getting lost in the faint details of emission and reflection nebulas among other things. This series of eyepiece is designed to have an inherently flat field, so it will excell at wide field observation.
It functions so well for medium magnification observing with long focal length refractors, reflectors, or catadioptric scopes. On an 8" f/10 catadioptric, for example, it yields 80x. You can get lost inside clusters or just gazing at the moon for hours on end.
The four lens/three group design of the 25mm Astro-Tech PF provides all of the optical virtues described at the top of this catalog page - high contrast, a sharp and flat field from edge to edge, excellent color fidelity, and exceptionally low astigmatism and barrel distortion. It has a usable eye relief of 23mm, which is just excellent for all observers. The eyepiece some with a traditional rubber fold down eye cup to assist that glasses wearers of the world find a comfortable eye position. This particular eyepiece has a nice 65° apparent field of view, which is a tad wider than the 5.5 and 10.5 PF.
Enjoy the night skies with this very reasonably priced premium eyepiece.
