Fitting astronomy eyepieces to the little Nikon ED50


Senior Member
Sep 20, 2018
In someone's favorite spot
Some of you ED50 scope owners might find this useful or at the very least, interesting...

On the BirdForum, there is a thread started by a fellow named William Blunk who goes by Billb, about fitting regular astronomy eyepieces to the ED50 spotter. Bill is a former physics teacher, hobby scope maker and craftsman who used his knowledge and lathe to turn out some aluminum adapter rings that allowed him to fit standard 1.25" astronomy eyepieces to his ED50 (and presumably other Nikon ED Fieldscopes) spotter.

I got in touch with him a couple years ago after getting my ED50 with the standard Nikon 13-30 eyepiece. That eyepiece is good, but not great. I was intrigued by having the option to fit inexpensive fixed focal length wide angle astronomy eyepieces to the scope. He was kind enough to send me a couple of the adapter rings (last two he had, I think), and I quickly fitted his favorite eyepiece, the 20mm SWA to the scope. The resulting image was just amazing. Super wide field of view and impressive image quality for such an inexpensive eyepiece. Last year, I fitted a 15mm SWA eyepiece to use as my main backpacking spotter on elk and mule deer hunts. It worked very well too.

This year, I was curious about the higher quality astronomy eyepieces, so I bought a Pentax 12mm eyepiece to try. It was not the simple "plug and play" adaptation that the 15 and 20 SWA's were however. But after some cussing and elbow grease, I got it to work. And it's just fantastic. I'm really glad I made the effort now. That eyepiece will stay on my ED50 from here on out. The image quality is just incredible. The magnification isn't as high as I had hoped for (probably around 14-17x) but the wide field of view and extremely bright tack-sharp image more than make up for that. The eyepiece is also very robust and has a superb eyecup that can be rotated in our out. You're not going to find a better eyepiece for $125 that I know of.

Here's the longer write-up in the BirdForum thread if you're interested...



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