Hi, I'm new to bino viewing. Occasionally you see ads on astromart advertising "matched pairs" of eyepieces. Does this imply choosing 2 from a large set of samples that are the best match? Are manufacturing tolerances sufficient that just buying a pair of the same brand/type/fl is enough? Finally, do you try to buy them at the same time so you hopefully get them from the same manufacturing batch? I already have a large collection of eyepieces, would I be able to order one or two that match what I already have or is that not reccommended? I guess I don't know how much variation there is in precise focal lengths and how much that matters.
A lot depends on the manufacturer. I have never found a pair of Televue EPs of the same power and type that do not match. I have bought single Televue EPs at different times from different places without problems. My 21mm TV plossls are a good example. One has the lettering at the top of the EP, one has the lettering in the middle of the EP, they are still parfocal.
I have a pair of 2" 19mm and a pair of 2" 16.8mm Gary Russell EPs. The eyepieces were bought at different times from different people on Astromart. I had to put parfocal rings on them to make them easier to use.
All of my binoviewers have diopter adjustments but it is really a pain to have to equalize a set of eyepieces before you can use them.
I imagine if some manufacturer let tolerances slip or changed design, you could end up with eyepiece of slightly different power or FOV. These EPs could cause you to have problems, maybe even headaches when using them. Generally buying two EPs of the same type, from the same place, at the same time, will yield a closely matched set.
Burgess BV125 Model C Original 22mm BlackNights with Diopters and focal reducer 45mm Elite BlackNights with Diopters Sieberts 1.3X OCA, Sieberts UltraBarlow, Sieberts Multimag Denk IIs OCA. Denkmeier 2" SCT Star Diagonal (Modified) Denkmeier 2" Starsweeper SE Denkmeier 1 1/4" Starsweeper SE Stellarvue AT1010 Meade ETX90 Stellarvue 102APO Celestron C9.25 Orion Atlas 8" Meade 152ED
I'm new to this forum having just purchased a Baader Mark V binoviewer. A friend of mine had a Teleview binoviewer with click stop zoom eyepieces several years ago. He used them on his 12" Meade Lx200 and we tried them on my 15" Obsession. As I recall they worked fine. I was too busy trying to balance my scope to really give them a workout but the images merged easily and the eye relief is certainly comfortable. I have one that I use on a 5" celestron sct as a spotting scope setup and the only negative is the narrow FOV at the 24mm setting.
Just for fun I tried using two old Plossl's one an Orion 25 mm and one a Celestron 26 mm in my binoviewer. At focus the eyepieces weren't even quite at the same height. But much to my surprise it worked. I could merge the images - moon, stars, anything. It actually wasn't even that bad and better than mono. I in no way recommend using such a setup but it was an interesting experiment. If you get a chance try something like this sometime.
I think our brain is fairly adaptable in merging images - some people more than others. My guess is that any two samples of a particular eyepiece from any good manufacturer would likely work together just fine.