A pair of 3X, 1.25" E.S. barlows, or "focal extenders', as they are called by the manufacturer, arrived in the mail today. Just had to conduct a quick test after the Montana Grizzly football game was over, in spite of biting winds, darkish, cloudy conditions, and snow coming over the eastern horizon.
The extenders were tried on my APM 150 and 100 ED binoculars.
These extenders have the standard E.S. cuts in the tubes, supposedly to keep them from falling out of the focusers. I had a little trouble getting them to seat and tighten properly in the 2" to 1.25" eyepiece adapters, and the adapters to tighten up properly in the big focusers. Maybe because of the sudden cooler temperatures?
I also usually had to rotate and fiddle with the eyepiece location in the barlows to get good image merging. I always could do it with enough fiddling, though.
All of the eyepieces that I tried came to focus with travel to spare in both the APM 150 and the 100 ED binoculars. These were Morpheus 17.5's, and 6.5's, Pentax XL14's, Docter 12.5's, and E.S. 4.7's.
Image quality was expectedly not great in the 4.7's and 6.5's, but not that bad considering they were providing just short of 550X and about 388X in the big 150, respectively.
The lower powered eyepieces were much better with generally clear, sharp views. I would say that image quality rivaled that of the original eyepiece without the extender, although no direct comparisons were made.
There was a problem getting close to a full field view in the Pentax XL14's, until I discovered that I had the adjustable eyecups screwed all of the way down. A quick rough adjustment of eyecup height pretty much solved that problem, although it seemed that eye placement was still somewhat critical with these.
The same was true of the E.S. 4.7's, but at that power, I'm not surprised.
It became evident that eye placement and consequently inter-ocular adjustment of the bino was more critical when using the extenders, especially at higher powers.
I believe these extenders will be very useful in both of my APM bino's, when higher powered views are needed.
I was greatly relieved to see that all eyepieces tried easily came to focus.
Can't wait for this storm to clear so I can try them out on the night sky!
Edited by oldmanrick, 28 September 2019 - 08:49 PM.