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LE Eyepieces

Started by markvcostello3, 08/02/2003 04:01AM
Posted 08/02/2003 04:01AM Opening Post
Good evening:

I'm looking around for a couple of eyepieces to go with a telescope I'm waiting for and am considering the so-called "long eye relief" or LE eyepieces. I personally might not need them as I wear glasses for nearsightedness. However, I'm guessing they might be advantageous to have especially if my wife and/or kids are also out with me. We wouldn't have to keep changing the focus every time we took turns.

I consider myself a newbie, having been out of the hobby for several years. In particular, I don't know that much about LE eyepieces. I was hoping y'all could help with the following questions.

1) The big advantage of LE eyepiece is eye relief long enough for people who wear glasses. Do these eyepieces have disadvantages? If yes, what are they?

2) For those of you who wear glasses for nearsightedness or farsightedness, would you have an LE eyepiece in your scope for sessions with other people looking through your scope (e.g., you and your kids, star parties, etc.)?

Thanks for your response(s).

Mark Costello
Matthews, NC, USA

"I hear you're mechanically inclined. Did you ever do anything with perpetual motion?"

"Yeah, I nearly had it a couple of times."
Posted 08/02/2003 04:43AM #1
I've never used one, but the 7.5mm and 5mm and probably the shorter focal lengths only have 9mm of eye relief. I don't think that is long enough for eye glasses. For not much more you could pick up TV Radians or Pentax ep's. Even less if you can find them used here.

For your second question, 9mm is very comfortable eye relief for non glasses wearers.Unless you have astigmatism you should be able to focus an ep without your glasses although anybody looking in the ep after you would have to refocus.
Hope that helped,
Posted 08/02/2003 05:30PM #2

Are you speaking specifically of Takahashi's LE series or about eyepieces with long eye relief in general? Tak's LE series is so-named for having longer than normal eye relief, but not generally enough for eyeglass wearers in shorter focal lengths. Tele Vue Radians, Pentax XLs (and now XWs), Vixen LV and LVWs, and a host of cheaper chinese imports now sport eye relief long enough for eyeglass wearers, even in short focal lengths. One disadvantage is the scatter you get from the extra glass elements. Another is that some effort is often required to get comfortable with the eyepiece to view without accidental blackouts from moving the eye out of position. Another disadvantage is a greater liklihood of external reflections aka eye glint. This is where the bright light of a planet bounces off your eye, back to the large eye lens, and then back to your eye again as reflection that moves quickly with your every move. Advantages are, of course, the comfort of eye relief, relative freedom from fogging, and generally better edge correction in faster scopes. I mainly use eyepieces with long eye relief. I have a 7mm Tak ortho and a 6mm TMB SuperMono to frequently test whether I'm missing anything. I haven't had the TMB long enough to say, but nothing so far has convinced me that the benefits of less glass outweigh the benefits of viewing comfort and enjoyment that I get with my eyepieces having longer eye relief and wider apparent fields of view.