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  1. #1
    Chris Jewell's Avatar
    Chris Jewell Guest

    Default Which eyepieces for a fast newtonian?

    For a new Newtonian (f/4.5 primary, about f/5.2 with a Visual
    Paracorr), I'm planning to get 4 eyepieces, which need about 20mm eye
    relief for my eyeglasses, and good correction for the fast light cone.
    The scope will be driven, so I don't need extremely wide fields. The
    candidates so far are:

    ~ 5.5mm exit pupil:
    Pentax XL30W XW (or older version if available used)
    Siebert Ultra Plus 30mm on 2-inch barrel
    Televue Panoptic 27mm

    ~ 4mm e.p.:
    Pentax XL20W XW (or XL21 if available used)
    Siebert Ultra Plus 22.5mm

    ~ 3mm e.p.:
    Pentax XL14W XW (or XL14 if available used)
    Siebert Ultra 15mm
    Televue Radian 14mm

    ~ 2mm e.p.:
    Pentax XL10W XW (or XL10.5 if available used)
    Siebert Ultra 11mm
    Televue Radian 10mm

    My questions for the group are:

    1. Are there other eyepieces with comparable eye relief and
    correction which I should consider?

    2. Has anyone done side-by-side comparisons of the similar-focal-
    length eyepiece groups listed above?

    In particular, how well do Siebert's Ultra (Plus) e.p.'s do against
    the more-expensive Televue and even-more-expensive Pentax e.p.'s in
    sharpness (center and edge), contrast, astigmatism, brightness,
    ghosting, or other attributes that I haven't thought to mention?

    I don't mind paying good money for high quality, but I don't object to
    a bargain either, especially if it comes with the satisfaction of
    doing business with a domestic small business/craftsman, too. I don't
    recall encountering any Siebert eyepieces at my local star parties, so
    I'm interested in what experience SAA folk have with them. Are they
    only "good for the price", or are they quite simply "good"?

    OBTW, my observing interests are mostly deep sky.

    Thank you.

    Chris Jewell San Jose CA, USA

  2. #2
    Stephen Paul's Avatar
    Stephen Paul Guest

    Default Which eyepieces for a fast newtonian?

    "Chris Jewell" <> wrote in message


    The XW seem to blackout as you back away and move to the side. That doesn't
    work for me since I do that all the time. Blackouts aren't as much of a
    problem if you are seated and the eyepiece position is always comfortable,
    but if your Newtonian focuser gets into some funky positions (and without
    rotating tube rings it will) then the critical eye position might become a
    secondary issue (and nusance).

    The Radians, XL's and Panoptics seem to be better in this regard than the

    Personally, although you don't mention them, I really like the Nagler T6s at
    13mm, 9mm and 7mm in my 80mm F5, 125mm F10, 200mm F10/F6.3, and 250mm F5
    telescopes. These allow a backed away position and only blackout going the
    other way; if you get in too close to the eye lens. I also have 35mm and
    24mm Panoptics at the low power end. The eye relief is too short on all but
    the 35mm for comfortable use with my eyeglasses, which correct for
    astigmatism with large exit pupils (only) on bright objects (like M45). If
    you don't need your glasses to correct astigmatism at small exit pupils, the
    Nag T6's ($280) are really nice eyepieces. Even if you keep your glasses on
    and don't use the entire field of view. They are surprisingly small and

    Try before you buy.
    -Stephen Paul

  3. #3
    mikeS's Avatar
    mikeS Guest

    Default Which eyepieces for a fast newtonian?


    See Chris, this goof wants you to go out and rob a bank to finance the likes
    of $250 EP's
    This is the crux of the problem with elitist a'holes that profess EP's that
    cost as much as a
    Chiny made telescope. When you ask questions like that, you are always
    going to get these clowns on SAA

    Just get yourself standard Celestron or Meade EP's and you will do fine
    unless you have money to burn.

  4. #4
    Del Johnson's Avatar
    Del Johnson Guest

    Default Which eyepieces for a fast newtonian?

    My votes are for the 21mm and 14mm Pentax XL (old style). These are my
    favorites and I have tried quite a few. The 27mm Panoptic is also excellent
    if you don't mind the pincushion distortion. My primary criteria is that
    the eypiece should offer an "easy view", that is, one should enjoy the view
    without having have to be thinking about eye position and blackouts.

    Del Johnson

    "Chris Jewell" <> wrote in message
    Jose CA, USA

  5. #5
    Stephen Paul's Avatar
    Stephen Paul Guest

    Default Which eyepieces for a fast newtonian?

    "mikeS" <> wrote in message


    Nagler T6 are cheaper than Pentax XW.

  6. #6
    Lawrence Sayre's Avatar
    Lawrence Sayre Guest

    Default Which eyepieces for a fast newtonian?

    On Tue, 17 Feb 2004 19:13:17 GMT, Stephen Paul <>

    Not if you buy the XW's through "Adorama". Just click where it says
    "Transaction Price" to see what they will actually sell them to you for.
    Amazingly lower prices than list.

    Lawrence Sayre
    My philosophy, in essence, is the concept of man as
    a moral being, with his own happiness as the moral
    purpose of his life, with productive achievement as
    his noblest activity, and reason as his only absolute.

    Ayn Rand (in the appendix to 'Atlas Shrugged')

  7. #7
    Stephen Paul's Avatar
    Stephen Paul Guest

    Default Which eyepieces for a fast newtonian?

    "Lawrence Sayre" <> wrote in message

    Hey, that's pretty good. Still, the Nagler isn't exactly enough more
    expensive to warrant robbing a bank. <g>

  8. #8
    Michael McCulloch's Avatar
    Michael McCulloch Guest

    Default Which eyepieces for a fast newtonian?

    On Tue, 17 Feb 2004 16:26:50 GMT, "Stephen Paul"
    <> wrote:

    Which focal length? I had the 21XL and obtained a 20XW. I found no
    difference in blackout and kept the 20XW.

    Michael McCulloch

  9. #9
    Stephen Paul's Avatar
    Stephen Paul Guest

    Default Which eyepieces for a fast newtonian?

    "Michael McCulloch" <> wrote in message

    I believe it was the 10mm, although frankly it might have been the 14mm. If
    the owner doesn't bail on them, I'll get another chance to evaluate them
    further (he has the full set), but my first experience wasn't immediately
    great regarding comfort (unlike the 10.5mm XL, which is immediately

    As Del said [paraphrase], comfortable ("easy view") means you don't have to
    think about the eyepiece to get the best it has to offer. When I looked into
    the XW, I made the comment to the owner that I wasn't able to enjoy the
    view, because I was too busy thinking about the eyepiece. I was happy when
    he switched to the Orthos, which we then compared to Radians. Both of the
    latter being more "easy view".

    As for the NT6's, I have "every session" experience with those, since they
    are my primary eyepieces at 111x, 160x and 205x. These are not problem free
    either, but my first impression of the XW leaves me preferring the NT6's.

    I should also point out (and I indicated this in my initial response) that
    given a comfortable seating position and eyepiece orientation, the blackouts
    might not be a problem, so try before you buy. My goal here is to reveal to
    the reader, out of my own experience, what to watch for when evaluating the

    Can you describe the conditions around which blackout occurs in the 21?

    I'd also like to know what other people think of the Nag T6s concerning any
    weaknesses. The only ones that I'm aware of are lateral color, and the fact
    that the eye relief seems to be right at the 82 degree mark. Any closer in
    and the center blacks out. Any farther out, and the field stop is hidden
    behind the external stop on the eye lens.

    Personally, this is one of the strengths of saa. The ability to share
    different perspectives and experiences with the same equipment. Just don't
    take anyone's review as gospel. Instead, armed with knowledge, go and
    evaluate for yourself. No two people will see things exactly the same.

    Enjoy your XW!!! There's not much doubt that it's one of the better
    eyepieces on the market!!


  10. #10
    Mike Fitterman's Avatar
    Mike Fitterman Guest

    Default Which eyepieces for a fast newtonian?

    "Stephen Paul" <> wrote in message

    Steve, I have found that when I put the eyecups for the XWs into the
    matching configuration that I have on my XL they are much closer in terms of
    blackouts. Leaving the eyecups up and not being able to press against the
    eyecups (which is how these eyepieces are designed) causes all sorts of
    blackout problems. I'll have to try this on the XL and see if it has this
    same problem.


    This would have been a better comparison if we had put the pentax XWs in the
    same scope! I don't believe we used the Pentax in the Televue. This would
    have provided more comfort and a better comparison. Unfortunately, without
    having rotating rings, the long tube newt on a gem just doesn't cut it for
    comfortable observing if your not willing to rotate the tube.


    I've found that the NT6's have a slightly duller image than the XWs although
    we will have to try them side by side because this is only a memory.


    We need to try this experiment between the Naglers, Radians and Pentaxs
    (with the eyecups down) and see if there is a significant difference.



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